Phenolyses of 1-aryl-1-methylethyl p-nitrobenzoates and some simple alkyl systems: characteristic features of phenol as a solvolytic solvent

Abstract

In order to clarify the features of phenol as solvolytic solvent, phenolysis rates of the title compounds have been measured titrimetrically in pure phenol and in phenol–benzene as solvent at 50–125°. Specific rates in the presence of sodium phenoxide (apparent first-order rate constants) for the phenolysis of a series of α-methylated alkyl systems (RX; X = Br or OTs) change in the sequence R = Me > Et > Prⁱ Bu^t in phenol–benzene (1 : 1 w/w) at 125°. The first-order rate constants for the phenolysis of 1-aryl-1-methylethyl p-nitrobenzoates [ArC(Me)₂-OPNB; Ar =p-MeOC₆H₄, p-MeC₆H₄, Ph-, m-ClC₆H₄, and p-NO₂C₆H₄] obey a ρσ⁺ relationship with good precision (ρ–4.61; r 0.998 6) in pure phenol at 50°. The first-order phenolysis rates for a series of β-methylated primary alkyl tosylates (ROTs) increase in the order R = Me < Et ≃ Prⁿ < Buⁱ neo-C₅H₁₁ in pure phenol at 100 and 125°, indicating the high ionizing power of phenol, which is also deduced from the high Grunwald–Winstein Y value (1.77). The first-order rate constants for solvolyses of neopentyl tosylate in several hydroxylic solvents, including pure phenol, obey an mY relationship with fairly good precision (m+0.633: r 0.977 0). These results along with examples previously reported, demonstrate that phenol possesses features common to solvolytic solvents.