ISSN:
0360-6376
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The kinetics of the dibutyltin diacetate (DBTDA)-catalyzed reaction of phenyl isocyanate with methanol in DMF and cyclohexane have been studied by monitoring the rate of change of the absorbance of the reaction mixture at 281.6 and 280.9 nm, respectively. Our results indicate that the mechanism of the reaction is independent of the nature of the (inert) solvent. The subsequent reaction steps are (i) complexation of methanol to DBTDA, (ii) dissociation of the complex into a proton and an anion of composition [(n-C4H9)2Sn(OCOCH3)2(OCH3)]-, (iii) insertion of the isocyanate into the tin - alkoxy bond (the rate-determining step), and (iv) methanolysis of the thus-formed urethane precursor with simultaneous regeneration of the anion. The rate of the catalyzed reaction increases on goin from coordinating to noncoordinating solvents. The following sequence in order of increasing rate constant was observed: DMF 〈 dibutyl ether 〈 cyclohexane. This is because in coordinating solvents, DBTDA and methanol, apart from forming a complex with each other, also form complexes with the solvent.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1981.170191203
