P-31 NMR-SPECTROSCOPY IN WOOD CHEMISTRY .6. SOLID STATE P-31 NMR OF TRIMETHYL PHOSPHITE DERIVATIVES OF CHROMOPHORES AND CARBOXYLIC ACIDS PRESENT IN MECHANICAL PULPS - A METHOD FOR THE QUANTITATIVE DETERMINATION OF ORTHO-QUINONES

The presence of carboxylic acids in trimethyl phosphite derivatized mechanical pulps significantly affects the signal intensity of the solid state P-31 NMR spectra. These signals attributed to trimethyl phosphite-carboxylic acid adducts appear at about the same chemical shift as those of ol-tho-quinone and coniferaldehyde adducts. The absorption intensity attributed to these adducts is highly dependent on the degree of ionization of the acid group. The formation of trimethyl phosphite adducts with carboxylic acid groups in pulp can be prevented by complete neutralization. Therefore, the signals in the solid slate P-31 NMR spectra of mechanical pulps treated with trimethyl phosphite gave an ortho-quinone group content in black spruce mechanical pulp of 0.7 per 100 C-9 units, in agreement with previously estimated figures using independent methods.