Membranes hydrolytic decomposition

D. Hydrolytic Decomposition of Salts by a Membrane. — If pure water is put on one side, (2), of the membrane and the solution of NaR on the other, (1), the sodium ion has a tendency to go through to (2). This is possible only when the hydroxide ion also diffuses from (1) to (2). The solution in (1) becomes acid while that in (2) must be alkaline. The relations may be represented thus ... 

Several prodrugs of Hourouracil were obtained by acylation or carbamoylation of N-1 and/or N-3 atoms of the pyrimidine ring of 1. In particniar, an oral drug Carmofur (2) which is 1-hexylcarbamoyl derivative of 1 was launched in Japan in 1981 and later - in other countries [35], The carbamate moiety in 2 decomposes gradually in neutral water or in basic conditions, but it is strongly resistant to acidic hydrolysis and hence can survive acid in the stomach. The 1-hexylcarbamoyl moiety also facilitates the rapid uptake of 2 through the cell membrane [36]. The metabolic activation of Carmofur involves oxidation and scission of the side-chain with slow release of 1 [37]. Two main routes of the side chain transformation are (o-oxidation and ((o-l)-oxidation metabolites 40-43 were detected after adnunis-tration of Carmofur (Fig. 3) [38]. Non-enzymatic hydrolytic decomposition of 2 and its metabolites also contributes to release of 1. 

Under heated or hydrothermal conditions, the possible degradation mechanism for AEMs has been discussed in the literatures. Hydrolytic stability of the AEMs is performed by treating the membrane in hot water for a specific period. Only a few reports are concerned with the hydrolytic stability so far. For Watanabe research gronps, they performed the hydrolytic stability test in hot water at 80 C for 500 h the chemical structures before and after the hydrothermal test were analyzed by the use of H NMR spectra. A long-term hydrothermal test was also performed for 5000 h, and the ionic conductivity was used to assess the stability. According to their results, the major degradation mode of the AEM (based on quaternary PES) under the hydrothermal condition is most likely to be the elimination of a tertiary amine to form benzyl alcohol and its further decomposition via dehydration. ... 

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