New Azo Derivatives of Ethanol Lignin: Synthesis, Structure, and Photosensitive Properties.

Water-soluble azo derivatives of lignin were synthesized by the azo coupling reaction using organosolv ethanol lignin and diazonium salts based on sulfanilic acid and p-nitroaniline. The structure of azo derivatives of lignin were studied by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was found that the azobenzene bonds formed in the azo coupling reaction of macromolecules impart the photosensitive properties to the synthesized polymers via cis-trans photoisomerization of the diazobenzene group. It was shown experimentally that the synthesized polymers exhibited good solubility both in the aqueous media in a wide (2-12) pH range and in DMSO and THF organic solvents, which opens up new prospects for their application.

Acceleration by Double Activation Catalysis and its Negation with Rising Temperature in Hydrolysis of Cellobiose with Phthalic and Hydrochloric Acids.

Double activation catalysis was experimentally observed in hydrolysis of cellobiose catalyzed simultaneously with phthalic and hydrochloric acids, confirming earlier theoretical prediction known from literature. Both acids can catalyze the reaction individually, and contribution of the double-activation pathway to the total reaction rate declines as temperature increases. In fact, above a certain temperature, the hydrolysis rate in presence of both acids becomes lower than the sum of the rates for the two acids acting individually. A kinetic model is proposed to explain this transition between double-activated catalysis and inhibition. The trend of declining contribution of cooperative catalytic pathway with rising temperature is theorized to be generally applicable for any reaction with a pathway involving simultaneous action of two catalysts when either of them can individually catalyze the reaction.