English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The kinetics and mechanism of the oxidation of some N-substituted-p-phenylenediamines over ZnO supported with some transition metal sulfates were investigated at 25 °C. The rate of reaction decreased in the following order; N,N,N´,N´-tetramethyl-p-phenylenediamine, TMPPD &gt; N,N-diethyl-p-phenylenediamine, DEPPD &gt; N,N-di-methyl-p-phenylenediamine, DMPPD, due to the positive inductive effect of alkyl groups. For the oxidation of DEPPD, the rate of reaction was observed to have the order: Cu(II) &gt; Fe(III) &gt; Ni(II) &gt; Cr(III) &gt; Mn(II) &gt; Co(II). The initial rate of reaction was decreased with decreasing pH as a result of the protonation of the diamine nitrogen atoms. Also, it follows a first order dependence of the initial concentration of the diamine and attained a maximum at higher concentrations. Moreover, it increased with increasing amount of the oxidant. Greater amounts, however, reduced the rate of reaction as a result of the adsorption of the formed p-semiquinonediimine, S + , by the support. A mechanism is proposed which implies two consecutive electron transfer steps as well as a synproportionation reaction between the diamine and the totally oxidized p-quinonediimine, T.

Kinetics and Mechanism of the Heterogeneous Oxidation of N-Substituted-p-Phenylenediamines over Supported Zinc Oxide