Due to their synthetic utility, there is an increasing interest in ROCOX substrates. In medicinal chemistry, ROCOX compounds are common pharmaceutical reagents in the preparation of peptides, especially as blocking reagents for the protection of free amino or carboxyl groups. For binary solvent mixtures, the two-term Grunwald-Winstein equation is a linear free energy relationship (LFER) between the specific rates of solvolysis of a substrate in a given solvent and the corresponding scales of solvent nucleophilicity (NT) and ionizing power (YCl). Multiple regression analysis provides sensitivities l and m to NT and YCl respectively, and the l and m values serve as useful indicators for the determination of the mechanism of reaction. However, in multi-parameter equations, to avoid multicollinearity, it is important to analyze the solvolyses in solvents of widely ranging nucleophilicity and ionizing power values. In this project, we analyze the experimental data for six ROCOX substrates that have either a chloride or a tosylate as the leaving group. In addition, we analyzed instances when R is an alkyl group or is an aryl substituent. For the six substrates studied, the l/m ratios for similar compounds studied were constant and were independent of the leaving group. Furthermore, for all six ROCOX substrates, the resultant l and m values also signaled the occurrence of a dominant addition-elimination process with a rate-determining addition-step.

Will a change in the leaving group affect the rate and/or the mechanism of ROCOX solvolytic reactions?

255th National Meeting (2018)

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