Pyridine sorption, effect

Pyridine-bound resins were also prepared and successfully employed as polymer-supported phase transfer catalysts in bromide displacement from 1-bromoalkanes by salt phenoxide or naphthoxide, even though the controlling factor (diffusivity or preferential sorption) for the observed substrate selectivity effects was difficult to determined.[133]... 

Reduction of sugars into alditols is effected by treatment with sodium borohydride, and acetylation by treatment with acetic anhydride containing sulphuric acid (2%) at 80°C for 15 h [436] or for 4 h by refluxing with a mixture of acetic anhydride and pyridine (1 1) [437]. The excess of reducing agent is usually decomposed prior to the acylation by treatment with an acid. The boric acid so produced should be removed, as it forms a complex with alditols and retards the acylation. Polar stationary phases (e.g., Carbowax 20M), on which strong sorption and decomposition of the derivatives occur, are not very suitable for the GC separation of acetates. Carbowax 20M modified with terephthalic acid and XE-60 provides good results, but some derivatives do not separate. 

Waksmundzki et al. extensively examined the surface areas and microporosities of imprinted silica surfaces [44]. It was found that although the template itself had little effect on the total surface area, the sizes of the micropores were positively correlated to the size of the template. Subsequent studies on the sorption of template to silicas imprinted with pyridine [45-50], quinoline and acridine [45-47], and 2-picoline, 2,4-lutidine and 2,4,6-collidine [50], combined with thermodynamic studies on the heat of wetting of template or methanol/water sorption [47,51-53], led to the conclusion that these templates were adsorbed as multilayers to the silica. This observation supported the association mechanism hypothesis. The possibility of a footprint mechanism and an association mechanism coexisting in a concentration dependent fashion does not appear to have been considered. 

Surprisingly, in the case of CTO the admixture of a small amount of pyridine to the reaction mixture had no significant influence. Moreover, the increase in the pyridine amoimt leads to a decrease of the CTO conversion, maybe by blocking of sorption sites. A similar effect can also be seen when pyridine is added to a TO feed. The selectivity is only slightly increased. A significant improvement of the catalytic performance is obtained when pyridine is added... 

The effect of soil pH on the sorption of organic bases is well illustrated by observations with pyridine, quinoline, and acridine, three heterocyclic nitrogen compounds, using subsurface materials whose properties are listed in Table 3.1. The Freundlich K values and exponents are summarized for two subsoils in Table 3.10. 

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