INVESTIGATION OF LIGNIN MODELS OF THE BIPHENYL TYPE BY X-RAY CRYSTALLOGRAPHY AND NMR-SPECTROSCOPY

Lignin models of the biphenyl type have been synthesized and crystal s tructures of two of them have been determined. The tetraacetate of is( hydroxymethyl)-3,3'-dimethoxy-2,2'-biphenyldiol crystallizes in space group P1BAR with a = 11.319(2), b = 12.232(6), c = 9.242(3) angstrom, alpha = 101.66(3)-degrees, beta = 108.14(2)-degrees, gamma = 79.08(2)- degrees and Z = 2. R = 0.036 (2720 observed [I > 3sigma(I)] reflection s). The acetate of 5,5'-di-tert-butyl-2',3,3'-trimethoxy-2-biphenylol crystallizes in space group P1BAR with a = 11.972(2), b = 21.621(3), c = 9.834(1) angstrom, alpha = 91.18(1)-degrees, beta = 113.13(1)-degre es, gamma = 98.42(1)-degrees, and Z = 4. R = 0.050 (8129 observed [I > 3sigma(I)] reflections). H-1 NMR and C-13 NMR data for the above-ment ioned compounds and a third model, the diacetate of is(1-hydroxyethyl) -2,2',3,3'-tetramethoxybiphenyl, are reported. Observed signal positio ns are compared with those calculated on the basis of crystal structur e data. The possibilities to obtain structural information about biphe nyl structures in lignins from NMR spectra are discussed.