Kinetic Study on Solvolysis of 2‐Methylfuran‐3‐carbonyl Chloride in Binary Solvent Mixtures

Abstract

Rate constants for solvolysis of 2‐methylfuran‐3‐carbonyl chloride (1) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone, 2,2,2‐trifluoroethanol, and 1,1,1,3,3,3‐hexafluoro‐2‐propanol are reported. The 34 solvents give an extended Grunwald–Winstein correlation with l = 0.26 ± 0.05, m = 0.71 ± 0.04, and correlation coefficient R2 = 0.963. Activation parameters calculated from the rate constants measured at three different temperatures in five different solvents are presented. In the deuterated methanol, a solvent kinetic isotope effect of 1.15 was observed at 0°C. The kinetic features observed indicate that the reaction proceeds through an SN1 mechanism with a little SN2 character. The reactivity–selectivity principle is also followed in alcohol‐water mixtures.

Mechanistic Study of the Solvolysis of Piperidine‐1‐sulfonyl chloride in Binary Solvent Mixtures

“…20,21 The rate ratio in two solvents that have identical Y Cl values, i.e., the same degree of solvent assistance for bond breaking but different degrees of nucleophilicity, provides a measure of the minimum extent of nucleophilic solvent assistance. 12,24 The KSIE values of 1.28 and 1.34 observed for the solvolysis of 1 are consistent with the S N 1-S N 2 spectrum pathway. 18,22 The rate constants measured at three temperatures are reported in Table 2 together with the ΔH 6 ¼ and ΔS 6 ¼ values calculated from these data.…”

“…For the solvolyses of sulfonyl chloride derivatives, the sulfonyl sulfur reaction center has an N , N ‐dialkyl group, two double bonds to sulfur, and a pentacoordinate species arranged with chlorine atoms. The nucleophilic solvent attack and the electrophilic solvation of sulfonyl chloride derivatives can be described as shown in Scheme …”

“…12 The greater rate constants in 40% v/v EW than in 97% w/w TW provide evidence of the importance of nucleophilic solvent assistance, although the ionizing power is approximately equal in both solvents. 12,23 In deuterated methanol (MeOD) and deuterated water (D 2 O), KSIE values of 1.28 and 1.34 were observed. 20,21 The k 40EW /k 97TW ratio (=182) implies that the solvolyses of 1 in binary aqueous solvent mixtures proceed through channels associated with the S N 1-S N 2 spectrum mechanism rather than channels associated with the S N 2 and/or S A N (addition-elimination) pathway.…”

“…12 In recent years, mechanistic studies of nucleophilic displacement reactions at the tetra-coordinate sulfur center have included intensive experimental 8,9,13,14 and theoretical 15 efforts due to the wide range of applications of such reactions in the synthesis of sulfur drugs. The nucleophilic solvent attack and the electrophilic solvation of sulfonyl chloride derivatives can be described as shown in Scheme 1.…”

“…20,21 The k 40EW /k 97TW ratio (=182) implies that the solvolyses of 1 in binary aqueous solvent mixtures proceed through channels associated with the S N 1-S N 2 spectrum mechanism rather than channels associated with the S N 2 and/or S A N (addition-elimination) pathway. 12,24 The EGW equation (Eq. The ΔH 6 ¼ and ΔS 6 ¼ values are similar to those reported previously for bimolecular reactions, which proceed through a polar TS mechanism.…”