Computational Study of Catalytic Urethane Formation

Abstract

Polyurethanes (PUs) are widely used in different applications, and thus various synthetic procedures including one or more catalysts are applied to prepare them. For PU foams, the most important catalysts are nitrogen-containing compounds. Therefore, in this work, the catalytic effect of eight different nitrogen-containing catalysts on urethane formation will be examined. The reactions of phenyl isocyanate (PhNCO) and methanol without and in the presence of catalysts have been studied and discussed using the G3MP2BHandHLYP composite method. The solvent effects have also been considered by applying the SMD implicit solvent model. A general urethane formation mechanism has been proposed without and in the presence of the studied catalysts. The proton affinities (PA) were also examined. The barrier height of the reaction significantly decreased (∆E0 > 100 kJ/mol) in the presence of the studied catalysts, which proves the important effect they have on urethane formation. The achieved results can be applied in catalyst design and development in the near future.

A Theoretical Study on the Phosgenation of 2,4-Toluenediamine (2,4-TDA)

“…On one hand, there is an increasing request to understand industrial processes at the molecular level in order to use this information for the further process development. Many theoretical investigations are going on in the field of urethane industry, including phosgene production in presence of [NEt 3 Me]Cl/[NEt 3 Me][Cl 3 ] catalyst system [ 16 ], thermal decomposition of phosgene [ 17 ], the formation of other diamine intermediate (MDA), the phosgenation of MDA [ 15 ], the liquid structure of different isocyanates [ 18 , 19 ], urethane formation with an excess of isocyanate or alcohol [ 20 ], and in presence of catalysts [ 21 ], just to name a few. On the other hand, the chemical industries largely use the phosgenation of 2,4-TDA.…”

Experimental and Theoretical Study of Cyclic Amine Catalysed Urethane Formation

“…These reactions must be balanced for the proper quality of the final product and depends on the used catalysts [ 10 ]. Tertiary-amine-containing structures are usually used as catalysts in polyurethane reactions [ 11 ]. Therefore, much research aimed at studying their catalytic effect on polyurethane formation by using both theoretical and kinetic methods [ 11 , 12 , 13 ].…”

“…Tertiary-amine-containing structures are usually used as catalysts in polyurethane reactions [ 11 ]. Therefore, much research aimed at studying their catalytic effect on polyurethane formation by using both theoretical and kinetic methods [ 11 , 12 , 13 ]. Thus, the catalytic process and selectivity in many cases are well understood [ 14 ].…”

“…Computational studies have also been carried out to describe the catalytic process [ 16 , 17 ]. The catalytic effect of different amine catalysts on urethane formation has been studied using the BHandHLYP density functional theory (DFT) method in combination with the 6-31G(d) basis set and the G3MP2BHandHLYP composite method [ 11 , 12 ]. The results showed that by adding a catalyst to the system, the activation energy was significantly reduced, and urethane formation was promoted [ 11 ].…”

“…The catalytic effect of different amine catalysts on urethane formation has been studied using the BHandHLYP density functional theory (DFT) method in combination with the 6-31G(d) basis set and the G3MP2BHandHLYP composite method [ 11 , 12 ]. The results showed that by adding a catalyst to the system, the activation energy was significantly reduced, and urethane formation was promoted [ 11 ]. Despite all the efforts to understand polyurethane synthesis, there is still room for improvement in terms of the fine details of the reactions.…”