Microstructure of polyisocyanates in solution by NMR studies of well defined oligomers

Abstract

Pentaethy biuret was synthesized by reacting two equivalents of diethyl amine with the carbamoyl chloride derivative of diethyl urea. The carbamoyl chloride was synthesized by treating the lithium salt of triethyl urea, formed by butyl lithium deprotonation in tetrahydrofuran at -78 °C, with one equivalent of phosgene. The hexaethyl triuret was synthesized by condensing the lithium salt of triethyl urea with one equivalent of the triethyl urea carbamoyl chloride derivative. Nuclear magnetic resonance (NMR) samples in freon21-d, CDFCL2 and tetrahydrofuran-d8 solvents were prepared using vacuum manifold techniques. 13C and 1H NMR spectra were acquired on a Varian INOVA-400 at various temperatures, and relaxation data were obtained on a Bruker AF300.