Abstract:

The geometry of abietic acid has been investigated by several theoretical methods including the Hartree-Fock and DFT-B3LYP level of ab initio theory. Its most stable structure is determined by the minimum energy. Comparing with the known experimental results， DFT-B3LYP which has the smallest error in three theoretical methods is the best one for analysis and predication of these systems. In the mean time， the relative energies of four resin acids in rosin were analysized by the B3LYP/6-31+G^** calculations. The calculation results predicted their stability and thermodynamic properties such as their values of Gibbs free energy， thermal enthalpies， thermal capacity and entropy. This research also shows that chemical calculations can be an important tool in scientific study. Accurate theoretical calculations can provide ways to obtain important chemical and physical information that cannot be easily obtained by experimental approaches. Clearly theoretical calculation gives a new method to investigate these systems.

Key words: abietic acid, rosin, stability, thermodynamic parameters