Phenylphenacyl bromide

Mesityl oxide (Section 111,79) (I) condenses with ethyl malonate in the presence of sodium ethoxide to give the sodium derivative of (II) this upon hydrolysis with aqueous potassium hydroxide, followed by acidification, gives the cyclic diketone 5 5-dimethyl-l 3-cycfohexanedione (III), of which the enoUc form is 5 5-dimethyldihydroresorcinol (IV)  

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Phenylphenacyl bromide [135-73-9] M 275.2, m 126°. Crystd (charcoal) from EtOH (15mL/g), or ethyl acetate/pet ether (b 90-100°). 

Cognate preparation. a-Bromo-p-phenylacetophenone (p-phenylphenacyl bromide). Suspend 36 g (0.183 mol) of p-phenylacetophenone in 200 ml of glacial acetic acid in a 500-ml flask, warm gently on a water bath until a clear solution results, then cool as far as possible without the formation of crystals. To this solution add 29.5 g (9.5 ml, 0.184 mol) of bromine do not allow the temperature to rise above 45 °C during the addition. The brominated product... 

A 5-ml volume of an ethanolic solution of acids (0.1 mol of each) is placed in a 50-ml flask and 5 ml of distilled water and several drops of 0.5% phenolphthalein solution are added. The solution is neutralized with several drops of 5 A KOH solution and made just acidic with 3 drops of 1 N HC1. Then 0.56 g of p-bromophenacyl or p-phenylphenacyl bromide is added, the mixture is refluxed for 10 min and the solid residue is dissolved by adding several millilitres of ethanol. The solution is cooled, 20 ml of ethyl acetate are added, followed by cold distilled water, the organic phase is separated, a portion of it is transferred into a test-tube with anhydrous sodium sulphate and the pure solution is injected. 

The procedure is similar to that given under 2 and 3 above. Add a weighed amount of acid (0-005 mol) to 5 ml. of water in a small conical flask and neutralise it with N sodium carbonate or N sodium hydroxide. The final solution should be faintly acid to litmus (add more of the organic acid or a few drops of dilute hydrochloric acid) unless this precaution is taken, coloured by-products are formed which are very difficult to remove. [If the alkali metal salt is available, dissolve 0 005 mol in 5 ml. of water, and render the solution just acid to litmus by the addition of dilute hydrochloric acid.] Introduce 10 ml. of alcohol, and if the salt of the organic acid is not thrown out of solution, add 0 005 mol of p-phenylphenacyl bromide reflux the mixture for periods up to 1,... 

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