Mechanistic investigations with positive halogens; kinetics of oxidation of thiosemicarbazide by chloramine-B, bromamine-B and dichloramine-B in acid medium.

Gowda, B.T.; Bhat, J. Ishwara

doi:10.1016/s0040-4020(01)86793-4

Cited by 13 publications

(3 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is evident from the comparison of kinetic data for TCH with those for its lower homologue, thiosemicarbazide (TSC) (table 5) (Gowda and Bhat 1987;Gowda and Rao 1988) that the dependence of rate on FH + ] is different in the two cases. If the terminal-NH2 groups were the attacking points one would expect deprotonation of -N + H3 groups in the pre-equ;.librium step.…”

Section: Comparisons and Conclusionmentioning

confidence: 99%

“…Hence a great deal of work remains to be done before one can start rationalising the role of metalthiosemicarbazide/thiocarbohydrazide/their hydrazones in the pharmacological field. In an effort to provide an insight into the mechanism of their activity in solution the kinetics of oxidation of thiosemicarbazide in the free state, and as its metal complex, by three N-halo aromatic sulphonamides have been studied in our laboratory (Gowda and Bhat 1987;Gowda ad Rao 1988). In continuation of the efforts in this direction, we report herein the kinetics of oxidation of thiocarbohydrazide in the free state and as its metal complex, and its hydrazone, bis-ethylidine thiocarbohydrazide by chloramine-T in aqueous perchloric acid medium, and by dichloramine-T in 1:1 (v/v) water-methanol medium, in the presence of perchloric acid.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Gowda

Sherigara

1989

Proc. Indian Acad. Sci. (Chem. Sci.)

Self Cite

View full text Add to dashboard Cite

Kinetics of oxidation of thiocarbohydrazide (TCH) in the free state and as its metal complex, and as a hydrazone by chloramine-T (CAT) in aqueous HC104 medium, and by dichloramine-T (DCT) in 1 : 1 (v/v) water-methanol medium in the presence of HC10 4 have been studied. Rates of oxidation of TCH in the free state and in metal complex by CAT were determined. The rate law for the oxidation of TCH at high [H + ] and for complex oxidations were identical to that for CAT oxidations. The conversion of TCH into its hydrazone changed the order in [H + ] from a positive to a negative value, probably signalling the change of reaction site. The rate law for oxidation under these conditions was determined. Addition of the reduced product of the oxidants had no effect on the rate of oxidations. Variation in ionic strength of the medium had little positive effect, while decrease in dielectric constant of the medium decreased the rate in both the oxidations. Oxidation processes generally follow a Michaelis-Menten type of mechanism. Constants of the rate limiting steps have been calculated at different temperatures and these constants have been used to calculate the activation parameters from the Arrhenius plots. The proposed mechanisms are supported by investigations with HOCI under identical reaction conditions. Metal complexation of the substrate decreased the reactivity, while conversion of TCH into its hydrazone changed the rate dependence on [H+].

show abstract

Section: Comparisons and Conclusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Gowda

Sherigara

1989

Proc. Indian Acad. Sci. (Chem. Sci.)

Self Cite

View full text Add to dashboard Cite

show abstract

“…Recently we have initiated some work (Gowda and Bhat 1987, 1988Gowda and Rao 1988;Gowda and Sherigara 1989;Gowda and Ramachandra 1989), to obtain some insight into the mechanism of their activity in solution. As part of these efforts, we have investigated the kinetics of oxidation of carbohydrazide by N-chloro and N-bromo p-toluenesulphonamides (chloramine-T and bromamine-T) in aqueous perchloric acid medium under varying conditions.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and mechanism of oxidation of carbohydrazide by chloramine-T and bromamine-T in aqueous perchloric acid medium

Gowda

Ramachandra

1990

Proc. Indian Acad. Sci. (Chem. Sci.)

View full text Add to dashboard Cite

Kinetics of oxidation of carbohydrazide by chloramine-T (CAT) and bromamine-T (BAT) have been studied in aqueous medium over a wide acid range, and are found to be [H + ] dependent. At low [H + ] (0-0005-4)q~75 tool dm-3), oxidation by both CAT and BAT shows first-order kinetics in [oxidant], fractional order in [substrate] and inverse fractional order in [H + 1. At [HCIO4] > 0-005 tool din-3, the rate dependence in [H +1 is zero and fractional order for CAT and BAT oxidations respectively and the kinetics in [oxidant1 and [sub6trate] are the same as before. Two pethways as well as Michaclis-Menten type nmdmnisms have been discussed to explain the observed kinetics and other effecm The rate controlling steps have been identified and the coefficients of these steps and the corresponding activation parameters are calculated. The rate constants are also predicted from the rate laws as [substrate] and [H § are varied. The predicted values are in reasonable agreement with the experimental rate constants.

show abstract

Kinetic and mechanism of oxidation of thiocarbohydrazide and its metal complex by acid bromate in aqueous and partial aqueous media

1993

View full text Add to dashboard Cite

The kinetics of oxidation of thiocarbohydrazide in the free and zinc(II)‐bound states by acid bromate have been studied in aqueous and water‐acetic acid (1:1, V/V) media under varying conditions, both in the absence and presence of added bromide ion. The rates of oxidations show first order kinetics in [bromate] in all the cases, but exhibit different kinetic behaviour in [substrate] and [H+]. Oxidation of TCH in aqueous medium shows zero order in [TCH] and nearly second order in [H+], while oxidation in aqueous acetic acid shows two ranges in [H+]. The rate shows first and fractional order kinetics in [TCH] in the first and second acid ranges. Kinetics observed in the presence of Br− are similar to those observed for oxidation of TCH in second acid range. In addition, the reaction shows fractional order in [Br−]. Oxidation of TCH in Zn(II)‐bound state exhibits first order kinetics in [substrate] and second order in [H+]. Increase in ionic strength of the medium decreases the rate in all the cases. Increase in acetic acid composition of the solvent increases the rate. Mechanisms consistent with the observed results have been considered and the rate laws deduced. The rate limiting steps have been identified and the coefficients of these steps have been calculated at different temperatures. The related activation parameters have also been computed. The validity of the deduced rate laws has also been tested by recalculating the rate constants from them as [TCH] and [H+] are varied.

show abstract

Mechanistic investigations with positive halogens; kinetics of oxidation of thiosemicarbazide by chloramine-B, bromamine-B and dichloramine-B in acid medium.

Cited by 13 publications

References 14 publications

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Kinetics and mechanism of oxidation of carbohydrazide by chloramine-T and bromamine-T in aqueous perchloric acid medium

Kinetic and mechanism of oxidation of thiocarbohydrazide and its metal complex by acid bromate in aqueous and partial aqueous media

Contact Info

Product

Resources

About