If pine resin is heated to over 100°C, water and turpentine oil escape and a glassy mass remains after cooling, the rosin. The main component of rosin is abietic acid (C20H30O2) with various isomers such as dextropimaric acid and laevopimaric acid. The proportion of abietic acid in rosin is up to 90%. The aforementioned resin acids exist in a supercooled, amorphous state and tend to crystallize upon melting. Pure abietic acid is colorless and insoluble in water. Its solubility in organic solvents such as alcohols, acetone and ether, however, is good. Abietic acid can cause an allergy to rosin. Since rosin derivatives are also found in cosmetics, they can cause allergies in rare cases.
As the main component of rosin, it is the main reactant in all reactions of rosin with other reactants, such as with maleic anhydride and the subsequent reaction with polyalcohols to form synthetic resin polyesters.KRAEMER Wiki