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FT-IR and NMR spectroscopic studies of salicylic acid derivatives. II. Comparison of 2-hydroxy- and 2, 4- and 2, 5-dihydroxy derivatives

The 2, 4- and 2, 5-dihydroxybenzamides (8, 9) were synthesized from their corresponding methyl esters. The structures and the spectral properties of investigated salicylic acid (1), 2, 4- and 2, 5-dihydroxy benzoic acids (2, 3), their methyl esters (4-6) and amides (7-9) were analyzed by means of FT-IR and one- and two-dimensional homo- and heteronuclear 1H and 13C NMR spectroscopies. Comparison of FT-IR and NMR spectral data of investigated compounds showed that the spectral characteristics of 2, 4-dihydroxy benzoic acid derivatives are more similar to those of 2-hydroxy benzoic acid (salicylic acid) derivatives than to those of 2, 5-dihydroxy benzoic acid derivatives. The results suggest that the spatial orientation of amide protons in 2, 4-dihydroxy benzamide resembles more that in salicylamide than that in 2, 5-dihydroxy benzamide.

FT-IR ; NMR ; salicylic acid derivatives

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