Phenyl-2-acetate

P-Naphthyl acetate. Dissolve 5 0 g. of p-naphthol in 25 ml. of 10 per cent, sodium hydroxide solution in a 250 ml. reagent bottle, add 60 g. of crushed ice, and 5-7 g. (5 -5 ml.) of acetic anhydride. Shake vigorously for 10-15 minutes the p-naphth acetate separates as colourless crystals. Filter with suction, wash with water, drain and dry in the air. Recrystallise from light petroleum (b.p. 60-80°) or from dilute alcohol. The yield of pure product, m.p. 71°, is 6-5 g. 

Equip a 500 ml, three-necked flask with a separatory funnel, a mercury-sealed mechanical stirrer and a reflux condenser. Place a solution of 21 g. of sodium hydroxide in 200 ml. of water and also 47 g. of pure phenol in the flask, and stir the mixture cool the warm mixture to about 10° by immersing the flask in an ice bath. Place 63 g. (47 ml.) of dimethyl sulphate in the separatory funnel. 

CAUTION, Doth the vapour and the liquid dimethyl sulphate are highly poisonous. Inhalation of the vapour may lead to giddiness and even to more serious results. The cold liquid is easily absorbed through the skin, with toxic results. If the dimethyl sulphate is accidentally splashed upon the hands, wash immediately 

Add the dimethyl sulphate dropwise during 1 hour whilst stirring the mixture vigorously. Then reflux for 2 hours, with stirring, in order to complete the methylation. Allow to cool, add water, transfer to a separatory funnel, remove the lower layer, and wash once with water, twice with dilute sulphuric acid, and then with water until the washings are neutral to litmus. Add some sodium chloride to each washing as this will facilitate the separation of the two layers for anisole is 0- 996). Dry over anhydrous calcium chloride or magnesium sulphate, and distil from an air bath. Collect the anisole at 151-154°. The yield is 40 g. 

P-Naphthyl methyl ether (nerolin). Use 36-0 g. of p-naphthol, 10-5 g. of sodium hydroxide in 150 ml. of water, and add 31 -5 g. (23-5 ml.) of dimethyl sulphate whilst the mixture is cooled in ice. Warm for 1 hour at 70- 80°, and allow to cool. Filter off the naphthyl methyl ether at the pump, wash with 10 per cent, sodium hydroxide solution, then liberally with water, and drain thoroughly. RecrystaUise from benzene or methylated spirit. The yield is 33 g., m.p. 72°. 

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Pour the mixture into a separating-funnel. Owing to the density of the acetate being only slightly greater than that of water, a sharp separation is usually not rapidly obtained. It is advisable therefore to add about 8 ml. of carbon tetrachloride, when, after shaking, a sharp and rapid separation of the heavy solution of the phenyl acetate in the... 

Phenyl acetate is a colourless liquid, of b.p. 196° and ro8, almost insoluble in water and almost odourless. 

The ester and catalj st are usually employed in equimoleciilar amounts. With R =CjHs (phenyl propionate), the products are o- and p-propiophenol with R = CH3 (phenyl acetate), o- and p-hydroxyacetophenone are formed. The nature of the product is influenced by the structure of the ester, by the temperature, the solvent and the amount of aluminium chloride used generally, low reaction temperatures favour the formation of p-hydroxy ketones. It is usually possible to separate the two hydroxy ketones by fractional distillation under diminished pressure through an efficient fractionating column or by steam distillation the ortho compounds, being chelated, are more volatile in steam It may be mentioned that Clemmensen reduction (compare Section IV,6) of the hj droxy ketones affords an excellent route to the substituted phenols. 

To hydrolyse an ester of a phenol (e.g., phenyl acetate), proceed as above but cool the alkaline reaction mixture and treat it with carbon dioxide until saturated (sohd carbon dioxide may also be used). Whether a solid phenol separates or not, remove it by extraction with ether. Acidify the aqueous bicarbonate solution with dilute sulphuric acid and isolate the acid as detailed for the ester of an alcohol. An alternative method, which is not so time-consuming, may be employed. Cool the alkaline reaction mixture in ice water, and add dilute sulphuric acid with stirring until the solution is acidic to Congo red paper and the acid, if aromatic or otherwise insoluble in the medium, commences to separate as a faint but permanent precipitate. Now add 5 per cent, sodium carbonate solution with vigorous stirring until the solution is alkaline to litmus paper and the precipitate redissolves completely. Remove the phenol by extraction with ether. Acidify the residual aqueous solution and investigate the organic acid as above. 

Ingold and his co-workers used the competitive method in their experiments, in which nitration was brought about in acetic anhydride. Typically, the reaction solutions in these experiments contained o-8-I 4 mol of nitric acid, and the reaction time, depending on the reactivities of the compounds and the temperature, was 0-5-10 h. Results were obtained for the reactivities of toluene, > ethyl benzoate, the halogenobenzenes, ethyl phenyl acetate and benzyl chloride. Some of these and some later results are summarized in table 5.2. Results for the halogenobenzenes and nitrobiphenyls are discussed later ( 9.1.4, lo.i), and those for a series of benzylic compounds in 5,3.4. 

However, this method is appHed only when esterification cannot be effected by the usual acid—alcohol reaction because of the higher cost of the anhydrides. The production of cellulose acetate (see Fibers, cellulose esters), phenyl acetate (used in acetaminophen production), and aspirin (acetylsahcyhc acid) (see Salicylic acid) are examples of the large-scale use of acetic anhydride. The speed of acylation is greatiy increased by the use of catalysts (68) such as sulfuric acid, perchloric acid, trifluoroacetic acid, phosphoms pentoxide, 2inc chloride, ferric chloride, sodium acetate, and tertiary amines, eg, 4-dimethylaminopyridine. 

Phenyl acetate [122-79-2] M 136.2, b 78°/10mm, d 1.079, n 1.5039. Freed from phenol and acetic acid by washing (either directly or as a soln in pentane) with aqueous 5% Na2C03, then with saturated aqueous CaCl2, drying with CaS04 or Na2S04, and fractional distn at reduced pressure. 

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