Structural effects in solvolytic reactions. XXVI. A critical study of the effect of solvent on the exo:endo rate ratio in the solvolysis of 2-norbornyl derivatives. Evidence that the exo:endo rate ratio is not the result of K/sub. delta. //K/sub s/ processes

Journal Article · Wed May 10 00:00:00 EDT 1978 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00478a031· OSTI ID:6651484

Brown, H C; Ravindranathan, M; Chloupek, F J; Rothberg, I

The generally accepted position that the exo:endo rate ratio in the solvolysis of 2-norbornyl derivatives is the result of a k/sub ..delta../ process for exo and a k/sub s/ process for endo was subjected to critical examination by investigating the exo:endo rate ratio as a function of solvent. These mesylates were synthesized, along with several representative derivatives (isopropyl, cyclopentyl, and cyclohexyl), and solvolyzed in pure water and in 60 percent aqueous acetone. The tosylates were solvolyzed in methanol and in formic acid. These data, as well as other data, including those for solvolysis in trifluoroacetic acid and hexafluoroisopropyl alcohol, were then subjected to critical examination. Over the entire range of solvents, log k/sub exo/ plots linearly against log k/sub endo/. This is not consistent with the usual interpretation that the solvolysis of the exo isomer involves a k/sub ..delta../ process, insensitive to the nucleophilicity of the solvent, whereas the solvolysis of the endo isomer involves a k/sub s/ process, sensitive to the nucleophilicity of the solvent. The solvolysis of 2-adamantyl tosylate has been proposed as a representative k/sub c/ process. Both exo- and endo-norbornyl tosylates are nicely correlated with the rates of solvolysis of 2-adamantyl tosylates over the exceptionally wide range of solvents here examined. On the other hand, isopropyl, cyclopentyl, and cyclohexyl derivatives, postulated to involve k/sub s/ processes, are not so correlated. Clearly it is necessary to reconsider the previous interpretation of the solvolysis of endo-norbornyl derivatives as involving a k/sub s/ process and the exo:endo rate ratio as arising from the operation of k/sub ..delta..//k/sub s/ processes. The data are in better agreement with the solvolyses of both exo- and endo-norbornyl proceeding through processes that are essentially k/sub c/.

• Research Organization: Purdue Univ., West Lafayette, IN
• OSTI ID: 6651484
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:10; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ACETONE
ALCOHOLS
ALKENES
AQUEOUS SOLUTIONS
CARBOXYLIC ACIDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CYCLOALKENES
DECOMPOSITION
DISPERSIONS
FORMIC ACID
HYDROCARBONS
HYDROXY COMPOUNDS
KETONES
KINETICS
METHANOL
MIXTURES
MOLECULAR STRUCTURE
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
REACTION KINETICS
SOLUTIONS
SOLVOLYSIS