NMR ANALYSIS OF THERMAL REACTIONS OF RESIN ACID OF ROSIN
A comparative 1И and 13C NMR analysis of the thermal reactions of two samples of rosin and the abietic acid isolated from it at temperatures of 190 and 220°C with open air was carried out. Rosin was produced at JSC "Lesokhimik" (Borisov, Belarus) in 2006 and 2018. Seven resin acids were present in the initial samples: abietic, dehydroabietic, isopimaric, neo-abietic, palusturic, pimaric and sandaracopy-maric. We found an additional four acids in abietic acid (82.9%), which was isolated: dehydroabietic, isopimaric, neo-abietic, and palusturic. It was found that heating rosin at 190°C leads to the reversible isomerization of resin acids of the abietanic skeleton with the establishment of a new ratio of their content. The content of pimaranic type acids remains practically unchanged. It is shown that oxidation and destruction under these conditions are insignificant. Heating a mixture with a high content of abietic acid leads to a noticeable expenditure of it with the formation of an additional amount of acids present in the mixture. Thermolysis of rosin and isolated abietic acid at 220°C changes the dynamics of the reactions, that leads to a noticeable destruction of the components of the mixture. The effective interaction with molecular oxygen leads to the formation of dehydroabietic acid, some new acids and ketones.