The Transmission of Polar Effects

Abstract

The transmission of polar effects by various groups is assessed by means of the reaction constants p or p". The results are critically discussed in terms of the various polar, steric, and solvent effects. Collclusions are drawn as to the importance of the inductive and direct field effects.

The synthesis and saponification kinetics of some 4′-substituted 4-phenoxyphenyl acetates

“…The shielding effect of the phenoxy bridge is substantial. The ratio p/po (po for substituted phenyl acetates, p for 4'-substituted phenoxyphenyl acetates) is 0.25 and agrees with that calculated from transmission coefficients for the transmission of polar effects through oxygen and phenylene links, 0.16 (8).…”

The transmission of polar effects. Part VIII. Esterification with diazodiphenylmethane and the ionization of ortho-substituted trans-cinnamic, phenoxyacetic, 3-phenylpropionic, cis- and trans-α-phenylcinnamic acids

“…The Hammett equation was used with para-o" values (19). These values are most applicable to the present insulated or partially insulated systems, and this scale was used in our previous analysis of metalpara-substitution in similar systems (2). A value of 0.530 is used for the ortho-nitro group to allow for steric deconjugation by the proximate link (18) and a o" value of 0.168 for the insulated ortho-or para-fluoro substituent (20).…”

“…However, if an inductive effect is mainly responsible, the ratio will remain the same. This is because the inductive effect decreases by a factor E for each intervening link (2,5).…”

“…However, if an inductive effect is mainly responsible, the ratio will remain the same. This is because the inductive effect decreases by a factor E for each intervening link (2,5).In this study, the reactivities of a series of ortho-substituted trans-cinnamic, phenoxyacetic, 3-phenylpropionic, cis-and traiw-ci-phenylcinnamic acids in their ionization and their reaction with diazodiphenylmethane in ethanol have been studied, together with the metalpara-substituted a-phenylcinnamic acids. The ortho-substituted -systems have been correlated by a Hammett-type equation and compared with the…”

Ionization constants of substituted benzoic acids in ethanol-water

“…Acco rdin g to Bowd en [21] (11) wh ere th e consta nts A a nd B res pec tively describ e th e usce ptibility of th e reac ti on to polar effec ts indepe nd e nt of and de pe nd e nt on th e medium. If A is negli gible co mp a red to B/E th e n p is in versely prop orti onal to E .…”