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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 28, Number 6
BKCSDE 28(6)
June 20, 2007 

Substituent Effects on the Gas-Phase Pyrolyses of 2-Substituted Ethyl N,N-Dialkylcarbamates: A Theoretical Study
Chang Kon Kim, Dong Jin Kim, Hui Zhang, Yih-huang Hsieh, Bon-Su Lee, Hai Whang Lee, Chan Kyung Kim*
Pyrolysis of carbamates, Hybrid density functional method, Variation of TS structures, Linear
The R- and Z-substituent effects for the gas-phase thermal decompositions of carbamates, R2NC(=O)- OCH2CH2Z, have been investigated theoretically at B3LYP level with 6-31G(d) and 6-31++G(d,p) basis sets. Both the Z- and R-substituent effects on reactivity (ΔH) were well consistent with experimental results, although the R-substituent effect was underestimated theoretically. No correlations were found between activation enthalpies and reaction enthalpies. The substituent effects on reactivity seemed to be complicated at a glance, but were understandable by concurrent electronic and steric factors. Variations of bond lengths at TS structures were well correlated with the Taft’s σ* values and the TS structures became tighter as the Zsubstituent became a stronger electron-acceptor (δσ* > 0). However the effects of R-substituents on the TS structures were much smaller when compared to those of Z-substituents.
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