Experimental and molecular insights HDI trimerization catalyzed by potassium acetate/ benzyltrimethylammonium hydroxide

The HDI trimerization catalyzed by potassium acetate and benzyltrimethylammonium hydroxide was investigated experimentally. The composition and distribution of the products were analyzed by means of characterization. A Matlab R2002b-based kinetic model simulated monomer/trimer selectivity and product distribution over time, aligning well with experimental data. DFT calculations (M062X/def2-TZVP) explored reaction mechanisms, paths, and thermodynamics. Energy barriers for key steps were 68.2 kJ/mol (benzyl trimethyl ammonium hydroxide) and 75.3 kJ/mol (potassium acetate). Corresponding rate constants ( k ), calculated via KiSThelP using transition state theory, were 3.44 × 10 −10 and 5.17 × 10 −16 , respectively. Furthermore, electrostatic potential (ESP), independent gradient model (IGM), and electron localization function (ELF) analyses systematically revealed the catalytic mechanism of benzyltrimethylammonium hydroxide across electrostatic, bonding, and electronic structural levels. These combined experimental and theoretical approaches clarify the kinetics and mechanistic advantages of the quaternary ammonium catalyst in HDI trimer formation.