Acta Pharm. 54 (2004) 177-191

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Original research paper  

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


1Faculty of Pharmacy and Biochemistry, University of Zagreb, 10000 Zagreb, Croatia
2NMR Center, Rudjer Boskovic Institute, POB 180, 10002 Zagreb, Croatia
Received May 12, 2004      Accepted September 6, 2004

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.

Keywords: salicylic acid, 2,4- and 2,5-dihydroxy benzoic acids, methyl esters, amide derivatives, FT-IR, 1D and 2D homo- and heteronuclear 1H and 13C NMR