Biofuel: The Next Generation of Green Energy

Theoretical Investigation of the Dehydration Mechanism of 1,3-Butanediol

The present study provides a comprehensive theoretical investigation into the dehydration mechanism of 1,3-butanediol (1,3-BDO) using density functional theory (DFT) methods — M06-2X and ωB97XD — alongside the ab initio composite method CBS-QB3.

Key thermochemical properties, including atomization enthalpy (AE), bond dissociation energy (BDE), ionization energy (IE), and electron affinity (EA), were computed for 1,3-BDO and all its dehydration products across multiple levels of theory.

The obtained results were benchmarked against previously reported theoretical and experimental data to validate the proposed mechanism. Thermodynamic analysis revealed that, although transition state TS2 exhibits a relatively low energy barrier, the pathway leading to 1,3-butadiene (1,3-BD) formation is the most favorable. In contrast, the formation of 1,2-butadiene (1,2-BD) is thermodynamically less probable.

Furthermore, BDE analysis showed that the inner alcoholic O–H bond is stronger than the terminal O–H bond by 6.4 kJ/mol, whereas the terminal O–H bond is weaker by 6.8 kJ/mol, reflecting the higher acidity of the terminal hydroxyl group in 1,3-BDO.