The reactions of primary arylamines with aa-diphenyl-p-picrylhydrazyl in carbon tetrachloride have been found to obey the third-order law :Rate of disappearance of hydrazyl = k,[Hydra~yl]~[Aniline] A number of other amines and phenols gave a second-order reaction with the hydrazyl. Alcohols and t-butylamine did not, however, react a t an appreciable rate. The effects of substituents on the reaction with phenols are similar to their effects on reactions in which a carbonium ion is formed adjacent to a phenyl ring. Bulky groups ortho to the phenolic hydroxyl hinder the reaction. The reactions of 9-aminobenzonitrile, mand $-nitroaniline, $-aminobenzophenone, NN-dimethyl-pnitroaniline, and mand p-nitrophenol were greatly accelerated by light, and were then of first order with respect to aa-diphenyl-P-picrylhydrazyl and of zero order with respect to the amine or phenol. BRAUDE, BROOK, and LINSTEAD found that hydrogen transfer took place between the stable free radical aa-diphenyl-p-picrylhydrazyl and a number of quinols, catechols, hydroaromatic compounds, and aromatic amines. They measured the rates of reactions of the hydrazyl with some hydroaromatic compounds in dioxan, found that the reactions obeyed approximately the third-order law (rate = k,[Hydra~yl]~[Donor]), and showed that the energies of activation were between 20 and 35 kcal. per mole. Russell studied the reactions between aa-diphenyl-p-picrylhydrazyl and alkanethiols in benzene and found that the rates of disappearance of the hydrazyl could be expressed as 2k [Hydrazyl][Thiol]. At 6Q0, the values of k varied from 0-23 1. mole-1 min.-l for t-butanethiol to 4.56 for hexanel-thiol and the activation energy was in every case about 15 kcal. per mole. The products of the reactions of thiophenol, butanethiol, ammonia, hydrazine, hydroxylamine, methylamine, n-butylamine, isopropylamine, and diethylamine with aa-diphenyl-@-picrylhydrazyl were investigated and in every case high yields of aa-diphenyl-P-picrylhydrazine were obtained. The reactions between aa-diphenyl-P-picrylhydrazyl and some aromatic secondary amines have also been ~t u d i e d . ~. ~ Homolytic transfers of hydrogen atoms from donors to free radicals are of considerable interest in connexion with termination and transfer processes in chain reactions involving radicals. Autoxidations are important examples of such reactions. The propagation reactions are R* + 0, --t RO,.

MnO, produced Erom the MnSO, proved e f f d v e in alkaline solution. MnSO, was ineffective in acid solution. None of the other substances gave any evidence of assisting oxidation either in acid or alkaline solution. Series 111. Amorint of uatalyst.-Various amounts ofMnS0, were used and the times for reaching equilibrium compared. T o '50 ml. hl/Io Cr,(S04), were added 30 ml. 5~-sodium hydroxide and 20 ml. distilled water and the following amounts of ioyo MnSO, solution: 2 ml., I ml.,o.ag ml., 0 . xoml. 0.05 ml.ando.01 ml. There waslittle differencein oxidationrate between I ml. and 2 ml. but with quantities ofcatalyst less than this amount the rate of oxidation decreased rapidly. Also the 2 ml. were added in lots o f f ml. at intervals of one half hour. Table I1 indicates that I ml. of catalyst was the optimum. Figures are the mean of several oxidations and showed much variation. TABLE I1 Amount of camalyst Time for equilibrium : & Oxidation to I . 2 ml. in 4 lots 0.5 ml. at b hour intervals . 3 hours 6 5 % 7 0 8 2. -2 ml. 3 hours 65 %-70 I o 3. I ml. 3 hours 65 O/b-70% 4. 0.25 ml. 5 hours 35 %-4OO/ O 6. 0.05 ml. Indefinite negligible 7. 0.01 ml.