Journal of the Chemical Society. Perkin transactions II p. 291 - 296 (1983)
Update date:2022-08-04
Topics:
Taylor, Roger
Rate coefficients for pyrolytic elimination of ethyl, isopropyl, and t-butyl carbonates, and of di-t-butyl carbonate have been measured over a 50 K range for each compound.The relative rates at 600 K are 1:29.6:2934:3526 and the rate spread for the primary, secondary, and tertiary compounds is inconsistent with that obtained from elimination of a range of other esters including alkyl phenyl carbonates.The least reactive compounds are found to be more reactive than predicted, probably owing to a combination of the greater Ei character of their transition states and the high nucleophilicity of the carbonyl group in dialkyl carbonates.Rate data for pyrolysis of S-ethyl, S-isopropyl, and S-t-butyl O-methyl carbonates give the relative rates at 600 K as 1:22:1074.The But:Pri rate ratio (49:1) is therefore greater than the Pri:Et ratio, as it is for all other related eliminations; this confirms that the literature results (which show the converse) are in error.The seemingly anomalous relative reactivities of thiolacetates and thiolcarbonates as compared with their oxygen-containing analogues is also shown to be consistent with the effect of variable polarity of the transition state in ester pyrolysis upon the importance of carbonyl group nucleophilicity, and this also accounts for the relative reactivities of thiol-, thion-, and dithio-acetates.Steric acceleration appears less important for carbonates than for acetates, since the rate for di-t-butyl carbonate (statistically corrected) is lower than for t-butyl methyl carbonate, whereas pivalates are more reactive than acetates.
View MoreContact:+ 86 512 52491118
Address:1 Fuyu Road, Haiyu TownChangshu, Jiangsu, China
Jiaozuo Zhongwen Trading Coporation Limited
Contact:+86 0391-3553810
Address:East Renmin Road
Contact:86-10-62983737; +86-10-51287608
Address:4/F Building C, 2 Shangdi Xinxi Road
Shandong Hongxiang Zinc Co., Ltd
Contact:086-0311-66187879
Address:DaWang developing zone
Shanghai Bojing Chemical Co., Ltd.
Contact:021-37122233
Address:6F Buildiing 11,No.388,Baifu Road,District Fengxian.Shanghai, China.
Doi:10.1021/ja991147x
(1999)Doi:10.1021/ja01362a017
(1931)Doi:10.1002/jccs.199900080
(1999)Doi:10.1055/s-1999-3573
(1999)Doi:10.1080/07328319908044769
(1999)Doi:10.1016/j.bmc.2017.07.034
(2017)
