Nuclear magnetic resonance spectroscopy acid anhydrides

Durette and Horton295(c) studied, by nuclear magnetic resonance spectroscopy, the anomeric equilibria at 27° of the aldopentopyranose tetraacetates in 1 1 acetic anhydride-acetic acid that was 0.1 M in perchloric acid. They found the following values for the ratios of the anomeric tetraacetates (/3la) at equilibrium, with the free energy A G° values for the J3 equilibrium (in parentheses) D-ribopyra-nose, 3.4 (—0.73 0.03) D-arabinopyranose, 5.4 (—1.01 0.03) D-xylopyranose, 0.23 (+0.89 0.03) and D-lyxopyranose, 0.20 (+ 0.98 0.05). 

Yan et al. [52] explored the use of IPN techniques to produce a composite vinyl-acrylic latex. The first-formed polymer was produced using VAc and divinyl benzene (DVB), while the second formed polymer constituted a BA/DVB copolymer. In both cases the DVB was added at 0.4 wt%. They compared this product with another product, a bidirectional interpenetrating netwodc (BIPN) in which VAc was again polymerized over the first IPN. They noted that the compatibility between the phases was more pronounced in the BIPN than in the IPN as determined using dynamic mechanical measurements and C nuclear magnetic resonance spectroscopy. The concept of polymer miscibility has also been used to produce composite latex particles and thus modify the pafamance properties of VAc latexes. Bott et al. [53] describe a process whereby they bloid VAc/ethylene (VAc/E) copolymers with copolymers of acrylic acid or maleic anhydride and determine windows of miscibility. Apparently an ethyl acrylate or BA copolymer with 10-25 wt% AA is compatible with a VAc/E copolymer of 5-30 wt% ethylene. The information obtained from this woik was then used to form blends of latex polymers by polymerizing suitable mixtures of monomers into preformed VAc/E copolymers. The products are said to be useful for coating adhesives and caulks. 

Synthesis. Functionalized monomers (and oligomers) of sebacic acid (SA-Me2) and 1,6 -bis(/ -carboxyphenoxy)hexane (CPH-Me2) were synthesized and subsequently photopolymerized as illustrated in Figure 1. First, the dicarboxylic acid was converted to an anhydride by heating at reflux in methacrylic anhydride for several hours. The dimethacrylated anhydride monomer was subsequently isolated and purified by dissolving in methylene chloride and precipitation with hexane. Infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis results indicated that both acid groups were converted to the anhydride, and the double bond of the methacrylate group was clearly evident. 

Amino groups have also been acetylated with acetic anhydride in dimethylacetamide. Diethylamine was added, and the excess amine was titrated potentiometrically. The sequence distribution of an aromatic polyamide terpolymer prepared under various reaction conditions was determined by nuclear magnetic resonance spectrometry. Infrared spectroscopy and mass spectrometry have been used to estimate the degree of conversion of polyimides, ie. the extent of polyamic acid ring closure. 

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