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Infrared spectra of the acetyl derivatives of pectin. I. Potassium salts of the citrus pectic acid with different degrees of acetylation

M. P Filippov, O. Luknár, and R. Kohn

Institute of Chemistry, Moldavian Academy of Sciences, 277 028 Kishinev, USSR


Abstract:  Some acetyl derivatives of pectic acid with the degree of acetylation а = 0 — 1.81 and a very low degree of esterification of the carboxyl groups by methanol (e≤0.04) were prepared and characterized. The infrared spectra of the potassium salts of these substances obtained with KBr pellets were interpreted. The degree of acetylation of pectate could be easily determined by means of the relative absorbance dA expressed as a ratio of the absorbances A1/A2 determined in the region v(C = 0 ) of acetyl group (A1; 1738—1750 cm-1) and in the region vas(COO-) of dissociated carboxyl group (A2; 1615—1630 cm-1). The band vas(COO-) was used as an internal stan­ dard. A quadratic equation expressing the relationship between the degree of acetylation of pectate (a) and the relative absorbance (dA) at a known low degree of esterification of the carboxyl groups by methanol was derived.

Full paper in Portable Document Format: 322a211.pdf


Chemical Papers 32 (2) 211–217 (1978)

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