Equatorial 2a-, 4a-and 7P-amino-5a-cholestane are deaminated in acetic or aqueous acetic acid with predominant but not exclusive retention accompanied by some elimination. Axial 4pand 7a-amino-5a-cholestane are deaminated mainly with elimination, probably owing to the adjacent tertiary 5a-or 8P-hydrogen atom. 2P-Amino-5a-cholestane undergoes considerable elimination but also yields alcohols with predominant retention and acetates with predominant inversion. The ratio of epimeric alcohols formed differs considerably from the ratio of epimeric acetates produced in all these deaminations.The deamination process appears to be a complex reaction, greatly influenced by steric environment, which proceeds by a combination of SNi, S , 2 , and E2 mechanisms involving the diazonium ion, and by SN1 and E l mechanisms involving the intermediate solvated carbonium ion.
Electrodialysis is a widely used separation process for wastewater treatment, concentration of valuable products or production of organic acids. However, unwanted phenomena can occur during the operation of electrodialysis stacks such as internal leakage and/or external leak. In this study, a new simple tool is presented for testing materials suitable for use as spacers used in ED. This cell for testing leaks simulates ED stack and therefore allowing external leaks to be tested. Regarding tests results suitable materials for an ED scale-up can be chosen. Tests were done for three different pressures (1.5, 2 and 2.5 bar) and three different temperatures (25, 40 and 60 °C). To maintain the same conditions, the test cell was tightened by defined force in the range of 850 to 870 N. In the testing stack different combinations of membrane, and spacers were tested. It was found that with increasing temperature leaks decrease. Parameters that influence external leaks most are surface roughness, texture a hardness of ion-exchange membrane and spacer material.
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