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Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV
Author(s) -
Fischer Walter,
Grob Cyril A.
Publication year - 1978
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19780610510
Subject(s) - chemistry , substituent , heterolysis , solvolysis , inductive effect , cationic polymerization , medicinal chemistry , polar , alkyl , reaction rate constant , electronic effect , stereochemistry , computational chemistry , photochemistry , organic chemistry , kinetics , catalysis , steric effects , hydrolysis , physics , quantum mechanics , astronomy
Three kinds of polar substitutent effects are observable in the solvolyses of 1‐R‐substituted 3‐bromoadamantanes (VI). This follows from the relationship between products, rate constants k in 80% ethanol, and the inductive substituent constants σ 1 qof the substituent R. Alkyl groups and electron‐attracting substituents at C (1) control the rate by their inductive effects alone, since log k correlates closely with σ 1 q . However, rates are higher than predicted on the basis of the respective σ 1 qvalues when conjugating (+ M )‐substituents or electrofugal groups are attached to C(1). These exalted substituent effects are attributed to CC‐hyperconjugative relay of positive charge from the cationic center at C(3) to the substituent at C(1). When the substituent is a strong electron donor ( e.g. O − and S − ), accelerated substitution gives way to heterolytic fragmentation, rates and products then being controlled by the frangomeric effect.