Malcolm J D'Souza, Jeremy Wirick, Jasbir Deol, Dennis N Kevill
{"title":"Classical tosylate/chloride leaving group approach supports a tetrahedral transition state for additions to trigonal carbon.","authors":"Malcolm J D'Souza, Jeremy Wirick, Jasbir Deol, Dennis N Kevill","doi":"","DOIUrl":null,"url":null,"abstract":"<p><p>The experimentally measured rates of solvolysis of 2-chloroethoxycarbonyl chloride (2-chloroethyl chloroformate, <b>3)</b>, 2-chloroethoxycarbonyl <i>p</i>-toluenesufonate <b>(5)</b>, and phenoxycarbonyl <i>p</i>-toluenesulfonate (<b>6</b>) were followed at 25.0 °C in various pure and binary aqueous-organic solvents with varying degrees of polarity. An analysis of the rate constants for <b>3, 5</b>, and <b>6</b>, was carried out using the two-term extended Grunwald-Winstein equation and comparisons are made to the previously published results for ethyl and phenyl chloroformate esters. The <i>k</i> <sub>OTS</sub>/<i>k</i> <sub>Cl</sub> rate ratios and the Grunwald-Winstein <i>l/m</i> ratios indicate the probability of a dominant bimolecular carbonyl-addition pathway in the more nucleophilic solvents. Nevertheless in <b>3</b> and <b>5</b>, in the strongly hydrogen-bonding 70% and 50% HFIP mixtures, a side-by-side ionization mechanism is favored.</p>","PeriodicalId":75259,"journal":{"name":"Trends in organic chemistry","volume":"19 ","pages":"1-11"},"PeriodicalIF":0.0000,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6366630/pdf/nihms-994812.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Trends in organic chemistry","FirstCategoryId":"1085","ListUrlMain":"","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
The experimentally measured rates of solvolysis of 2-chloroethoxycarbonyl chloride (2-chloroethyl chloroformate, 3), 2-chloroethoxycarbonyl p-toluenesufonate (5), and phenoxycarbonyl p-toluenesulfonate (6) were followed at 25.0 °C in various pure and binary aqueous-organic solvents with varying degrees of polarity. An analysis of the rate constants for 3, 5, and 6, was carried out using the two-term extended Grunwald-Winstein equation and comparisons are made to the previously published results for ethyl and phenyl chloroformate esters. The kOTS/kCl rate ratios and the Grunwald-Winstein l/m ratios indicate the probability of a dominant bimolecular carbonyl-addition pathway in the more nucleophilic solvents. Nevertheless in 3 and 5, in the strongly hydrogen-bonding 70% and 50% HFIP mixtures, a side-by-side ionization mechanism is favored.