P-Bromophenacyl bromide

B) Phenacyl and p-Bromophenacyl esters. The sodium salt of an acid in aqueous-ethanolic solution will react with phenacyl bromide, CjHjCOCHgBr, and with p-bromophenacyl bromide, BrC,H4COCH2Br... 

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. 

Place a solution of 50 g. of p bromoacetophenone (Section IV,138) in 100 ml. of glacial acetic acid in a 500 ml. flask. Add very slowly (about 30 minutes) from a dropping funnel 40 g. (12-5 ml.) of bromine shake the mixture vigorously during the addition and keep the temperature below 20°. p-Bromophenacyl bromide commences to separate as needles after about half of the bromine has been introduced. When the addition is complete, cool the mixture in ice water, filter the crude product at the pump, and wash it with 50 per cent, alcohol imtil colourless (about 100 ml. are required). RecrystaUise from rectified (or methylated) spirit (ca. 400 ml.). The yield of pure p-bromophenac bromide (colourless needles, m.p. 109°) is 50 g. 

FLUORINECOMPOUNDS,ORGANIC - FLUORINATED AROMATIC COMPOUNDS] (Volll) p-Bromophenacyl bromide [99-73-0]... 

Method Cl (typical procedure) n-BuLi solution (1.6 M, 7.5 ml, 12.0 mmol) is added under Nj to a stirred solution of thiophene (1.12 g, 13.3 mmol) in dry THF (50 mL) at 0°C. After 50 min at room temperature, finely powdered tellurium (1.50 g, 11.8 mmol) is rapidly added under N2. After 30 min all the Te will have been consumed, and a solution of p-bromophenacyl bromide (1.6 g, 5.75 mmol) in THF (5 mL) is then added drop-wise over 10 min. The solution turns from light yellow to deep red as bis(2-thienyl) ditelluride is formed. After 30 min the solvent is evaporated and the residue partitioned in HjO/ether. The organic phase is dried (CaClj) and evaporated to give a red solid. Chromatography (Si02, CHjClj/hexane, 1 1) gives p-bromoacetophenone (0.82 g (72%) m.p. 49-50°C). 

Bromopentane, 279 p-Bromophenacyl bromide, 960, 961 p-Bromophenacyl esters, 362 o-Bromophenol, 666, 679 p-Bromophenol, 666, 679 Bromophenol blue, 989, 990... 

Acids, carboxylic acids 0-p-Nitrobenzyl-N,N -diisopropy lisourea (PNBDI) p-Bromophenacyl bromide (PBPB)... 

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 alkylation of (21) with phenacyl or p-bromophenacyl bromide to yield the 1,3-dithiolylium salts (171) offers a more special case. The methylene group of these salts can be deprotonated to form the unstable thiocarbonyl ylides (172) which collapse to the non-isolatable episulfides (175). Further reaction of (175) by loss of sulfur produces (174) whereas episulfide ring-opening and hydrogen shift followed by air oxidation leads to the disulfide (173) (80BCJ2281). 

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