Rate of enhancement of SN2 reactions in dipolar aprotic solvents. the importance of transition-state solvation

Paul Haberfield, Abraham Nudelman, Allen Bloom, Richard Romm, Henry Ginsberg, Peter Steinherz

Research output: Contribution to journalArticlepeer-review

Original languageEnglish
Pages (from-to)194-195
Number of pages2
JournalChemical Communications (London)
Issue number4
StatePublished - 1968
Externally publishedYes

Bibliographical note

Funding Information:
* . 0.00 - 3.7 f These two solvents have very similar dielectric constants (dimethylformamide ca. 37, methanol ca. 33) thus $ This was also observed by Parker and his co-workers, ref. 4, in the reaction of butyl halides and pyridine in meth- minimizing polarity differences and focussing upon the difference between aprotic and protic solvents. anol and dimethylformamide.CHEMICAL COMMUNICATIONS, 1968 195 activation is not paralleled by corresponding in the dipolar aprotic solvent and not by a solvent effects on the enthalpies of solution. Therefore, as shown in Table 3, the lower activation enthalpies This work was supported in part by the National for this reaction in the dipolar aprotic solvent are Science Foundation under its Undergraduate caused by greater solvation of the transition state (Received, December 28th, 1967; Corn. 1392.) Our calorimetric measurements (Table 2) possess an accuracy of about 2-4%. Yet changes in the heats of solution of several hundred percent would scarcely affect the validity of the above conclusion. C . A. Kingsbury, J . Org. Chem., 1964,29, 3262. For a review of other work see: A. J. Parker, Quart. Rev., 1962, 16, 163. D. J. Cram, B. Rickborn, C. A. Kingsbury, and P. Haberfield, J . Amer. Chem. SOL, 1961, 83, 5835. For a dis- discussion and other references see : D. J. Cram, “Fundamentals of Carbanion Chemistry”, Academic Press, New York, 1965. * E. M. Arnett, W. G. Bentrude, J. J. Burke, and P. McC. Duggleby, J . Amer. Chem. SOL, 1965,87, 1541. effect on the enthalpies of the reactants.§ Science Education Program 1963-1965. 5 It is important to note the very gross nature of this effect. B. 0. Coniglio, D. E. Giles, W. R. McDonald, and A. J. Parker, J . Chem. SOC. (I?), 1966, 152.

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