M. K. Rout

Retardation of Cerium(IV)-Initiated Polymerization of Acrylonitrile by Chalcone

Abstract The present investigation describes the kinetics and the mechanism of the inhibiting action of chalcone on the rate of Ce(IV)-initiated polymerization of acrylonitrile in the temperature range 30–40°C. The effect of monomer, metal ion, chalcone, perchloric acid, acetic acid, sodium sulfate, and manganese sulfate on the rate of polymerization has been studied. The most striking observation in the present investigation was the rate mechanism. The plot of [M]/Rp versus 1/[M] gave a negative intercept which appears to be a general phenomenon for all inhibiting substrates. The activation parameters were calculated, and a suitable reaction scheme is proposed.

The kinetics of retardation by phenol of the polymerization of acrylonitrile

Abstract The present communication discusses the kinetics of the retarding effect of phenol on the polymerization of acrylonitrile initiated by azobisisobutyronitrile (AIBN). The results are treated on the basis of the scheme proposed by Tudos et al.

Rate parameters for transfer reactions of some polymer radicals: in terms of Swain and Lupton's f and r and the unique positional weighting factors of Williams and Norrington

Abstract Rate parameters of the reaction of phenols, deuterated phenols and nitrobenzenes with polyvinylacetate radicals and of aromatic thiols with polymethylmethacrylate radicals have been correlated with Swain and Luptons substituent constants (Fk and Rk) and Williams and Norringtons unique positional weighting factors (fj and rj) by the following equation: P i = α i ƒ j F k + β i r j R k + e i + P 0 i where Pis are the rate parameters, P0i being that for a standard reference state. The correlations were found to be quite satisfactory. The sign and magnitude, and the ratio of the reaction dependent parameters αi and βi throw light on the nature of the transition state and the relative contributions of the mesomeric and inductive effects. The present studies also show that the mesomeric effect of meta-substituents is significantly greater than reported by earlier workers.

Retardation of Cerium(IV)-Initiated Polymerization of Acrylonitrile by Cinnamic Acid

Abstract The kinetics and the mechanism of retarding action of cinnamic acid on the Ce(IV)-initiated polymerization of acrylonitrile were studied in the temperature range 35–45°C. The rate of polymerization Rp was measured with respect to its dependence on time, monomer, metal ion, cinnamic acid, perchloric acid, acetic acid, sodium perchlorate, sodium sulfate, and manganese sulfate. The most significant observation was the rate mechanism. The process of polymerization was initiated by Ce(IV) alone and terminated essentially by the free radical produced by the interaction of Ce(IV) with cinnamic acid, which seems to be a general observation for all retarding substrates.

Ortho Effect and Additivity of Substituent Parameters in the Reaction between Phenols and Poly(vinyl Acetate) Radicals

Abstract The ortho effect and the additivity of substituent parameters in the reaction between phenols and poly(vinyl acetate) radicals have been investigated in the light of theories postulated by Swain and Lupton on substituent constants Fk and Rk and that of Williams and Norrington on the unique positional weighting factors fj and rj. The present correlation studies show that while Chartons theory that the ortho-substituent effect is primarily electrical is true for most of the substituents, some steric considerations have to be invoked while dealing with groups like o-tert-butyl. The additivity of fjFk and rjRk is much less satisfactory than that of Hammetts [sgrave] or Brown-Okamotos electrophilic [sgrave]+ substituent constants.

Substituent effects in the reaction between acetophenones and polyacrylonitrile radicals

The reactivity of substituted acetophenones towards polyacrylonitrile radical has been correlated with Swain and Luptons field and resonance parameters inclusive of the unique positional weighting factors suggested by Williams and Norrington. From the sign and magnitude of the reaction dependent regression constants, the transition state has been found to be essentially ‘non-polar’ in character.

Substituent Effects in the Kinetics of Polymerization of Acrylonitrile Retarded by Substituted Chalcones

Substituent effects in the kinetics of polymerization of acrylonitrile retarded by substituted chalcones are studied in terms of Hammett-type correlations with sigma-plus and also in terms of the field and resonance components of the substituents. With the modified sigma-plus values for halogen substituents, both the correlations are found to give excellent results. The significance of the values of the observed reaction constants and the relative merits of the two types of correlations are discussed, We have earlier reported [ 11 the kinetics of the Ce(IV)-initiated polymerization of acrylonitrile by chalcone, in which it was proposed that the polymerization of acrylonitrile by Ce(Iv) is retarded by a radical produced by the interaction of chalcone with Ce(IV). The following reaction scheme, which satisfactorily accounted for all the observed kinetic results, was proposed.

Substituent effects in the reaction between acetophenones and polymethyl methacrylate radicals

Abstract The substituent effects in the reaction between acetophenones and the polymethyl methacrylate radical have been correlated with Swain and Luptons Field (F) and Resonance (R) parameters including Williams and Norringtons unique positional weighting factors (SLWN) and also in terms of a conventional Hammett type equation with σ+. Excellent correlations have been obtained with both models. Attempts have also been made to ascertain the nature and characteristics of the transition state from the sign and magnitude of the reaction parameters.

Effect of Glycerol in the Polymerization of Methyl Methacrylate by Mn(III) Acetate

Abstract The kinetics of the mechanism of the polymerization of methyl methacrylate initiated by the glycerol/Mn(III) acetate redox system has been investigated in aqueous sulfuric acid medium in the temperature range of 40 to 50 °C. The effects of glycerol, methyl methacrylate, metal ion, acetic acid, and sulfuric acid on the rates of polymerization have been studied. One striking observation is that the increase in monomer concentration steadily decreases the rate of polymerization, contrary to what was observed in the case of acrylonitrile. On the basis of these observations, an appropriate kinetic scheme and rate expression have been developed.

Substituent effects in the reaction between benzaldehydes and polyacrylonitrile radicals

Abstract The effects of substituents on the reaction of benzaldehydes with polyacrylonitrile radicals have been studied in terms of the multiparameter equations based on Swain and Luptons Field and Resonance (F and R) components with the unique positional weighting factors f and r developed by Williams and Norrington. From the nature of the reaction constants, a polar transition state has been postulated.