Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions.

Kyoung Ho Park,Dennis N Kevill,Jin Burm Kyong,Mi Hye Seong

doi:10.3390/ijms22147394

Abstract

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

Highlights

The chemistry of the acyl group and its various derivatives occupies an important place in organic and metabolic reactions [1,2]
Using the extended Grunwald–Winstein equation, we previously reported that the solvolysis of alkyl and phenyl chlorothioformates [15,16,17,18] in the more nucleophilic pure alcohols and aqueous solutions proceeds predominantly by an addition–elimination pathway (Scheme 1a), with an attack at the carbonyl carbon
The rate constants of solvolysis of 1 in all of the 20 solvents at 25.0 ◦C are reported in Table 1, together with the solvent nucleophlicity (NT) [21,22] and solvent ionizing power (YCl) [23,24,25] values

Summary

Introduction

The chemistry of the acyl group and its various derivatives occupies an important place in organic and metabolic reactions [1,2]. All of the reactions in 2 result in a loss of carbon dioxide to give the relatively sTable 1-adamantyl cation (1-Ad+Cl− ion pairs). The picture for the solvolysis–decomposition of 2 in hydroxylic solvents is expressed on the right side of Scheme 1, with pathways involving the rate-determining unimolecular reaction with a loss of carbon dioxide. Moss et al [10] studied product-determining intermediates on the solvolysis of 3-homoadamantyl chloroformate and 3-homoadamantyloxychlorocarbene in methanol. They demonstrated that the 3-HomoadOMe and 3-HomoadCl products are formed through an intermediate 3Homoad+Cl− ion pair after the loss of carbon dioxide or carbon monoxide occurs

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Discussion

Conclusion