Brucine, color reaction

Brucine gives the well-known intense orange-red coloration with traces of nitric acid. This color reaction is improved if the alkaloid is first dissolved in some acetic acid. 

The sensitive color reactions for nitrates with brucine or diphenylamine are not applicable in the presence of nitrites which give similar reactions. Hydrazoic acid can be used to destroy the nitrite beforehand ... 

For amounts of potassium nitrate higher than o-i% the reaction is sharp and intense. A feeble coloration with brucine or a slightly colomed ring with ferrous sulphate should be neglected, since extracts may derive traces of mtnc anhydride from the water used m their preparation, such quantities, however, never amount to o-i% of the extract... 

Nitrate is reduced to nitrite (by cadmium reduction reaction), which is then determined by diazotization (pH = 2.0-2.5) with sulfanilamide and coupling N-( 1 -naphthyl)-1,2-ethylendiamine hydrochloride to form an intensely pink colored azo dye (540 nm) Brucine oxidation by nitrate ion in H2S04 at 100°C to form a yellow compound (cacoteline), which is measured at 410 nm... 

Brucine is oxidized by 5 V nitric acid (or chromic acid (159)) at 0-5° to a rose-colored solution from which a red bruciquinone (bis-desmethylbrucine, (C21H20O4N2), XCIII) can be isolated as its perchlorate. It is a typical quinone because it is reduced by sulfurous acid to a hydroquinone, bis-apomethylbrucine (diacetate formation brucine yields two moles of methyl chloride when heated with hydrochloric acid but bis-apomethylbrucine could not be isolated from the reaction mixture (191) ). No other alterations occur in the brucine molecule during these transformations since methylation (dimethyl sulfate) converts bis-apomethylbrucine to the quaternary salt of brucine. The hydroquinone has been oxidized, with... 

Contrary to the statement in Standard Methods (1), it has been found that high concentrations of chloride ion produce a decrease in brucine-nitrate color in the standard brucine technique. The modified technique only gives a constant response with chloride concentrations between 27 to 50 grams Cl"/liter. In our modification the effect of variable chloride concentrations is masked out by adding a large amount of sodium chloride to the reaction mixture before color development (Table III). 

---