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Properties.-Colourless liquid, with a pleasant aromatic smell; b. p. 179°; sp. gr. 10504 at 15°; it quickly oxidises in the air, forming benzoic acid; in contact with strong aqueous ammonia, crystals of hydrobenzamide are deposited. Add to a drop of the aldehyde in half a test-tube full of water a solution of 1 pt. phenylhydrazine hydrochloride, 1 pts. sodium acetate, and 8-10 pts. water. On shaking a thick white flocculent precipitate is formed (Fischer's reaction for aldehydes, Ber. 17, 574).

PREPARATION XXII.

BENZYL ALCOHOL, CH,O=CHCH2OH.

Literature.-Cannizzaro (1853), Ann. Ch. Pharm. 83, 129; and (1855) Ann. Ch. Pharm. 96, 216; R. Meyer (1881), Ber. 14, 2394.

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Forty grms. benzaldehyde, and a solution of 36 grms. caustic potash in 24 grms. water are shaken together in a well-stoppered bottle until a permanent emulsion is formed. The contents of the bottle after a short time become hot, and on standing for about twenty hours, solidify to a mass of white crystals of potassium.

benzoate. Water is added (about 200 c.c.) sufficient to dissolve the crystals, the benzyl alcohol also going into solution. The clear solution is extracted repeatedly with ether, the ether expelled and the colourless residual oil directly distilled without being previously dehydrated. As soon as the last traces of ether have passed over, the thermometer rises rapidly to the boiling point of benzyl alcohol and the whole distils within 2 to 3 degrees.

2C6H5CHO + KOH = CH,CH2(OH) + СÅH¿COOK Benzaldehyde Benzyl Alcohol

Potassium Benzoate.

Properties.-Colourless liquid with a faint aromatic smell; b. p. 206·5°; sp. gr. 1°0507 at 15 ̊4°.

PREPARATION XXIII.

a-TOLUIC ACID, CH2O2=CH,CH,CO2H.
(Phenylacetic Acid).

LITERATURE.-Cannizzaro (1855), Ann. Ch. Pharm. 96, 247; T. Maxwell (1879), Ber. 12, 1764; Spiegel (1881), Ber. 14, 239; Mann (1881), Ber. 14, 1645; Staedel (1886), Ber. 19, 1951.

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In a litre round-bottomed flask, to which a reflux condenser is attached, 60 grms. potassium cyanide, 99 per cent. are dissolved in 55 grms. water. A solution of 100 grms. benzylchloride in 100 grms. alcohol are poured slowly into the hot solution of potassium cyanide through the top of the condenser. The whole is then gently boiled for 3-4 hours on the sand-bath.* The liquid separates into two layers, and as the boiling continues the upper layer gradually assumes a brown colour, and at the same time crystals of potassium chloride separate out at the bottom of the vessel. the end of this time the flask is allowed to cool, and the upper dark brown liquid, consisting of an alcoholic solution of benzyl cyanide, decanted from the crystalline deposit of potassium chloride and distilled over wire gauze.* The thermometer stands for some time at about 80° until the alcohol is all off, a small quantity of water and benzyl cyanide distil at 100°; the temperature then rises quickly to 210°, and the fraction boiling at 210-235° consisting chiefly of benzyl cyanide is collected apart. It has a slightly brownish yellow colour. By the action of sulphuric acid it is converted into phenylacetic acid.

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50 grms. benzyl cyanide and 150 grms. of a mixture of 3 vol. conc. sulphuric acid and 2 vol. water are introduced into a litre flask, which is connected by a glass tube bent twice at right angles with a Woulff bottle. The end of this tube passes just beneath the cork in the one tubulus of the bottle which contains water. Through the second tubulus a vertical glass tube about foot long is fitted and dips just below the surface of the water. About the middle of the tube a large bulb is blown. The flask containing the mixture (which divides into two layers) is heated over the naked flame gently at first, and then the temperature gradually raised until small bubbles of gas are observed to rise from the surface of the lower layer of acid. The flame is now removed, and in a few minutes a strong reaction begins; the liquid boils and a small quantity of benzyl cyanide distils over into the Woulff bottle. At the same time the water is forced up the vertical tube into the bulb, which serves as a valve. The reaction is over in about half a minute; the flask is again heated for 2-3 minutes and then allowed to cool. On standing the liquid solidifies to a laminated crystalline mass. It is purified by washing with cold water. The crystals are dissolved in water, neutralised with sodium carbonate solution, the hot solution filtered and acidified with dilute sulphuric acid. On standing, colourless plates of the free acid separate which are filtered and washed. These may be

[blocks in formation]

SALICYLALDEHYDE (Ortho-oxybenzaldehyde).

PARA-OXYBENZALDEHYDE.
(1) OH (1).

CHO,=CH+ (z} CHO (4).

LITERATURE.-Reimer, Tiemann (1876), Ber. 9, 824; Tiemann, Herzfeld (1877), Ber. 10, 62 and 213.

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Fifty grms. phenol are dissolved in a solution of caustic soda containing 100 grms. caustic soda in 160 grms. water, and the whole introduced into a litre round-bottomed flask provided with a reflux condenser, and then heated to 50-60°. 75 grms. chloroform

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