Nucleophilic substitution at a trigonal carbon. Part 6. Substituent and bromide/chloride leaving group effects in the reactions of aromatic acyl chlorides with methanol in acetonitrile
Dn. Kevill et Wfk. Wang, Nucleophilic substitution at a trigonal carbon. Part 6. Substituent and bromide/chloride leaving group effects in the reactions of aromatic acyl chlorides with methanol in acetonitrile, J CHEM S P2, (12), 1998, pp. 2631-2637
Citations number
51
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
For the methanolyses in acetonitrile at 25.0 degrees C of benzoyl chloride
and eleven para- or meta-substituted derivatives, the kinetics of methyl es
ter formation have contributions both first-order and second-order in metha
nol. The Hammett plots for the overall second- and third-order processes ar
e curved and both plots can be analyzed in terms of the simultaneous operat
ion of two reaction channels. An addition-elimination process is favored by
electron-withdrawing substituents and a loose S(N)2 process by electron-su
pplying substituents. Comparisons of widely varying halogen leaving-group e
ffects suggest that the addition-elimination processes for solvolyses of ha
loformate esters and acyl halides have an identical addition step but they
then differ in the sequence of the two elimination steps.