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 redox behaviour of N,N-dimethyl-p-phenylenediamine (PPD) and N,N-dimethyl-p-phenylenediamine · 2HCl (PPD · 2HCl) in acetonitrile was studied by means of cyclic voltammetry – both in the absence and in the presence of proton accepting pyridine. The oxidation occurs in two separate steps yielding first N,N-dimethyl-p-semiquinonediimine (SQDI + ) and subsequently N,N-dimethyl-p-quinonediimine (QDI 2+  or QDI + (H + )). In case of N,N-dimethyl-p-phenylenediamine the 1 st  oxidation step is fully reversible, while the 2 nd  oxidation step is slightly quasi-reversible. At 10°C the formal redox potentials of the PPD/SQDI +  and SQDI + /QDI 2+  redox couples are −0.200 ± 0.005 V and 0.380 ± 0.010 V ( versus  Fc/Fc + ), respectively. The synproportionation constant  K  syn  = [SQDI + ] 2 /[PPD][QDI 2+ ] is 2.1 × 10 10 . Adding pyridine to the reaction mixture leads to a shift of the 2 nd  anodic wave to less positive potentials. This shift is primarily due to proton transfer from QDI 2+  to pyridine to form QDI + , which overall renders the oxidation easier. The corresponding cathodic peak, on the other hand, disappears as the reduction of QDI +  necessitates a proton. The formal oxidation potential of the redox couple SQDI + /QDI + (H + ) is about 0.190 V and, therefore, the synproportionation constant  K  syn  = 1.7 × 10 6 . N,N-dimethyl-p-phenylenediamine · 2HCl lacks completely the 1 st  anodic peak. The position of the anodic peak is given by the direct oxidation of PPDH +  to QDI 2+ (H + ) and is similar to that of the SQDI + /QDI 2+  redox couple. Upon adding pyridine the 2 nd  anodic peak shifts notably to less positive potentials and the redox process attributable to the PPD/SQDI +  redox couple is seen. As pyridine influences the potential of the Ag pseudo-reference electrode a reference electrode based on the ferrocene/ferrocenium redox couple was used.

Cyclic Voltammetry of N,N-Dimethyl-p-Phenylenediamine and its HCl-Salt in Acetonitrile with Pyridine as Proton Acceptor