Urea‐formaldehyde resins. III. Constitutional characterization by 13C fourier transform NMR spectroscopy

Abstract 13C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of 13C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a 13C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated. Measurement of a 13C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a 13C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde.