Acylation mechanisms in aprotic solvents. I. Methanolysis of p-nitrobenzoyl chloride in acetonitrile

Abstract

2-Azido-3-iodo-2-methylpentane (55) was prepared from 2methyl-2-pentene in 60% yield after purification on an alumina column: nmr (CC14) 4.11 (m, 1, Cff-I), 8.20 (m, 2), 8.48 (s, 3), 8.54 (s, 3), and 8.93 (t broad, 3).

Correlation of the rates of solvolysis of acetic p‐toluenesulfonic anhydride (acetyl p‐toluenesulfonate) and a comparison with acetyl halides

“…[45] For methanolyses of other acyl halides, proposed to be S N 2 in character, [24] acetyl chloride had a value [24] of 1.29, and values in the range of 1.38 to 1.48 were observed for propanoyl chloride, [25] cyclopentylacetyl chloride, [25] 3-phenylbutanoyl chloride, [25] and phenylacetyl chloride. [16] The k MeOH /k MeOD value of 0.99 AE 0.04 reported for methanolyses of 1 at À39.6 C (Table 1) is lower than the value for acetyl chloride at 0.0 C and is, therefore, even further removed from the values of greater than two which are observed when general-base catalysis by a second methanol molecule [46,47] is operating during substitution reactions at acyl halides which proceed through a tetrahedral intermediate. [24] The low value for the isotope effect is a strong indication that the methanolysis is not proceeding by an addition-elimination pathway and, presumably, an ionization reaction with assistance from nucleophilic solvation (Scheme 1) or a, closely related, S N 2 reaction with a loose transition state operates.…”

Concerted SN2 mechanism for the hydrolysis of acid chlorides: comparisons of reactivities calculated by the density functional theory with experimental data

“…Benzoyl chlorides with strong e‐w groups (e.g. 4‐NO 2 ) were suggested to react via Ad‐E pathway,13, 26, 62–65 with the general base catalyzed rate limiting attack of water and little or no bond breaking of the leaving group in the TS, even in highly aqueous media 13. Doubtful was, however, if there were an addition intermediate with significant long lifetime on the reaction path 26…”

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

“…Similarly, values of 2.17 ± 0.03 have been obtained for n -propyl chloroformate [ 57 ] and of 2.03 ± 0.01 for isobutyl chloroformate [ 58 ] methanolyses. The higher A-E values reflect, in part, the involvement of a second methanol [or methan (ol- d )] molecule as a general-base [ 37 , 59 ].…”

“…The situation can be simplified by use of MeOH and MeOD as the two solvents for comparison [ 36 ]. Addition-elimination (association-dissociation) substitution processes tend to involve a second nucleophilic molecule acting as a general-base [ 37 ] and this tends to raise the values for the k MeOH / k MeOD ratio above the values for either conventional bimolecular or unimolecular pathways.…”