The hydrogen bonding of the amide linkage has been studied by ab initio molecular orbital methods using STO-3G and 431G basis sets. Amide-amide (C=0• • H-N) hydrogen bonding is found to be stronger than amide-HsO bonding at the STO-3G level but not at the 431G level. The possibility of forming " " hydrogen bonds to the planar amide linkage is explored and it is found that only the carbonyl oxygen is a good "ir" hydrogen bond donor. Amide-2H20 complexes have been studied and the nonadditivity in hydrogen bonding found was qualitatively similar to that found in water polymers. The results found here are related to the experimental solution studies for amide association and further experiments are suggested to test the conclusions from our calcula-
The reactions of various commercially available epoxides with cotton cellulose in the presence of sodium hydroxide have been investigated at 25°, 50°, and 95° C. The effects of solvents and alkali content of the yarn steep on the epoxy add-on have been studied.
SynopsisReactions of various monoepoxides and diepoxides with diethylaminoethyl (DEAE) cellulose in the absence and presence of external catalysts have been studied. In the absence of additional catalysts, many epoxides which did not react with the unmodified cotton reacted with DEAE-cotton. Others, which reacted with unmodified cotton in the presence of external bases, imparted different properties when catalyzed by the builtin tertiary amino groups of DEAE-cotton. For example, epichlorohydrin reacted with DEAE-cotton to produce a fabric with excellent conditioned recovery, good wet recovery, and strong-base anion exchange properties. The same epoxide imparted only wet crease recovery to cotton when the reaction was catalyzed by external bases. Phenyl glycidyl ether and styrene oxide reacted with DEAE-cotton to produce a fabric with twentyfold improvement in resistance to flex abrasion. With 8% aqueous NaOH as an external catalyst, the DEAE-cotton displayed greater reactivity with all epoxides than did the unmodified fabric. DEAE-cotton-diepoxide reactions with added base catalyst generally resulted in a decrease in the conditioned recovery angle and an increase in the wet recovery angle. When Zn(BF& was used as an additional catalyst, again the D E h E fabrics displayed the greater reactivity toward the monoepoxides; but the unmodified cotton was more reactive toward the diepoxides than was the DEAE-cotton. The Zn(BF4)2-monoepoxide-treated DEAE fabrics had higher wet recovery angles but lower dry recovery angles than the corresponding epoxide-finished control cottons. Butrtdiene diepoxide was the only diepoxide investigated which imparted higher dry recovery angles to the DEAE-cotton than to the unmodified cotton control in the presence of Zn(BF4)2. Tertiary amino groups in DEAE-cottons act as an internal catalyst for the opening of the oxirane rings, direct the site for reaction in the absence of additional catalysts, and react with some epoxides to form quaternary nitrogen groups.
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