SOLVATION EFFECTS AND RELATIVE RATES III. SALT EFFECTS IN THE SOLVOLYSIS OF exo-NORBORNYL BROMIDE

Abstract

It is remarkable that all of the 1: 1 compouncls crystallize in the distorted NiAs (MnP) structure rather than the NiAs structure itself. In the palladium and platinum systems where one might anticipate the NiAs structure no 1: 1 compounds were obtained.The diphosphides, diarsenicles, and diantimonides of ruthenium and osinium have the marcasite structure, while the corresponding compouncls of palladium and platinum have the pyrite structure. The rather complicated diffraction patterns of RhAs, and IrAs? are most certainly related, ancl bear a distinct similarity to the pattern of CoAs, (8). A strong low-order reflection in the CoAs2 pattern is split in the RhAs, and IrAs2 patterns; this leacls us to doubt the orthoi-hombic cell we proposed earlier for CoAs2. These diarsenides may prove to be isostruct~iral with the rhodi~im ancl iriclium diphosphides mentioned by Rundqvist.Since the tripl~ospl~icles and triantimonicles of cobalt, rhodium, and iridium are known to have the cubic CoAs:, structure, it is not surprising that RhAs:! and 1 1 -A~~ have the same structure. The list of compouncls crystallizing in the sltutterudite systenl now stands a t 1 I , ancl insofar as binary pnicticles are concerned, call be considered to be complete. With the exception of NIP, ancl PclI's they are formed only by the cobalt family of transition metals. Bism~itl~ides with this structure have not been observed.'I'hese systems arc no\v being st~icliecl in some detail.

Specific salt effects upon the rates of SN1 solvolyses

“…The situation in the mixed solvents is therefore completely different from that in water. 14,15 We note also that cation effects are not large in these polar aqueous organic solvents, although in nonpolar solvents such as ether and acetic acid, a small high charge density cation such as lithium can electrophilically assist ionization.17 Presumably small cations are so strongly solvated in polar hydroxylic solvents that they are ineffective catalysts, and the importance of such catalysis should be reduced by solvation of the departing anion. One notable exception to this generalization is the observation that the rate of hydrolysis of p-chlorodiphenylmethyl chloride in 80% acetone-water increases linearly with concentration of lithium perchlorate but is little affected by tetrabutyl ammonium perchlorate,58 possibly because the latter salt is a weak electrolyte so that the perchlorate ion is less available to stabilize the carbonium ion (c/.…”

Solvolysis of cis-pinocarvyl p-bromobenzenesulfonate and related esters

“…Table XIIshows that the rate of alkaline methanolysis of cis-pinocarvyl brosylate in the presence of 0.5M lithium perchlorate is more than twice the rate of alkaline methanolysis in the absence of the ionic salt (134% increase in rate).Rate increases of 22 to 107% have been reported for the unimolecular solvolysis of various halides in the presence of O.1M lithium perchlorate(44)(45)(46).…”