4-Bromophenacyl bromide reagent

Dissolve or suspend 0 - 5 g. of the acid in 5 ml. of water in a small conical flask, add a drop or two of phenolphthalein indicator, and then 4-5 per cent, sodium hydroxide solution until the acid is just neutrahsed. Add a few drops of very dilute hydrochloric acid so that the final solution is faintly acid (litmus).f Introduce 0-5 g. of p-bromophenacyl bromide (m.p. 109°) dissolved in 5 ml. of rectified (or methylated) spirit, and heat the mixture under reflux for 1 hour if the mixture is not homogeneous at the boiling point or a solid separates out, add just sufficient alcohol to produce homogeneity. [Di- and tri-basic acids require proportionately larger amounts of the reagent and longer refluxing periods.] Allow the solution to cool, filter the separated crystals at the pump, wash with a little alcohol and then with water. Recrystallise from dilute alcohol dissolve the solid in hot alcohol, add hot water until a turbidity just results, clear the latter with a few drops of alcohol, and allow to cool. Acetone may sometimes be employed for recrystallisation. 

The preparation of p-bromophenacyl bromide, which is a useful reagent for the characterisation of carboxylic acids (Section 9.6.15, p. 1261), is described in Expt 6.146. 

The most common fluorotags (fluorescent reagents) are dansyl chloride and o-phthalaldehyde (OPA). Chromotags include p-bromophenacyl bromide (PBPB) for derivatization of carboxylic acids (K-salts) with a crown ether catalyst, ninhydiin for primary amines forming complexes that have their adsorption maxima at about 570 nm, and dansyl chloride for primary and secondary... 

Sample preparation 1 mL Serum + 50 (xg IS + 100 (xL concentrated phosphoric acid + 2 mL dichloromethane, shake for 30 min, centrifuge at 2500 rpm for 10 min. Remove a 500 jxL aliquot of the organic layer and add it to 100 jxL reagent and 0.5 mg sodium bicarbonate, heat at 75° for 30 min, evaporate to 0.5 mL under a stream of nitrogen, make up to 1 mL with MeCN, iiyect an aliquot. (Reagent was 20 mM p-bromophenacyl bromide in MeCN containing 1 mM 18-crown-6, prepared by diluting Phenacyl-8 (Pierce) 5 times with MeCN.)... 

Sample preparation Dilute urine 10-fold with water. Mix 50 ixL plasma or diluted urine with 50 p,L 100 mM potassium dihydrogen phosphate, vortex, add 900 xL reagent, vortex, heat at 80° for 1 h, cool to room temperature, vortex, centrifuge at 1000 g, inject a 15 p.L aliquot of the supernatant. (Prepare the reagent by dissolving 66 mg 18-crown-6 and 1.39 g 4-bromophenacyl bromide in 100 mL MeCN.)... 

Proceed as for the p-nitrobenzyl ester, using p-bromophenacyl bromide or p-phenylphenacyl bromide in place of p-nitrobenzyl bromide. (The reagents are skin irritants.)... 

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