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class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Semi-quantitative model describing interactions between acids and bases of Lewis</div> <p>In <a href="/wiki/Chemistry" title="Chemistry">chemistry</a>, the <b>ECW model</b> is a semi-quantitative model that describes and predicts the strength of <a href="/wiki/Lewis_acid" class="mw-redirect" title="Lewis acid">Lewis acid</a>–<a href="/wiki/Lewis_base" class="mw-redirect" title="Lewis base">Lewis base</a> interactions. Many <a href="/wiki/Chemical_reaction" title="Chemical reaction">chemical reactions</a> can be described as <a href="/wiki/Acid%E2%80%93base_reaction" title="Acid–base reaction">acid–base reactions</a>, so models for such interactions are of potentially broad interest. The model initially assigned <b>E and C parameters</b> to each and every acid and base. The model was later expanded to <i>the ECW model</i> to cover reactions that have a constant energy term, <i>W</i>, which describes processes that precede the acid–base reaction. This quantitative model is often discussed with the qualitative <a href="/wiki/HSAB_theory" title="HSAB theory">HSAB theory</a>, which also seeks to rationalize the behavior of diverse acids and bases. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History_of_the_problem">History of the problem</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=1" title="Edit section: History of the problem"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As early as 1938, <a href="/wiki/G._N._Lewis" class="mw-redirect" title="G. N. Lewis">G. N. Lewis</a> pointed out that the relative strength of an acid or base depended upon the base or acid against which it was measured.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> No single rank order of acid or base strength can predict the energetics of the cross reaction. Consider the following pair of acid–base reactions:. </p> <dl><dd>4F-C<sub>6</sub>H<sub>4</sub>OH + OEt<sub>2</sub> −Δ<i>H</i> = 5.94 kcal/mole</dd> <dd>4F-C<sub>6</sub>H<sub>4</sub>OH + SMe<sub>2</sub> −Δ<i>H</i> = 4.73 kcal/mole</dd></dl> <p>These data suggest that OEt<sub>2</sub> is a stronger base than SMe<sub>2</sub>. The opposite is found, however, when I<sub>2</sub> is the acid: </p> <dl><dd>I<sub>2</sub> + OEt<sub>2</sub> −Δ<i>H</i> = 4.16 kcal/mole</dd> <dd>I<sub>2</sub> + SMe<sub>2</sub> −Δ<i>H</i> = 7.63 kcal/mole</dd></dl> <div class="mw-heading mw-heading2"><h2 id="E_and_C_equation"><i>E</i> and <i>C</i> equation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=2" title="Edit section: E and C equation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <i>E</i>-<i>C</i> model accommodates the failure of single parameter descriptions of acids and bases. In 1965 <a href="/wiki/Russell_S._Drago" title="Russell S. Drago">Russell S. Drago</a> and Bradford Wayland published the two term equation such that each acid and each base is described by two parameters.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Each acid is characterized by an <i>E</i><sub>A</sub> and a <i>C</i><sub>A</sub>. Each base is likewise characterized by its own <i>E</i><sub>B</sub> and <i>C</i><sub>B</sub>. The <i>E</i> and <i>C</i> parameters refer, respectively, to the <a href="/wiki/Ionic_bond" class="mw-redirect" title="Ionic bond">electrostatic</a> and <a href="/wiki/Covalent" class="mw-redirect" title="Covalent">covalent</a> contributions to the <a href="/wiki/Bond_energy" title="Bond energy">strength of the bonds</a> that the acid and base will form. These parameters have been empirically obtained by using enthalpies for adducts that form only <a href="/wiki/Sigma_bond" title="Sigma bond">σ bonds</a> between the acid and base as well as <a href="/wiki/Adducts" class="mw-redirect" title="Adducts">adducts</a> that have no <a href="/wiki/Steric_effects" title="Steric effects">steric repulsion</a> between the acid and base. </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo>−</mo> <mi mathvariant="normal">Δ</mi> <mi>H</mi> <mo>=</mo> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3ee6b5b83826763c2161c9596362a44f8e3d189f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:24.389ex; height:2.509ex;" alt="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}" /></span></dd></dl> <p>This equation reproduces and predicts the <a href="/wiki/Enthalpy" title="Enthalpy">enthalpy</a>, Δ<i>H</i>, of a reaction between many acids and bases. Δ<i>H</i> is a measure of strength of the bond between the acid and the base, both in the gas phase and in weakly solvating media. <a href="/wiki/Entropy" title="Entropy">Entropy</a> effects are ignored. A matrix presentation of the equation enhances its utility.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>Four values, two <i>E</i> and two <i>C</i> were assigned as references. <i>E</i><sub>A</sub> and <i>C</i><sub>A</sub> of <a href="/wiki/Iodine" title="Iodine">I<sub>2</sub></a> were chosen as standards. Since I<sub>2</sub> has little tendency to undergo electrostatic bonding, the <i>E</i><sub>A</sub> parameter was assigned a small value, 0.5, while the value of <i>C</i><sub>A</sub> for the covalent property was set at 2.0. For the two base parameters, <i>E</i><sub>B</sub> for CH<sub>3</sub>C(O)N(CH<sub>3</sub>)<sub>2</sub> (<a href="/wiki/Dimethylacetamide" title="Dimethylacetamide">DMA</a>) was set at 2.35 and <i>C</i><sub>B</sub> for (C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>S, <a href="/wiki/Diethyl_sulfide" title="Diethyl sulfide">diethyl sulfide</a>, was set at 3.92. Fixing the parameters in this way imposed the covalent-electrostatic model on the data set by fixing the <i>E</i><sub>A</sub><i>E</i><sub>B</sub> and <i>C</i><sub>A</sub><i>C</i><sub>B</sub> products of the DMA and (C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>S adducts with iodine, and these four values ensured that none of the parameters had negative values. Due to increasing enthalpy data that became available since the EC equation was first proposed the parameters have been improved. Mixing <i>E</i> and <i>C</i> numbers from the improved set of parameters with older parameters will result in incorrect calculations and is to be avoided.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> A select set of the improved <i>E</i> and <i>C</i> numbers is found in this article and the complete set is available in the literature.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> <i>E</i><sub>B</sub> and <i>C</i><sub>B</sub> parameters for phosphines that can be used in combination with the improved parameters for oxygen, nitrogen, and sulfur donors to measure σ-basicity have been reported.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="ECW_model"><i>ECW</i> model</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=3" title="Edit section: ECW model"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the <i>ECW</i> model, a new term W was added to the equation. </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}+W}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo>−</mo> <mi mathvariant="normal">Δ</mi> <mi>H</mi> <mo>=</mo> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> <mo>+</mo> <mi>W</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}+W}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f902874c3e316fda625461f9e3343beaca81a7c6" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:29.665ex; height:2.509ex;" alt="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}+W}" /></span></dd></dl> <p>The W term represents a constant energy for cleavage of a dimeric acid or base. For example, the enthalpy of cleavage the <a href="/wiki/Rhodium_carbonyl_chloride" title="Rhodium carbonyl chloride">[Rh(CO)<sub>2</sub>Cl]<sub>2</sub></a> by base B involves two steps. The first step is cleavage of the dimer, which is <i>W</i>: </p> <dl><dd><style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span> [Rh(CO)<sub>2</sub>Cl]<sub>2</sub> → Rh(CO)<sub>2</sub>Cl <span style="padding-left:1.0em;"> </span> <i>W</i> = −10.39 kcal/mol</dd></dl> <p>The second step is the binding of B to RhCl(CO)<sub>2</sub> monomer. In this case, <i>W</i> = −10.39 kcal/mol. </p><p>In other cases, W is the enthalpy needed to cleave the internal hydrogen bonding of the H-bonding acid <a href="/wiki/Nonafluoro-tert-butyl_alcohol" title="Nonafluoro-tert-butyl alcohol">(CF<sub>3</sub>)<sub>3</sub>COH</a>. W is also useful for a base displacement reaction in poorly solvating media: </p> <dl><dd>F<sub>3</sub>B-OEt<sub>2</sub> → BF<sub>3</sub> + OEt<sub>2</sub></dd></dl> <p>For any base, a constant energy contribution is observed for the breaking of the <a href="/wiki/Boron_trifluoride_etherate" title="Boron trifluoride etherate">F<sub>3</sub>B-OEt<sub>2</sub></a> bond. An ECW study of the enthalpies of a series of bases produces a W value that corresponds to the enthalpy of dissociation of the F<sub>3</sub>B-OEt<sub>2</sub> bond. The <i>E</i><sub>A</sub> and <i>C</i><sub>A</sub> parameters that result are those for uncomplexed BF<sub>3</sub>. </p> <div class="mw-heading mw-heading2"><h2 id="A_graphical_presentation_of_the_ECW_model">A graphical presentation of the <i>ECW</i> model</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=4" title="Edit section: A graphical presentation of the ECW model"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A graphical presentation of this model clearly shows that there is no single rank order of acid or base strength, a point often overlooked, and emphasizes that the magnitude of acid and base interactions requires two parameters (<i>E</i> & <i>C</i>) to account for the interactions.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>The EC equation from the ECW Model </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo>−</mo> <mi mathvariant="normal">Δ</mi> <mi>H</mi> <mo>=</mo> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>A</mi> </mrow> </msub> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>B</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3ee6b5b83826763c2161c9596362a44f8e3d189f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:24.389ex; height:2.509ex;" alt="{\displaystyle -\Delta H=E_{A}E_{B}+C_{A}C_{B}}" /></span></dd></dl> <p>can be rearranged into a form which can be plotted as a straight line. </p> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:ECW_Model_Graph.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/ECW_Model_Graph.png/512px-ECW_Model_Graph.png" decoding="async" width="512" height="316" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/ECW_Model_Graph.png/768px-ECW_Model_Graph.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7b/ECW_Model_Graph.png/1024px-ECW_Model_Graph.png 2x" data-file-width="2561" data-file-height="1583" /></a><figcaption>C-B plot using only three Lewis bases to show this graphical approach. </figcaption></figure> <p>In a Cramer–Bopp plot for Lewis bases, the parameter <i>R<sub>a</sub></i><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup> reflects the mode of bonding of a potential Lewis acid partner, from purely electrostatic interactions (<span class="texhtml texhtml-big" style="font-size:100%;"><i>R</i><sub>a</sub> = −1</span>) to purely covalent interactions (<span class="texhtml texhtml-big" style="font-size:100%;"><i>R</i><sub>a</sub> = +1</span>). The parameter <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \scriptstyle {\frac {-\Delta H}{E_{a}+C_{a}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mstyle displaystyle="false" scriptlevel="1"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mo>−</mo> <mi mathvariant="normal">Δ</mi> <mi>H</mi> </mrow> <mrow> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>a</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>a</mi> </mrow> </msub> </mrow> </mfrac> </mrow> </mstyle> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \scriptstyle {\frac {-\Delta H}{E_{a}+C_{a}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9b3886d8cb65a98e81908b0487b7c032110d4b5f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.505ex; width:5.491ex; height:3.676ex;" alt="{\displaystyle \scriptstyle {\frac {-\Delta H}{E_{a}+C_{a}}}}" /></span> reflects the strength of the bonding interaction. The plot shown here allows comparison of three chosen Lewis bases: <a href="/wiki/Acetonitrile" title="Acetonitrile">acetonitrile</a>, <a href="/wiki/Ammonia" title="Ammonia">ammonia</a>, and <a href="/wiki/Dimethyl_sulfide" title="Dimethyl sulfide">dimethyl sulfide</a>. The Lewis acid iodine (<span class="texhtml texhtml-big" style="font-size:100%;"><i>R</i><sub>a</sub> = 0.6</span>) will interact most strongly with dimethyl sulfide and least strongly with acetonitrile, whereas <a href="/wiki/Triethylgallium" title="Triethylgallium">triethylgallium</a> (<span class="texhtml texhtml-big" style="font-size:100%;"><i>R</i><sub>a</sub> = −0.65</span>) will interact most strongly with ammonia and least strongly with dimethyl sulfide. The plot also shows that ammonia is a stronger Lewis base than acetonitrile irrespective of its Lewis acid partner, whereas the relative strengths of ammonia and dimethyl sulfide as Lewis bases depends on the bonding characteristics of the Lewis acid, swapping order when <span class="texhtml texhtml-big" style="font-size:100%;"><i>R</i><sub>a</sub> = 0.1</span>. <span class="cleanup-needed-content" style="padding-left:0.1em; padding-right:0.1em; color:var(--color-subtle, #54595d); border:1px solid var(--border-color-subtle, #c8ccd1);">(NB: guesstimate).</span><sup class="noprint Inline-Template" style="margin-left:0.1em; white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="The text near this tag may need clarification or removal of jargon. (June 2021)">clarification needed</span></a></i>]</sup> The Cramer–Bopp plot was developed as a visual tool for comparing Lewis base strength with the range of possible Lewis acid partners, and a similar plot can be constructed to examine selected Lewis acids against the range of possible Lewis bases. References 5, 8, 12, and 14 contain graphical presentations that define the ranking order of strength of many Lewis acids and bases. </p> <div class="mw-heading mw-heading2"><h2 id="Other_aspects_and_extensions_of_the_ECW_model">Other aspects and extensions of the <i>ECW</i> model</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=5" title="Edit section: Other aspects and extensions of the ECW model"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As mentioned above the <i>E</i> and <i>C</i> parameters are obtained from enthalpies of adduct formation in which the bond between the acid and base is a σ interaction and adducts that have no steric repulsion between the acid and base. As a result, <i>E</i> and <i>C</i> parameters can be used to glean information about <a href="/wiki/Pi_bond" title="Pi bond">pi bonding</a>. When pi bonding contributes to the measured enthalpy, the enthalpy calculated from the <i>E</i> and <i>C</i> parameters will be less than the measured enthalpy and the difference provides a measure of the extent of the pi bonding contribution.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>The ᐃH calculated for the reaction of <a href="/wiki/Trimethylborane" title="Trimethylborane">Me<sub>3</sub>B</a> with Me<sub>3</sub>N is larger than the observed. This discrepancy is attributed to steric repulsion between the methyl groups on the B and N. The difference between the calculated and observed values can then be taken as the amount of the <a href="/wiki/Steric_effect" class="mw-redirect" title="Steric effect">steric effect</a>, a value otherwise not attainable. Steric effects have also been identified with <a href="/wiki/Trimethyltin_chloride" title="Trimethyltin chloride">(CH<sub>3</sub>)<sub>3</sub>SnCl</a> and with <a href="/wiki/Hexafluoroacetylacetone" title="Hexafluoroacetylacetone">Cu(HFacac)<sub>2</sub></a>. </p><p>The use of <i>E</i> and <i>C</i> parameters have been extended to analyze spectroscopic changes occurring during adduct formation.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> For example, the shift of the phenol OH stretching frequency, <span class="texhtml texhtml-big" style="font-size:100%;">Δ<i>χ</i></span>, that occurs upon adduct formation has been analyzed using the following equation: </p> <dl><dd><span class="texhtml">Δ<i>χ</i> = <i>Ε<sub>A</sub></i><sup>∗</sup><i>E<sub>B</sub></i> + <i>C<sub>A</sub></i><sup>∗</sup><i>C<sub>B</sub></i> + <i>W</i><sup>∗</sup></span></dd></dl> <p>where asterisks on the <i>E</i><sub>A</sub> and <i>C</i><sub>A</sub> for phenol indicate that the acceptor is held constant and the frequency shift is measured as the base is varied. The asterisks also indicate that the phenol parameters are those for frequency shifts and not those for enthalpies. An analysis like this provides a basis for using <i>E</i><sub>B</sub> and <i>C</i><sub>B</sub> parameters as a reference scale of donor strengths for frequency shifts. This type analysis has also been applied to other spectroscopic shifts (<a href="/wiki/Nuclear_magnetic_resonance" title="Nuclear magnetic resonance">NMR</a>, <a href="/wiki/Electron_paramagnetic_resonance" title="Electron paramagnetic resonance">EPR</a>, <a href="/wiki/Ultraviolet%E2%80%93visible_spectroscopy" title="Ultraviolet–visible spectroscopy">UV-vis</a>, <a href="/wiki/Infrared_spectroscopy" title="Infrared spectroscopy">IR</a>, etc.) accompanying adduct formation. Any physicochemical property, <span class="texhtml texhtml-big" style="font-size:100%;">Δ<i>χ</i></span>, that is dominated by σ donor-acceptor interaction can be correlated with the enthalpy-derived <i>E</i> and <i>C</i> parameters. </p><p>The <i>ECW</i> equations enables one to correlate and predict the enthalpies of adduct formation of neutral donor-acceptor interactions for which the electron-transfer is limited. For gas-phase reactions between cations and neutral donors, there is significant electron-transfer. The extension of the <i>ECW</i> model to cation-neutral Lewis base interactions has led to the <i>ECT</i> model.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Others have concluded that the ECW model "is generally found helpful in many fields of solution chemistry and biochemistry".<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <table> <tbody><tr style="vertical-align:top;"> <td> <table class="wikitable"> <caption>Selected <i>E</i> and <i>C</i> parameters for acids<sup id="cite_ref-aa_16-0" class="reference"><a href="#cite_note-aa-16"><span class="cite-bracket">[</span>b<span class="cite-bracket">]</span></a></sup> </caption> <tbody><tr> <th>Acid </th> <th><i>E</i><sub>A</sub> </th> <th><i>C</i><sub>A</sub> </th> <th>W </th> <th><i>C</i><sub>A</sub>/<i>E</i><sub>A</sub> </th></tr> <tr> <td><a href="/wiki/Iodine" title="Iodine">I<sub>2</sub></a></td> <td>0.50</td> <td>2.0</td> <td>0</td> <td>4.0 </td></tr> <tr> <td><a href="/wiki/Iodine_monobromide" title="Iodine monobromide">IBr</a></td> <td>1.20</td> <td>3.29</td> <td>0</td> <td>2.7 </td></tr> <tr> <td><a href="/wiki/Iodine_monochloride" title="Iodine monochloride">ICl</a></td> <td>2.92</td> <td>1.66</td> <td>0</td> <td>0.57 </td></tr> <tr> <td><a href="/wiki/Phenol" title="Phenol">C<sub>6</sub>H<sub>5</sub>OH</a></td> <td>2.27</td> <td>1.07</td> <td>0</td> <td>0.47 </td></tr> <tr> <td>4-FC<sub>6</sub>H<sub>4</sub>OH</td> <td>2.30</td> <td>1.11</td> <td>0</td> <td>0.48 </td></tr> <tr> <td>3-CF<sub>3</sub>C<sub>6</sub>H<sub>4</sub>OH</td> <td>2.38</td> <td>1.22</td> <td>0</td> <td>0.51 </td></tr> <tr> <td><a href="/wiki/P-Cresol" title="P-Cresol">4-CH<sub>3</sub>C<sub>6</sub>H<sub>4</sub>OH</a></td> <td>2.23</td> <td>1.03</td> <td>0</td> <td>0.44 </td></tr> <tr> <td><a href="/wiki/2,2,2-Trifluoroethanol" title="2,2,2-Trifluoroethanol">CF<sub>3</sub>CH<sub>2</sub>OH</a></td> <td>2.07</td> <td>1.06</td> <td>0</td> <td>0.51 </td></tr> <tr> <td><a href="/wiki/Hexafluoro-2-propanol" title="Hexafluoro-2-propanol">(CF<sub>3</sub>)<sub>2</sub>CHOH</a></td> <td>2.89</td> <td>1.33</td> <td>−0.16</td> <td>0.46 </td></tr> <tr> <td><a href="/wiki/Tert-Butyl_alcohol" title="Tert-Butyl alcohol">(CH<sub>3</sub>)<sub>3</sub>COH</a></td> <td>1.07</td> <td>0.69</td> <td>0</td> <td>0.65 </td></tr> <tr> <td><a href="/wiki/Nonafluoro-tert-butyl_alcohol" title="Nonafluoro-tert-butyl alcohol">(CF<sub>3</sub>)<sub>3</sub>COH</a></td> <td>3.06</td> <td>1.88</td> <td>−0.87</td> <td>0.61 </td></tr> <tr> <td><a href="/wiki/1-Octanol" title="1-Octanol">C<sub>8</sub>H<sub>17</sub>OH</a></td> <td>0.85</td> <td>0.87</td> <td>0</td> <td>1.0 </td></tr> <tr> <td><a href="/wiki/Chloroform" title="Chloroform">HCCl<sub>3</sub></a></td> <td>1.56</td> <td>0.44</td> <td>0</td> <td>0.28 </td></tr> <tr> <td><a href="/wiki/Methylene_chloride" class="mw-redirect" title="Methylene chloride">CH<sub>2</sub>Cl<sub>2</sub></a></td> <td>0.86</td> <td>0.11</td> <td>0</td> <td>0.13 </td></tr> <tr> <td><a href="/wiki/Pyrrole" title="Pyrrole">C<sub>4</sub>H<sub>4</sub>NH</a></td> <td>1.38</td> <td>0.68</td> <td>0</td> <td>0.49 </td></tr> <tr> <td><a href="/wiki/Isocyanic_acid" title="Isocyanic acid">HNCO</a></td> <td>1.60</td> <td>0.69</td> <td>0</td> <td>0.43 </td></tr> <tr> <td><a href="/wiki/Isothiocyanic_acid" class="mw-redirect" title="Isothiocyanic acid">HNCS</a></td> <td>2.85</td> <td>0.70</td> <td>0</td> <td>0.25 </td></tr> <tr> <td><a href="/wiki/Trimethylborane" title="Trimethylborane">B(CH<sub>3</sub>)<sub>3</sub></a></td> <td>2.90</td> <td>3.60</td> <td>0</td> <td>1.2 </td></tr> <tr> <td><a href="/wiki/Trimethylaluminium" title="Trimethylaluminium">Al(CH<sub>3</sub>)<sub>3</sub></a></td> <td>8.66</td> <td>3.68</td> <td>0</td> <td>0.43 </td></tr> <tr> <td><a href="/wiki/Triethylgallium" title="Triethylgallium">Ga(C<sub>2</sub>H<sub>5</sub>)<sub>3</sub></a></td> <td>6.95</td> <td>1.48</td> <td>0</td> <td>0.21 </td></tr> <tr> <td><a href="/wiki/Trimethylindium" title="Trimethylindium">In(CH<sub>3</sub>)<sub>3</sub></a></td> <td>6.60</td> <td>2.15</td> <td>0</td> <td>0.33 </td></tr> <tr> <td><a href="/wiki/Trimethyltin_chloride" title="Trimethyltin chloride">(CH<sub>3</sub>)<sub>3</sub>SnCl</a></td> <td>2.87</td> <td>0.71</td> <td>0</td> <td>0.25 </td></tr> <tr> <td><a href="/wiki/Sulfur_dioxide" title="Sulfur dioxide">SO<sub>2</sub></a></td> <td>0.51</td> <td>1.56</td> <td>0</td> <td>3.1 </td></tr> <tr> <td><a href="/wiki/Antimony_pentachloride" title="Antimony pentachloride">SbCl<sub>5</sub></a></td> <td>3.64</td> <td>10.42</td> <td>0</td> <td>2.9 </td></tr> <tr> <td><a href="/wiki/Hexafluoroacetylacetone" title="Hexafluoroacetylacetone">Cu(HFacac)<sub>2</sub></a><sup id="cite_ref-ab_17-0" class="reference"><a href="#cite_note-ab-17"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup></td> <td>1.82</td> <td>2.86</td> <td>0</td> <td>1.6 </td></tr> <tr> <td><a href="/wiki/Zinc_bis(bis(trimethylsilyl)amide)" class="mw-redirect" title="Zinc bis(bis(trimethylsilyl)amide)">Zn[N(Si(CH<sub>3</sub>)<sub>3</sub>]<sub>2</sub></a></td> <td>2.75</td> <td>2.32</td> <td>0</td> <td>0.84 </td></tr> <tr> <td><a href="/wiki/Cadmium_bis(bis(trimethylsilyl)amide)" class="mw-redirect" title="Cadmium bis(bis(trimethylsilyl)amide)">Cd[N(Si(CH<sub>3</sub>)<sub>3</sub>]<sub>2</sub></a></td> <td>2.50</td> <td>1.83</td> <td>0</td> <td>0.73 </td></tr> <tr> <td>Zn<a href="/wiki/Tetraphenylporphyrin" title="Tetraphenylporphyrin">TPP</a><sup id="cite_ref-ac_18-0" class="reference"><a href="#cite_note-ac-18"><span class="cite-bracket">[</span>d<span class="cite-bracket">]</span></a></sup></td> <td>2.72</td> <td>1.45</td> <td>0</td> <td>0.53 </td></tr> <tr> <td>Co<a href="/wiki/Protoporphyrin_IX" title="Protoporphyrin IX">PPIX</a>DME<sup id="cite_ref-ad_19-0" class="reference"><a href="#cite_note-ad-19"><span class="cite-bracket">[</span>e<span class="cite-bracket">]</span></a></sup></td> <td>2.32</td> <td>1.34</td> <td>0</td> <td>0.58 </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span>[MeCo(<a href="/wiki/Dimethylglyoxime" title="Dimethylglyoxime">Hdmg</a>)<sub>2</sub>]<sub>2</sub><sup id="cite_ref-ae_20-0" class="reference"><a href="#cite_note-ae-20"><span class="cite-bracket">[</span>f<span class="cite-bracket">]</span></a></sup></td> <td>4.70</td> <td>3.24</td> <td>−5.84</td> <td>0.60 </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span><a href="/wiki/Rhodium_carbonyl_chloride" title="Rhodium carbonyl chloride">[Rh(CO)<sub>2</sub>Cl]<sub>2</sub></a></td> <td>4.32</td> <td>4.13</td> <td>−10.39</td> <td>0.96 </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span><a href="/wiki/Cyclooctadiene_rhodium_chloride_dimer" title="Cyclooctadiene rhodium chloride dimer">[Rh(COD)<sub>2</sub>Cl]<sub>2</sub></a></td> <td>2.43</td> <td>2.56</td> <td>−5.78</td> <td>1.1 </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span><a href="/wiki/Allylpalladium_chloride_dimer" title="Allylpalladium chloride dimer">[Pd(π-ally)Cl]<sub>2</sub></a></td> <td>1.70</td> <td>2.14</td> <td>−3.38</td> <td>1.3 </td></tr> <tr> <td>[Ni(TFAcCAM)<sub>2</sub>]<sub>2</sub><sup id="cite_ref-af_21-0" class="reference"><a href="#cite_note-af-21"><span class="cite-bracket">[</span>g<span class="cite-bracket">]</span></a></sup></td> <td>1.55</td> <td>1.32</td> <td>0</td> <td>0.85 </td></tr> <tr> <td>Mo<sub>2</sub>PFB<sub>4</sub><sup id="cite_ref-ag_22-0" class="reference"><a href="#cite_note-ag-22"><span class="cite-bracket">[</span>h<span class="cite-bracket">]</span></a></sup></td> <td>3.15</td> <td>1.05</td> <td>0</td> <td>0.33 </td></tr></tbody></table> </td> <td> <table class="wikitable"> <caption>and for bases<sup id="cite_ref-ba_23-0" class="reference"><a href="#cite_note-ba-23"><span class="cite-bracket">[</span>i<span class="cite-bracket">]</span></a></sup> </caption> <tbody><tr> <th>Base </th> <th><i>E</i><sub>B</sub> </th> <th><i>C</i><sub>B</sub> </th> <th><i>C</i><sub>B</sub>/<i>E</i><sub>B</sub> </th></tr> <tr> <td><a href="/wiki/Ammonia" title="Ammonia">NH<sub>3</sub></a></td> <td>2.31</td> <td>2.04</td> <td>0.88 </td></tr> <tr> <td><a href="/wiki/Methylamine" title="Methylamine">NH<sub>2</sub>(CH<sub>3</sub>)</a></td> <td>2.16</td> <td>3.13</td> <td>1.4 </td></tr> <tr> <td><a href="/wiki/Dimethylamine" title="Dimethylamine">NH(CH<sub>3</sub>)<sub>2</sub></a></td> <td>1.80</td> <td>4.21</td> <td>2.3 </td></tr> <tr> <td><a href="/wiki/Trimethylamine" title="Trimethylamine">N(CH<sub>3</sub>)<sub>3</sub></a></td> <td>1.21</td> <td>5.61</td> <td>4.6 </td></tr> <tr> <td><a href="/wiki/Quinuclidine" title="Quinuclidine">HC(C<sub>2</sub>H<sub>4</sub>)<sub>3</sub>N</a></td> <td>0.80</td> <td>6.72</td> <td>8.4 </td></tr> <tr> <td><a href="/wiki/Triethylamine" title="Triethylamine">(C<sub>2</sub>H<sub>5</sub>)<sub>3</sub>N</a></td> <td>1.32</td> <td>5.73</td> <td>4.3 </td></tr> <tr> <td>1-CH<sub>3</sub>NC<sub>3</sub>N<sup id="cite_ref-ah_24-0" class="reference"><a href="#cite_note-ah-24"><span class="cite-bracket">[</span>j<span class="cite-bracket">]</span></a></sup></td> <td>1.16</td> <td>4.92</td> <td>4.2 </td></tr> <tr> <td><a href="/wiki/Pyridine" title="Pyridine">C<sub>5</sub>H<sub>5</sub>N</a></td> <td>1.78</td> <td>3.54</td> <td>2.0 </td></tr> <tr> <td><a href="/wiki/3-Methylpyridine" title="3-Methylpyridine">3CH<sub>3</sub>C<sub>5</sub>H<sub>4</sub>N</a></td> <td>1.81</td> <td>3.67</td> <td>2.0 </td></tr> <tr> <td><a href="/wiki/3-Bromopyridine" title="3-Bromopyridine">3BrC<sub>5</sub>H<sub>4</sub>N</a></td> <td>1.66</td> <td>3.08</td> <td>1.9 </td></tr> <tr> <td><a href="/w/index.php?title=4-Methoxypyridine&action=edit&redlink=1" class="new" title="4-Methoxypyridine (page does not exist)">4CH<sub>3</sub>OC<sub>5</sub>H<sub>4</sub>N</a></td> <td>1.83</td> <td>3.83</td> <td>2.1 </td></tr> <tr> <td><a href="/wiki/Acetonitrile" title="Acetonitrile">CH<sub>3</sub>CN</a></td> <td>1.64</td> <td>0.71</td> <td>0.43 </td></tr> <tr> <td>(CH<sub>3</sub>)<sub>2</sub>NCN</td> <td>1.92</td> <td>0.92</td> <td>0.48 </td></tr> <tr> <td><a href="/wiki/Chloroacetonitrile" title="Chloroacetonitrile">ClCH<sub>2</sub>CN</a></td> <td>1.67</td> <td>0.33</td> <td>0.20 </td></tr> <tr> <td><a href="/wiki/Acetone" title="Acetone">CH<sub>3</sub>C(O)CH<sub>3</sub></a></td> <td>1.74</td> <td>1.26</td> <td>0.72 </td></tr> <tr> <td><a href="/wiki/Cyclopentanone" title="Cyclopentanone">(CH<sub>2</sub>)<sub>4</sub>CO</a></td> <td>2.02</td> <td>0.88</td> <td>0.43 </td></tr> <tr> <td><a href="/wiki/Ethyl_acetate" title="Ethyl acetate">CH<sub>3</sub>C(O)OC<sub>2</sub>H<sub>5</sub></a></td> <td>1.62</td> <td>0.98</td> <td>0.61 </td></tr> <tr> <td><a href="/wiki/Dimethylacetamide" title="Dimethylacetamide">CH<sub>3</sub>C(O)N(CH<sub>3</sub>)<sub>2</sub></a></td> <td>2.35</td> <td>1.31</td> <td>0.56 </td></tr> <tr> <td><a href="/wiki/Diethyl_ether" title="Diethyl ether">(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>O</a></td> <td>1.80</td> <td>1.63</td> <td>0.91 </td></tr> <tr> <td><a href="/wiki/Tetrahydrofuran" title="Tetrahydrofuran">(CH<sub>2</sub>)<sub>4</sub>O</a></td> <td>1.64</td> <td>2.18</td> <td>1.3 </td></tr> <tr> <td><a href="/wiki/1,4-Dioxane" title="1,4-Dioxane">O(C<sub>2</sub>H<sub>4</sub>)<sub>2</sub>)O</a></td> <td>1.86</td> <td>1.29</td> <td>0.69 </td></tr> <tr> <td>(CH<sub>2</sub>)<sub>4</sub>(CH)<sub>2</sub>)O<sup id="cite_ref-ak_25-0" class="reference"><a href="#cite_note-ak-25"><span class="cite-bracket">[</span>k<span class="cite-bracket">]</span></a></sup></td> <td>1.45</td> <td>2.14</td> <td>1.5 </td></tr> <tr> <td><a href="/wiki/Dimethyl_sulfide" title="Dimethyl sulfide">(CH<sub>3</sub>)<sub>2</sub>S</a></td> <td>0.25</td> <td>3.75</td> <td>15 </td></tr> <tr> <td><a href="/wiki/Tetrahydrothiophene" title="Tetrahydrothiophene">(CH<sub>2</sub>)<sub>4</sub>S</a></td> <td>0.26</td> <td>4.07</td> <td>16 </td></tr> <tr> <td><a href="/wiki/Diethyl_sulfide" title="Diethyl sulfide">(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>S</a></td> <td>0.24</td> <td>3.92</td> <td>16 </td></tr> <tr> <td><a href="/wiki/Dimethyl_sulfoxide" title="Dimethyl sulfoxide">(CH<sub>3</sub>)<sub>2</sub>SO</a></td> <td>2.40</td> <td>1.47</td> <td>0.61 </td></tr> <tr> <td><a href="/w/index.php?title=Tetrahydrothiophene_1-oxide&action=edit&redlink=1" class="new" title="Tetrahydrothiophene 1-oxide (page does not exist)">(CH<sub>2</sub>)<sub>4</sub>SO</a></td> <td>2.44</td> <td>1.64</td> <td>0.67 </td></tr> <tr> <td><a href="/wiki/Pyridine-N-oxide" title="Pyridine-N-oxide">C<sub>5</sub>H<sub>5</sub>NO</a></td> <td>2.29</td> <td>2.33</td> <td>1.0 </td></tr> <tr> <td>4‑CH<sub>3</sub>OC<sub>5</sub>H<sub>4</sub>NO</td> <td>2.34</td> <td>3.02</td> <td>1,3 </td></tr> <tr> <td><a href="/wiki/Triphenylphosphine_oxide" title="Triphenylphosphine oxide">(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO</a></td> <td>2.59</td> <td>1.67</td> <td>0.64 </td></tr> <tr> <td><a href="/wiki/Trimethylphosphine" title="Trimethylphosphine">(CH<sub>3</sub>)<sub>3</sub>P</a></td> <td>0.25</td> <td>5.81</td> <td>24 </td></tr> <tr> <td><a href="/wiki/Trimethyl_phosphite" title="Trimethyl phosphite">(CH<sub>3</sub>O)<sub>3</sub>P</a></td> <td>0.13</td> <td>4.83</td> <td>37 </td></tr> <tr> <td><a href="/wiki/Dimethyl_selenide" title="Dimethyl selenide">(CH<sub>3</sub>)<sub>2</sub>Se</a></td> <td>0.05</td> <td>4.24</td> <td>83 </td></tr> <tr> <td><a href="/wiki/Triphenylphosphine_sulfide" title="Triphenylphosphine sulfide">(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PS</a></td> <td>0.35</td> <td>3.65</td> <td>10 </td></tr> <tr> <td><a href="/wiki/Benzene" title="Benzene">C<sub>6</sub>H<sub>6</sub></a></td> <td>0.70</td> <td>0.45</td> <td>0.64 </td></tr></tbody></table> </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Charge-transfer_complexes_of_I2">Charge-transfer complexes of I<sub>2</sub></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=6" title="Edit section: Charge-transfer complexes of I2"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The enthalpies of formation of some Donor-I<sub>2</sub> adducts are listed below. I<sub>2</sub> is a Lewis acid classified as a <a href="/wiki/HSAB_theory" title="HSAB theory">soft acid</a> and its acceptor properties are discussed in the ECW model. The relative acceptor strength of I<sub>2</sub> toward a series of bases, versus other Lewis acids, can be illustrated by C-B plots.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable"> <caption>Enthalpies of formation of some donor-I<sub>2</sub> adducts </caption> <tbody><tr> <th>Base </th> <th>−Δ<i>H</i> (kcal/mol) </th></tr> <tr> <td>Benzene</td> <td>1.4 </td></tr> <tr> <td>Toluene</td> <td>1.8 </td></tr> <tr> <td>Dioxane</td> <td>3.5 </td></tr> <tr> <td>Diethyl ether</td> <td>4.3 </td></tr> <tr> <td>Diethyl sulfide</td> <td>8.3 </td></tr> <tr> <td>Dimethylacetamide</td> <td>4.7 </td></tr> <tr> <td>Acetonitrile</td> <td>1.9 </td></tr> <tr> <td>Pyridine</td> <td>7.80 </td></tr> <tr> <td>Triethylamine</td> <td>12.0 </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=7" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Acid%E2%80%93base_reaction" title="Acid–base reaction">Acid–base reaction</a></li> <li><a href="/wiki/Lewis_acid" class="mw-redirect" title="Lewis acid">Lewis acid</a>–<a href="/wiki/Lewis_base" class="mw-redirect" title="Lewis base">Lewis base</a></li> <li><a href="/wiki/Acid" title="Acid">Acid</a></li> <li><a href="/wiki/Russell_S._Drago" title="Russell S. Drago">Russell S. Drago</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=8" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">(<i>C</i><sub>A</sub> − <i>E</i><sub>A</sub>)/(<i>C</i><sub>A</sub> + <i>E</i><sub>A</sub>)</span> </li> <li id="cite_note-aa-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-aa_16-0">^</a></b></span> <span class="reference-text"> units for <i>E<sub>A</sub></i>, and <i>C<sub>A</sub></i> are (kcal/mol)<sup><style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span></sup> and W is kcal/mol</span> </li> <li id="cite_note-ab-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-ab_17-0">^</a></b></span> <span class="reference-text"> <a href="/wiki/Hexafluoroacetylacetone" title="Hexafluoroacetylacetone">bis(hexafloroacetylacetonato)copper(II)</a></span> </li> <li id="cite_note-ac-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-ac_18-0">^</a></b></span> <span class="reference-text"> zinc <a href="/wiki/Tetraphenylporphine" class="mw-redirect" title="Tetraphenylporphine">tetraphenylporphine</a></span> </li> <li id="cite_note-ad-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-ad_19-0">^</a></b></span> <span class="reference-text"> <a href="/wiki/Protoporphyrin_IX" title="Protoporphyrin IX">cobalt(II) protoporhyrin IX dimethyl ester IX</a></span> </li> <li id="cite_note-ae-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-ae_20-0">^</a></b></span> <span class="reference-text"> <a href="/wiki/Chloro(pyridine)cobaloxime" title="Chloro(pyridine)cobaloxime">methylcobaloxime</a></span> </li> <li id="cite_note-af-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-af_21-0">^</a></b></span> <span class="reference-text"> bis(3-trifluoro-d-camphorate)nickel(II) dimer</span> </li> <li id="cite_note-ag-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-ag_22-0">^</a></b></span> <span class="reference-text"> <a href="/wiki/Molybdenum" title="Molybdenum">molybdenum perfluorobutyrate</a></span> </li> <li id="cite_note-ba-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-ba_23-0">^</a></b></span> <span class="reference-text"> Units for <i>E</i><sub>B</sub> and <i>C</i><sub>B</sub> are <a href="/wiki/Kilocalorie_per_mole" title="Kilocalorie per mole">(kcal/mol)</a><sup><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027" /><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span></sup></span> </li> <li id="cite_note-ah-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-ah_24-0">^</a></b></span> <span class="reference-text"> <a href="/wiki/1-Methylimidazole" title="1-Methylimidazole">N-methylimidazole</a></span> </li> <li id="cite_note-ak-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-ak_25-0">^</a></b></span> <span class="reference-text"> 7-Oxabicyclo[2.2.1]heptane</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ECW_model&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626" /><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text">Lewis G. N. (1938) Acids and bases Journal of the Franklin Institute, 226, 293-313.</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFDrago,_R._S.Wayland,_B._B.1965" class="citation journal cs1">Drago, R. S.; Wayland, B. B. (1965). "A Double-Scale Equation for Correlating Enthalpies of Lewis Acid-Base Interactions". <i>Journal of the American Chemical Society</i>. <b>87</b> (16): <span class="nowrap">3571–</span>3577. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja01094a008">10.1021/ja01094a008</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Chemical+Society&rft.atitle=A+Double-Scale+Equation+for+Correlating+Enthalpies+of+Lewis+Acid-Base+Interactions&rft.volume=87&rft.issue=16&rft.pages=%3Cspan+class%3D%22nowrap%22%3E3571-%3C%2Fspan%3E3577&rft.date=1965&rft_id=info%3Adoi%2F10.1021%2Fja01094a008&rft.au=Drago%2C+R.+S.&rft.au=Wayland%2C+B.+B.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Vogel,_G._C.Needham,_T._E.1971" class="citation journal cs1">Drago, R. S.; Vogel, G. C.; Needham, T. E. (1971). "A Four-Parameter Equation for Predicting Enthalpies of Adduct Formation". <i>Journal of the American Chemical Society</i>. <b>93</b> (23): <span class="nowrap">6014–</span>6026. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja00752a010">10.1021/ja00752a010</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Chemical+Society&rft.atitle=A+Four-Parameter+Equation+for+Predicting+Enthalpies+of+Adduct+Formation&rft.volume=93&rft.issue=23&rft.pages=%3Cspan+class%3D%22nowrap%22%3E6014-%3C%2Fspan%3E6026&rft.date=1971&rft_id=info%3Adoi%2F10.1021%2Fja00752a010&rft.au=Drago%2C+R.+S.&rft.au=Vogel%2C+G.+C.&rft.au=Needham%2C+T.+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Ferris,_D._C..P.Wong,_N..M.1990" class="citation journal cs1">Drago, R. S.; Ferris, D. C..P.; Wong, N..M. (1990). "A method for the analysis and prediction of gas-phase ion-molecule enthalpies". <i>Journal of the American Chemical Society</i>. <b>112</b> (24): 8953–8961–2479. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja00180a047">10.1021/ja00180a047</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Chemical+Society&rft.atitle=A+method+for+the+analysis+and+prediction+of+gas-phase+ion-molecule+enthalpies&rft.volume=112&rft.issue=24&rft.pages=8953-8961-2479&rft.date=1990&rft_id=info%3Adoi%2F10.1021%2Fja00180a047&rft.au=Drago%2C+R.+S.&rft.au=Ferris%2C+D.+C..P.&rft.au=Wong%2C+N..M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFVogel_G._C.Drago,_R._S.1996" class="citation journal cs1">Vogel G. C.; Drago, R. S. (1996). "The ECW Model". <i>Journal of Chemical Education</i>. <b>73</b> (8): <span class="nowrap">701–</span>707. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1996JChEd..73..701V">1996JChEd..73..701V</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fed073p701">10.1021/ed073p701</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Chemical+Education&rft.atitle=The+ECW+Model&rft.volume=73&rft.issue=8&rft.pages=%3Cspan+class%3D%22nowrap%22%3E701-%3C%2Fspan%3E707&rft.date=1996&rft_id=info%3Adoi%2F10.1021%2Fed073p701&rft_id=info%3Abibcode%2F1996JChEd..73..701V&rft.au=Vogel+G.+C.&rft.au=Drago%2C+R.+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Dadmun,_A._P.Vogel,_G._C.1992" class="citation journal cs1">Drago, R. S.; Dadmun, A. P.; Vogel, G. C. (1992). "Addition of new donors to the E and C model". <i>Inorganic Chemistry</i>. <b>32</b> (11): <span class="nowrap">2473–</span>2479. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fic00063a045">10.1021/ic00063a045</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Inorganic+Chemistry&rft.atitle=Addition+of+new+donors+to+the+E+and+C+model.&rft.volume=32&rft.issue=11&rft.pages=%3Cspan+class%3D%22nowrap%22%3E2473-%3C%2Fspan%3E2479&rft.date=1992&rft_id=info%3Adoi%2F10.1021%2Fic00063a045&rft.au=Drago%2C+R.+S.&rft.au=Dadmun%2C+A.+P.&rft.au=Vogel%2C+G.+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Joerg,_S.1996" class="citation journal cs1">Drago, R. S.; Joerg, S. (1996). "Phosphine E<sub>B</sub> and C<sub>B</sub> Values". <i>Journal of the American Chemical Society</i>. <b>118</b> (11): <span class="nowrap">2654–</span>2663. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja953581e">10.1021/ja953581e</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Chemical+Society&rft.atitle=Phosphine+E%3Csub%3EB%3C%2Fsub%3E+and+C%3Csub%3EB%3C%2Fsub%3E+Values&rft.volume=118&rft.issue=11&rft.pages=%3Cspan+class%3D%22nowrap%22%3E2654-%3C%2Fspan%3E2663&rft.date=1996&rft_id=info%3Adoi%2F10.1021%2Fja953581e&rft.au=Drago%2C+R.+S.&rft.au=Joerg%2C+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCramer,_R._E.Bopp,_T._T.1977" class="citation journal cs1">Cramer, R. E.; Bopp, T. T. (1977). "Graphical display of the enthalpies of adduct formation for Lewis acids and bases". <i>Journal of Chemical Education</i>. <b>54</b>: <span class="nowrap">612–</span>613. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fed054p612">10.1021/ed054p612</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Chemical+Education&rft.atitle=Graphical+display+of+the+enthalpies+of+adduct+formation+for+Lewis+acids+and+bases&rft.volume=54&rft.pages=%3Cspan+class%3D%22nowrap%22%3E612-%3C%2Fspan%3E613&rft.date=1977&rft_id=info%3Adoi%2F10.1021%2Fed054p612&rft.au=Cramer%2C+R.+E.&rft.au=Bopp%2C+T.+T.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span> The plots shown in this paper used older parameters. Improved E&C parameters are listed in the tables and in references 5 and 6.</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Bilgrien,_C._J.1988" class="citation journal cs1">Drago, R. S.; Bilgrien, C. J. (1988). "Inductive transfer and coordination of ligands in metal-metal bonded systems". <i>Polyhedron</i>. <b>7</b> (<span class="nowrap">16–</span>17): <span class="nowrap">1453–</span>1468. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FS0277-5387%2800%2981774-X">10.1016/S0277-5387(00)81774-X</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Polyhedron&rft.atitle=Inductive+transfer+and+coordination+of+ligands+in+metal-metal+bonded+systems&rft.volume=7&rft.issue=%3Cspan+class%3D%22nowrap%22%3E16%E2%80%93%3C%2Fspan%3E17&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1453-%3C%2Fspan%3E1468&rft.date=1988&rft_id=info%3Adoi%2F10.1016%2FS0277-5387%2800%2981774-X&rft.au=Drago%2C+R.+S.&rft.au=Bilgrien%2C+C.+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.1982" class="citation journal cs1">Drago, R. S. (1982). "The question of a synergistic metal-metal interaction leading to .pi.-back-bond stabilization in dirhodium tetrabutyrate adducts". <i>Inorg. Chem</i>. <b>21</b> (4): <span class="nowrap">1697–</span>1698. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fic00134a093">10.1021/ic00134a093</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Inorg.+Chem.&rft.atitle=The+question+of+a+synergistic+metal-metal+interaction+leading+to+.pi.-back-bond+stabilization+in+dirhodium+tetrabutyrate+adducts&rft.volume=21&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1697-%3C%2Fspan%3E1698&rft.date=1982&rft_id=info%3Adoi%2F10.1021%2Fic00134a093&rft.au=Drago%2C+R.+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R._S.Vogel,_G._C.1992" class="citation journal cs1">Drago, R. S.; Vogel, G. C. (1992). "Interpretation of spectroscopic changes upon adduct formation and their use to determine electrostatic and covalent (E and C) parameters". <i>Journal of the American Chemical Society</i>. <b>114</b> (24): <span class="nowrap">9527–</span>9532. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja00050a035">10.1021/ja00050a035</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Chemical+Society&rft.atitle=Interpretation+of+spectroscopic+changes+upon+adduct+formation+and+their+use+to+determine+electrostatic+and+covalent+%28E+and+C%29+parameters&rft.volume=114&rft.issue=24&rft.pages=%3Cspan+class%3D%22nowrap%22%3E9527-%3C%2Fspan%3E9532&rft.date=1992&rft_id=info%3Adoi%2F10.1021%2Fja00050a035&rft.au=Drago%2C+R.+S.&rft.au=Vogel%2C+G.+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text">Drago, R. S. Applications of Electrostatic-Covalent Models in Chemistry, Surfside: Gainesville, FL, 1994.</span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDrago,_R.Wong,_N._S.1996" class="citation journal cs1">Drago, R.; Wong, N. S. (1996). "The Role of Electron-Density Transfer and Electronegativity in Understanding Chemical Reactivity and Bonding". <i>Journal of Chemical Education</i>. <b>73</b> (2): <span class="nowrap">123–</span>129. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1996JChEd..73..123D">1996JChEd..73..123D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fed073p123">10.1021/ed073p123</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Chemical+Education&rft.atitle=The+Role+of+Electron-Density+Transfer+and+Electronegativity+in+Understanding+Chemical+Reactivity+and+Bonding&rft.volume=73&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E123-%3C%2Fspan%3E129&rft.date=1996&rft_id=info%3Adoi%2F10.1021%2Fed073p123&rft_id=info%3Abibcode%2F1996JChEd..73..123D&rft.au=Drago%2C+R.&rft.au=Wong%2C+N.+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AECW+model" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) p 51 ISBN 978-0-470-74957-9</span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text">Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 ISBN 978-0-470-74957-9</span> </li> </ol></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=ECW_model&oldid=1246696870">https://en.wikipedia.org/w/index.php?title=ECW_model&oldid=1246696870</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Acid%E2%80%93base_chemistry" title="Category:Acid–base chemistry">Acid–base chemistry</a></li><li><a href="/wiki/Category:Inorganic_chemistry" title="Category:Inorganic chemistry">Inorganic chemistry</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Wikipedia_articles_needing_clarification_from_June_2021" title="Category:Wikipedia articles needing clarification from June 2021">Wikipedia articles needing clarification from June 2021</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 20 September 2024, at 14:30<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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