A bulk oil oxidation test has been used to investigate the pro-and antioxidant effects of iron and copper and also the effects of basic dispersants and detergents, zinc dithiophosphates, and other antioxidants. Lube oil stability is strongly influenced by the particular combinations and concentrations of transition metal or lube additive used. Zinc dithiophosphates, on their own, strongly inhibit iron-catalyzed oxidations, but their activity is greatly reduced in the presence of basic additives. Under certain conditions, soluble copper, even at very low concentrations, is a far more potent antioxidant than conventional aromatic amines or phenols. Proposed actions of copper as a radical scavenger and zinc dithiophosphates as

Certain differences in properties of phenyl, as compared with alkyl, esters containing boron have been observed. Whereas trialkyl borates (except trimethyl borate) show little tendency to form complexes with tertiary bases, triphenyl borate forms 1 : 1 addition compounds with pyridine, quinoline, and monoethylamine ; ability of triphenyl borate to co-ordinate with diethylamine, triethylamine, and tri-n-butylamine decreased in that order. Triphenyl borate and the phenoxyboron chlorides were obtained by interaction in appropriate proportions of boron trichloride with phenol. The phecoxyboron chlorides disproportionate reversibly, and form relatively stable co-ordination complexes with pyridine. Distillation of of tert.-butyl alcohol with triphenyl borate afforded isobutylene and diisobutylene. No interaction between boron trichloride and diphenyl ether was observed.

A number of triaryl borates have been prepared by interaction of boron trichloride and the phenol or naphthol, and steric and polar factors concerning their amine addition compounds are discussed. Ammonia forms 3 : 1 and 2 : 1 complexes respectively with tris-2 : 4 : 6-trichlorophenyl and triphenyl borate. Whereas P-nitrophenyl, o-tolyl, and o-chlorophenyl dichloroboronite are unstable, o-nitrophenyl dichloroboronite is by cornparison remarkably stable, a property ascribed to internal co-ordination ; but all form stable pyridine complexes. There is evidence of isolation of the mixed borate, ethyl di-o-nitrophenyl borate, which with pyridine gives triethyl borate, and the pyridine complex of the triaryl borate.TRIARYL BORATES have previously been obtained by heating a mixture of a phenol and boron trichloride (in a sealed tube),l boric acid,293 boric oxide,* or boron acetate.sv6 A number of triaryl borates (Table 1) have now been prepared by the addition of a solution of the phenol (3 mols.) in methylene dichloride to boron trichloride (1 mol.) at -70". Advantages of this procedure are that nearly quantitative yields are obtained, the only other product is gaseous hydrogen chloride, which together with the low-boiling solvent can readily be removed, the reaction is quick and easily controlled at low temperatures, and functional groups may be present.

No abstract

A natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert‐butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress–strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75°C., the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.