Thermochemistry of phenols: buttress effects in sterically hindered phenols

Thermochemical study of the ortho interactions in alkyl substituted anilines

“…Similar trends were already observed for the alkyl substituted phenols (5,7) and nitrobenzenes. (9) The meaningful stabilization (−10 kJ · mol −1 ) of 4-methyl-aniline seems to be doubtful, taking into consideration that no additional stabilization was detected in 2,4-di-methyl-aniline (table 6) in comparison with the 2-methyl-aniline. Also, no additional impact of the methyl substituent in the meta position of 2,5-di-methyl-aniline (table 6) is evident, again comparing with the 2-methyl-aniline.…”

“…The buttress effect (8) is the excess steric interactions of substituents in the case where there are three or more adjacent groups on three adjacent carbon atoms of the aromatic compound. The introduction of buttress corrections provides a substantial improvement of the predictive accuracy of the group-additivity methods.…”

“…(31) Meaningful buttress interactions of tert-butyl substituents with the OH-group have been detected in phenols. (8) We calculated the differences { H m (strain)} between the individual strains for each alkyl-aniline and the strain of the appropriate alkyl substituted benzenes (table 6, column 7). The values of { H m (strain)} were interpreted as the sum of the excess interactions of the alkyl substituents on the benzene ring with the NH 2 -group.…”

Thermochemistry of substituted benzenes: quantification of ortho-, para-, meta-, and buttress interactions in alkyl-substituted nitrobenzenes

“…The buttress effect (31) is the excess steric interaction of substituents in the case where there are three or more adjacent groups on three adjacent carbon atoms of the aromatic compound. The introduction of buttress corrections provides a substantial improvement of the predictive accuracy of the group-additivity methods.…”

“…(32) Meaningful buttress interactions of tert-butyl substituents with the OH-group have been detected in phenols. (31) We have calculated the differences { H m (strain)} between the individual strains for each alkylnitrobenzene and the strain of the appropriate alkyl substituted benzenes (table 6, column 6). The values of { H m (strain)} were interpreted as the sum of the excess interactions of the alkyl substituents on the benzene ring with the NO 2 -group.…”