Effect of catalysts on the reaction of an aliphatic isocyanate and water

Abstract

The kinetics of the reaction of aliphatic isocyanate with water were investigated with hexyl isocyanate as a model compound. The kinetic study was carried out with a titration method to determine the concentration of the isocyanate group as a function of time. Gas chromatography was used to augment the kinetic data obtained from the titration method. The effects of an organic acid [p-toluene sulfonic acid monohydrate (p-TSA)], a tertiary amine {diazabicyclo[2.2.2]octane (DABCO)}, and an organotin compound [dibutyltin dilaurate (DBTDL)] on the reaction were investigated for the conversion of isocyanate to a urea. Under the reaction conditions in this study, urea was the only product observed. The rate constants indicated that p-TSA had low catalytic activity, DABCO had intermediate catalytic activity, and DBTDL had high catalytic activity. A reaction mechanism was proposed for each of the catalysts.

Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: A study of chemical pathways

“…Though it has never been used with wood, DBTDL was reported to catalyse the reaction of isocyanates with alcohols (Subrayan et al 2000;Gupta and Adhikari 2001;Ni et al 2002) and was recently applied to the synthesis of cellulose carbamates, in mild conditions (Mormann and Michel 2002). Results in Table 1 show that a significant WPG can be obtained without a catalyst, but the reaction rate was improved up to three times when Py or DBTDL were added.…”

Modeling reaction kinetics of rigid polyurethane foaming process

“…5 Therefore, an increase in the understanding and ability to predict the polyurethane foaming process and resulting properties can enable superior formulation design, expedite development of new formulations, and enhance materials properties. 2 Others have worked on modeling to predict material properties in order to reduce time on performance tests. [6][7][8][9] Ni has performed kinetic study with a titration method to determine the concentration of the isocyanate group as a function of time and estimated the rate constants of the reaction of isocyanate with water by linear regression.…”

Bulk Gold-Catalyzed Reactions of Isocyanides, Amines, and Amine N-Oxides

“…The reaction of isocyanates with water is well-known. 25,26 Mechanistic studies suggest that it proceeds by initial attack of water on the isocyanate to form a carbamic acid intermediate, which undergoes decarboxylation to generate the primary amine and carbon dioxide (eq 12). The isocyanate then reacts readily with the amine to give the urea (eq 13).…”

“…The isocyanate then reacts readily with the amine to give the urea (eq 13). 25,26 The reaction of isocyanates with water is known to be catalyzed by tertiary amines and other compounds. 26 Since a tertiary amine is produced in our reactions (eq 6), it is plausible that it catalyzes this reaction, with even small amounts of water.…”