The hydrolysis of pyrrolidine green and some derivatives. Part 2. The kinetics of the hydrolysis of some 3-substituted derivatives of pyrrolidine green

Abstract

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.

The effects of cyclic terminal groups in di- and tri-arylmethane dyes. Part 2.1 Steric and electronic effects in derivatives of Victoria Blue

“…27 Both Michler's ketone and its bis(diethylamino) analogue are commercially available, whilst benzophenones bearing cyclic terminal amino groups may be synthesised from 4,4Јdifluorobenzophenone or the corresponding dichloro compound via nucleophilic displacement. 1, 28 The ease with which a 4,4Ј-diaminobenzophenone is reduced to the corresponding alcohol was found to be dependent on the nature of the amino group. For example, Michler's ketone was reduced within a couple of hours by NaBH 4 in ethanol, whereas the bis(diethylamino) analogue needed 24 h and a much larger amount of borohydride to achieve reduction in refluxing propan-2-ol.…”

“…Increasing the length of the N-alkyl chains has a similar effect. 1, 28 Introduction of cyclic N-terminal groups also influences the spectral parameters and the λ max values of the symmetrical Violet and Green dyes 1 increase in the order R 2 = NMe 2 < morpholine ~pyrrolidine р NEt 2 < piperidine. 1 From a strictly electronic point of view, the ε max values of structurally symmetrical triarylmethane dyes should increase with increasing electron-donating ability of the terminal amino groups and so follow the trend exhibited by the λ max values.…”

The effects of cyclic terminal groups in di- and tri-arylmethane dyes. Part 3. Consequences of unsymmetrical substitution in Malachite Green

“…The perchlorates were purified by precipitation from acetone by the addition of diethyl ether and by crystallisation. The 4-aminobenzophenones were prepared from 4-fluorobenzophenone by nucleophilic substitution, refluxing the ketone with an excess of the cyclic amine in S,S-tetramethylene sulfone 12 (sulfolane) (Scheme 1).…”

Unusual Aminations with Tetramethylguanidine

“…The displacement of chloride or fluoride from electron deficient aromatic compounds on heating either in neat amine or with an amine in a co-solvent (e.g. DMSO, 10 DMF 11 or tetramethylene sulfone 12 ) has proved a fruitful route to aminobenzenes. 2 One function of particular interest to us was the guanidine unit.…”