Investigation of the catalyst in the cellulose–DMEU reaction. Part II. Physicochemical studies of the reaction

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Abstract
In a continuation of a previously reported investigation into the effect of the catalyst in the cotton cellulose–DMEU reaction, experiments were performed in which the four inorganic salt catalysts originally studied, MgCl2, Mg(NO3)2, ZnCl2, and Zn(NO3)2, were employed at the higher metal ion concentration of 0.1M, and CuCl2and CdCl2were employed at 0.03Mconcentration. Data from infrared absorption spectra of the treated cotton products were in agreement with those obtained at the 0.03Mcatalyst concentration, again indicating that the catalyst entered into the reaction, forming a coordination complex through the formation of nitrogen‐to‐metal bonds between the catalyst and the DMEU molecule. Similarly, it was again indicated that reaction with DMEU takes place preferentially at the primary alcohol group of the anhydroglucose unit. Analyses of IR data indicated a higher degree of crosslinking, and thus fewer terminal OH or NH groups at the 0.03Mcatalyst than at the 0.1Mcatalyst concentration. Further evidence of complex formation was obtained from infrared spectra of the product of the CdCl2–DMEU reaction carried out in the absence of cellulose. Supplemental physical data obtained on products of reactions catalyzed with CdCl2and CuCl2at the 0.03Mlevel, when compared with those obtained on products catalyzed with MgCl2and ZnCl2, supported the earlier hypothesis that chlorine damage during heating was dependent upon the ability of the metallic complex to act as a free‐radical trap. Additional support for the free‐radical mechanism was obtained when treated cloth subjected to chlorination and exposed to ultraviolet radiation suffered the same discoloring and degradative effect as cloth chlorinated and subsequently scorched according to the usual AATCC method. Reaction rates of the cellulose–DMEU reaction at 45, 55, and 65°C. with each of the four catalysts at the 0.03Mconcentration were determined by following changes both in nitrogen and formaldehyde content as well as in crease recovery properties. The reaction was found to be pseudo first order when followed to 2/3 completion, and the catalysts, when ranked according to greatest to least effect upon the reaction rates, followed the order: Zn(NO3)2> ZnCl2> MgCl2= Mg(NO3)2. Enthalpies, entropies, and free energies of activation have confirmed the earlier hypothesis that the metal ion enters into the reaction, forming a transition state complex.