Coulometric determination of aromatic nitro compounds with electrogenerated chromium(II)

Coulometric determination of several water-insoluble aromatic nitro compounds with electrogenerated chromium(II)

“…The coulometer, titration cell, and catholyte composition were as previously described (1). A 20-mA coulometric current, found to be satisfactory in earlier work.…”

“…This material yields the rapidly reducible CrBr(H,0),2+ species at a mercury cathode (3). A solution 0.1 M in CrBr(H,0),2' and 1.5 M in HCI was used as the catholyte in the coulometric cell (1) …”

“…Weigh the syringe before and after sample injection to determine the amount of sample delivered. Plot the readings against time of current generation and locate the end point by linear extrapolation (1). The amount of chromium(I1) to be generated beyond the end point depends on the compound being determined.…”

“…Electrochemically generated chromium(I1) at a mercury cathode has been applied to the determination of a number of aromatic nitro compounds in our laboratory (1). We became interested in determining whether this method could be applied to other water-insoluble nitro compounds, both to extend the analytical applicability of the system and to study the effect of various functional groups on the ease of reduction of the nitro group.…”

Titrations in nonaqueous solvents

“…Instead of bromine, manganese(III) or lead(IV) can be generated from the divalent salts for the same hydrazine determination (219). A number of substituted ferrocenes have been determined by oxidation with coulometrically generated copper(II) from copper(I) tetrafluoroborate in acetonitrile (152), and several water insoluble aromatic nitro compounds have been reduced with coulometrically generated chromium(II) after dissolution in acetonitrile or mixtures of water and acetonitrile or ethanol and injection into a catholyte of aqueous hydrochloric acid (5). Phenoxazones also are quantitatively reduced by electrogenerated titanium(III) in an ethanol-water mixture (283).…”