THERMOCHEMICAL DECOMPOSITION OF CHOLIC-ACID AND ITS DERIVATIVES

The thermal decomposition reactions of cholic acid (1), methyl cholate (2), 3 alpha-acetoxy-7 alpha,12 alpha-dihydroxy-5 beta-methylcholanat e (3), 3 alpha,7 alpha-diacetoxy-12 alpha-hydroxy-5 beta-methylcholana te (4), 3 alpha,7 alpha-diacetoxy-12 alpha-oxo-5 beta-methylcholanate (5) and 3 alpha,7 alpha,12 alpha-triacetoxy-5 beta-methylcholanate (6) were studied by DTA and TGA. The thermal decomposition of cholic acid proceeds as a one stage process in the range 200-420 degrees C. The e sterification of the carboxylic group of cholic acid results in consid erable increase of the thermal stability of compound (2). The endother mic peaks at about 100 degrees C occurring only in compounds (1) and ( 2) can be attributed to desolvation and release of hygroscopically bou nd water. The thermal decomposition reactions of the dried compound (2 ) and compounds (3), (4) and (5) are found to proceed in two stages. D uring the first stage, the thermal degradation of (5) leads to the for mation of a completely deacetylated compound and two monodeacetylated compounds with the predominant product resulting from the elimination of the acetate group at C-3. Degradation of the carbon skeleton takes place during the second stage.