Issue 8, 1983

Kinetics and mechanism of the quaternization of poly(4-vinyl pyridine) with alkyl iodides

Abstract

The preparation of pure samples of poly(4-vinyl pyridine), P4VP, and poly(4-vinyl pyridine-co-styrene), P4VP-S, suitable for quantitative quaternization reactions is described. Reactivity ratios at 343 K are r1= 0.69 ± 0.01 and r2= 0.46 ± 0.10 (1 is 4VP, 2 is styrene).

Quaternization reactions of P4VP with ethyl, n-butyl and n-hexyl iodides gave extent, ξ, against time plots which were very well fitted using the neighbouring-group model. The parameters are k0, K=k1/k0 and L=k2/k0, where ki is the rate constant for reaction of a pyridyl groups with i already reacted neighbours. K and L pairs (±0.03) are: ethyl 0.96, 0.51; n-butyl 0.70, 0.30; n-hexyl 0.55, 0.27. The retardation compared with overall second-order behaviour, K=L= 1, increases with alkyl-group size. Quaternization of P4VP + n-butyl iodide in sulpholane, with and without 4-methyl-N-ethyl pyridinium iodide, showed that added salt had no effect on the kinetics. The neighbouring-group effect was absent from the quaternization of P4VP-S containing 0.2 mole fraction vinyl pyridine. The results of retardation are discussed in terms of a steric rather than an electrostatic mechanism, although the precise mechanism is not known. The results and conclusions are comparable with those found previously with alkyl and arylalkyl bromides.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans. 1, 1983,79, 1951-1958

Kinetics and mechanism of the quaternization of poly(4-vinyl pyridine) with alkyl iodides

E. A. Boucher and E. Khosravi-Babadi, J. Chem. Soc., Faraday Trans. 1, 1983, 79, 1951 DOI: 10.1039/F19837901951

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