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cap alpha. -deuterium isotope effects in benzyl halides. 2. Reaction of nucleophiles with substituted benzyl bromides. Evidence for a change in transition-state structure with electron-donating substituents

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00541a014· OSTI ID:6934872
Rates and ..cap alpha..-D isotope effects have been determined for the following substrates and nucleophiles: p-methoxybenzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, OH/sup -/, S/sub 2/O/sub 3//sup 2 -/), benzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, OH/sup -/, S/sub 2/O/sub 3//sup 2 -/), and p-nitrobenzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, S/sub 2/O/sub 3//sup 2 -/). In nearly all cases the second-order rate constant for each nucleophile goes through a minimum for the unsubstituted compound while the ..cap alpha..-D isotope increases monotonically in the squence p-NO/sub 2/ > p-H > p-OCH/sub 3/. These results are consistent with an increasing looseness of the S/sub N/2 transition state as the substituent on the aromatic ring becomes more electron donating. 4 figures, 3 tables.
Research Organization:
Univ. of Maryland, Catonsville
OSTI ID:
6934872
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:21; ISSN JACSA
Country of Publication:
United States
Language:
English