2002
DOI: 10.1021/jp0259723
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Ab Initio Studies of Thermal Syn-Elimination Reactions in Carbonates:  Effect of Structure on Reactivity

Abstract: Thermal elimination reactions in carbonates are investigated from a theoretical point of view with density functional theory methods to obtain insight into the reaction mechanism and structural factors that influence the kinetics. Carbonate systems are good model systems for the kinetics of thermal degradable polycarbonates. Special attention is given to the influence of para-substituents placed either at C R or C β . The results enable prediction of F values of the Hammett equation and confirm earlier experim… Show more

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Cited by 6 publications
(6 citation statements)
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“…level underestimate the influence of substitution effects, they do correctly predict that rearrangement rates are (i) more sensitive to aryl substitution at the a position on the carbonate alkyl chain, as opposed to the b position and (ii) show contrasting sensitivity to electron-withdrawing versus electron-donating substituents. Van Speybroeck et al, [51] who previously studied these reactions at the B3LYP/6-311G(d,p) level, noted these same trends and used them reasonably to conclude that the TS structure has more C-O bond breaking, with development of carbocationic character at the a position, than any corresponding bond making. Owing to the complexity of the substituted carbonates, Van Speybroeck et al developed initial geometries from PM3 calculations in order to be more efficient.…”
Section: Resultsmentioning
confidence: 79%
“…level underestimate the influence of substitution effects, they do correctly predict that rearrangement rates are (i) more sensitive to aryl substitution at the a position on the carbonate alkyl chain, as opposed to the b position and (ii) show contrasting sensitivity to electron-withdrawing versus electron-donating substituents. Van Speybroeck et al, [51] who previously studied these reactions at the B3LYP/6-311G(d,p) level, noted these same trends and used them reasonably to conclude that the TS structure has more C-O bond breaking, with development of carbocationic character at the a position, than any corresponding bond making. Owing to the complexity of the substituted carbonates, Van Speybroeck et al developed initial geometries from PM3 calculations in order to be more efficient.…”
Section: Resultsmentioning
confidence: 79%
“…Stabilization of the positive charge in the C α position affects acceleration of the reaction rate. The last step is a β-H-elimination or syn -elimination. , …”
Section: Resultsmentioning
confidence: 99%
“…The last step is a β-H-elimination or syn-elimination. 21,22 According to this mechanism, it is possible to tune the elimination temperature by changing the cation-stabilizing properties of the side chain. Based on this rationale, we set out to prepare derivatives changing the alkyl into an alkenyl (6h− 6j) or alkinyl (6e−6g) side chains, which form mesomerically stabilized cations and eventually lead to conjugated double bonds after elimination.…”
Section: Introductionmentioning
confidence: 99%
“…Several ab initio and density functional theory (DFT) studies have been performed to analyze the special characteristics of this reaction in different molecules. To carry out this task, analyses of the energies, atomic charges, kinetic parameters, and relative lengthening of the bonds have been done.…”
Section: Introductionmentioning
confidence: 99%