Specific kinetic salt effects upon the solvolyses of ferf-butyl bromide, 1-and 2-methyl-exo-2-chloronorbornane, isobornyl chloride, and camphene hydrochloride have been examined in methanol, aqueous methanol, acetone, 1,2-dimethoxyethane, and methanol-1,2-dimethoxyethane. Anion effects are important but cation effects are small (for Li+, Na+, and Et,N+). The anion order is CIO,-> OTos-» NO.i-» Br-> Cl-» no salt > F-> OH-. Isotopic and azide trapping experiments show that carbonium ions or ion pairs can return in solvolyses of camphene hydrochloride and ieri-butyl chloride, but return is not large enough to explain the salt effects. This conclusion is supported by the observation of specific salt effects upon solvolyses of isobornyl chloride and l-methyl-e$o-2-chloronorbornane. Retention of configuration in the methanolysis of isobornyl chloride and camphene hydrochloride shows that methyl or hydride shifts do not occur during the lifetime of the carbonium ions. Experiments on isobornyl chloride in aqueous methanol and acetone show that chloride and perchlorate ions have little effect upon the activity coefficient of the substrate. The transition state effects appear to be related, at least in part, to solvent structure induced interactions between the carbonium-like transition state, especially with a large anion such as perchlorate.
Hydrolysis and methanolysis of bornyl and isobornyl chloride, and of camphene hydrochloride, in alkaline or neutral solution, give only camphene and camphene hydrate or methyl ether, which rearrange in acid to isoborneol or its methyl ether. In alkali the product composition is independent of the substrate, but the amount of elimination increases with increasing concentration of lyate ion, with increasing temperature, and on addition of 1 , 2-dimethoxyethane. Lyate ions retard reaction slightly, and camphene is not formed by an E2 reaction.The approximate rates of solvolysis, relative to that of bornyl chloride, are isobornyl chloride 1.5 x lo5 and camphene hydrochloride 3 x lo8.Water speeds reaction, and lJ2-dimethoxyethane retards it.THE bicyclic chlorides formed by reaction of hydrogen chloride with a-pinene and camphene provided the first example of the Wagner-Meerwein rearrangement. The exoisomers , isobornyl chloride (I) and camphene hydrochloride [exo-2,2,3-trimethylnorbornyl chloride (III)] , ionise much faster than the corresponding open-chain or monocyclic chlorides, but bornyl chloride (11) has a " normal" rate of i0nisation.l [The configurations of (1)-( 111) are that of (+)-~amphor.~]Me Me
tert.‐Butylbromid, 1‐ und 2‐Methyl‐2‐exo‐2‐chlor‐norbornan, Isobornylchlorid und Camphenhydrochlorid werden in Methanol, Wasser, Aceton, Glykoldimethyläther und ihren Mischungen der Solvolyse unterworfen; die kinetische Beein?ussung der Reaktion durch zugesetzte Salze wird untersucht.
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