ISSN:
0959-8103
Keywords:
cobalt(II)phthalocyanine-tetrasodiumsulphonate
;
poly(quaternary ammonium)salt
;
oligomeric ionenes
;
thiol autoxidation
;
catalysis
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
In order to study the promoting effect of polycations on the cobalt(II)phthalocyanine-tetrasodiumsulphonate (CoPc(NaSO3)4)-catalysed autoxidation of thiols, it is imperative to know the molecular weight dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elecidate the mechanism of the promoting effect of 2,4-ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4-catalysed autoxidation of 2-mercaptoethanol, a series of monodisperse 2,4-ionene oligomers were prepared. Trimeric 2,4-ionenes, containing two quaternary ammonium groups separated by four methylene groups, showed a high co-catalytic activity, and active Co-aggregates were detected with visible light spectroscopy. The spectroscopic behaviour was in close agreement with that of high molecular 2,4-ionene/CoPc(NaSO3)4 complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short the trimer acts as a simple salt in stablizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain lenght and reached a constant level of 50 at a 2,4-ionene nonamer. For the trimers and pentamers this ratio is affected by the type of end-group. All synthesized 2,4-ionene oligomers exhibited excellent co-catalytic properties at the optimum N+/Co ratio, with maximum turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer-free system. In the case of monodisperse 2,4-ionene pentamer with bromo end-groups, double Michaelis-Menten kinetics were observed, as also was exhibited by high molecular weight ionene.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pi.1994.210330109
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