13C Nuclear Magnetic Resonance Studies of Phenol‐Formaldehyde Resins 1 ‐ Model Compounds

High resolution 13C n.m.r. data are presented for a series of model compounds generated by the acid catalysed reaction of either phenol or cresol with formalin. The pure compounds prepared for this study allow unambiguous identification of features associated with ortho-ortho, ortho-para and para-para linked moieties, and hence allow analysis of the sequence structure in the typical resin. To aid assignment of the spectra a comparison is made between the predictions of the spectra using simple additivity relationships and the experimentally observed shifts. It is found that the differences between theory and experiment vary systematically with structure, and averaged correction factors are presented for various characteristic structures.