The Phenolysis of Tetrahydrolinalyl and 2-Octyl Systems. The Rates, Steric Courses, and Product Distributions

Abstract

Abstract As tertiary and secondary systems with optical activity, tetrahydrolinalyl (methylethylisohexylcarbinyl) chloride or p-nitrobenzoate and 2-octyl p-toluenesulfonate have been selected, and their titrimetric and polarimetric rate constants (kt and kp) for SN1 phenolyses have been measured in the presence of triethylamine (or sodium phenoxide) in 50 wt% phenol–benzene. At higher amine (or phenoxide) concentrations, the kt and kp coincide with each other for tetrahydrolinalyl chloride (at 25.0°C) or p-nitrobenzoate (at 100.0°C), and also for 2-octyl tosylate (at 75.0°C), exhibiting the typical features of the nN1 solvolysis rate constant. In the absence of the amine (or sodium phenoxide), the kt diminishes to show a gap between the kp and the kt, indicating the occurrence of an ion-pair return in the phenolysis for both systems. Under the same reaction conditions as those of the rate measurement, tetrahydrolinalyl chloride and p-nitrobenzoate yield the phenyl ether, with a predominant racemization accompanied by some net inversion of the configuration, whereas 2-octyl tosylate gives 2-octyl phenyl ether, o-, and p-2-octylphenols, with a net inversion of the configuration accompanied by a slight racemization. These steric results indicate that phenol can be considered as a typical solvolytic solvent. The product distributions have been assessed for the reactions of 2-octyl chloride (200°C) and of tetrahydrolinalyl chloride (25.0°C) with the molecule of phenol under the SN1 phenolysis conditions, by extrapolating the product composition curves to a zero concentration of the phenoxide. For both systems, the phenol molecule is predominantly O-alkylated (74 and 99% respectively), accompanied by minor amounts of C-alkylation. In contrast to the phenol reaction, the phenoxide ion undergoes more C-alkylation (42 and 50% respectively).