131. Solvolysis of some trimethylnorbornyl chlorides

Abstract

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

Heterolysis and the Pyrolysis of Alkyl Halides in the Gas Phase

“…•76 to yield camphene, tricyclene, and bornylene (which rapidly undergoes a retro-Diels-Alder process yielding trimethylcyclopentadiene). The rate enhancement, isobornyl: bornyl = 20:1 at 400°, is small compared with that observed in solvolysis (~1 05 at 25°), indicating that neighboring group assistance is energetically less favored in the gas phase than in solution.184* 217 Herndon, et a/.,88 reported that exobornyl chloride decomposes at 300°, slightly slower than does secbutyl chloride. Here again, neighboring group assistance appears somewhat unfavorable.…”

The mass spectra of some methyl norbornyl chlorides

“…For isobornyl and bornyl chloride the relative rate is 2, as compared with 10 for exo-and endo-norbornyl b r~m i d e .~ For solvolyses the relative reactivity of the exo-isomer is very much greater for isobornyl-bornyl chlorides as compared with the norbornyl compounds. 15 These differences in relative rates point out the weakness of these analogies between The results for these chlorides and a-fenchene are given in Table 5 * and Figs. 5 and 6.…”

“…The prcparations of bornyl and isobornyl chloride (VI) and (VII) and carnphene hydrochloride (VIII) have been describcd. 15 a-Fenchene hydrochloride (XI) was prepared frorn a-fenchene (XV) and ethereal HCI and from a-fcnchol (10 g) in pentane (100 mi) and PCI, at o". The infrared spectrum of both products were identical and they had an n.1n.r.…”