The spectral shifts of the first absorption bands brought about by cyclic terminal groups in analogues of Michler's Hydrol Blue, Malachite Green, and Crystal Violet are determined mainly by inductive effects.Dye cations containing terminal pyrrolidino substituents are significantly more stable than those possessing piperidino groups as a result of differences in basicity brought about by a change in size of the saturated heterocyclic ring.

Apparent dipole moments in benzene of various p-substituted N-phenyl derivatives of pyrrolidine, piperidine, morpholine, and thiomorpholine and of some analogous NN-diethylanilines have been determined. Vector moments along the bisector of angle CH2NCH2 and also in the direction of the major axis of the aromatic ring have been calculated for the parent compounds. The order of magnitude of the latter is N-phenylpyrrolidine > NN-diethylaniline > N-phenylpiperidine > N-phenylmorpholine > N-phenylthiomorpholine. The nature of the heterocycle does not greatly affect the additional moment, p(add.), along the major axis of the aromatic ring, required to account for the moments of the p-substituted compounds. In each series of compounds, p(add.

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Rate constants have been measured for the reactions of hydroxide ion with Pyrrolidine Green and its 3-Me, 3-Br, 3-CF3, and 3-NO derivatives in aqueous solution. The substituents affect the rate of hydrolysis to an extent linearly rdated to the appropriate Hammett substituent constant. Thermodynamic parameters AH* and AS* have been determined for each dye. The existence of an isokinetic relationship has been established by analysis of Arrhenius plots and confirmed by other methods.Numerous ~h e m i c a l , ~. ~ biological,4*' and industrial applications of triphenylmethane dyes are known. The dyes show only poor to moderate fastness to washing and thus information on the hydrolysis of the dyes is important. In order to augment our knowledge of the protolytic and hydration equilibria and of the rates of hydrolysis of triphenylmethane dyes, we have extended our study of Pyrrolidine Green (I) to ascertain the influence of meta-substitution in the phenyl ring. The reactions of the dyes with water molecules and hydroxide ions over the pH range 10-1 1.5, within a temperature range 293.2-313.2 K at ionic strengths 0.005-4.5 mol dm-', are now reported.

Rate constants and the activation parameters AH* and AS* have been determined for the hydrolysis of Pyrrolidine Green over the pH range 10-1 1. The equilibria associated with the hydrolysis of the dye have been studied over the pH range 0-10 and a reaction scheme is proposed. Equilibrium studies have been extended in the pH range 6.8-7.8 and the thermodynamic parameters AH" and AS" have been obtained.During our studies of sterically hindered basic dyes, we have examined the spectral properties of a range of substituted derivatives of Brilliant Green * and studied their hydrolysis under basic conditions.2 The influence of substituents was such that it was considered of value to investigate the consequences of variation in the terminal basic groups. In this paper, the hydrolysis of Pyrrolidine Green, PG+ (11), over a wide pH range and over the temperature range 293.2-313.2 K is reported.