HIPPURATES-BENZOGLYCOLIC ACID.

617

carefully avoiding any elevation of temperature, it produces a nitro-hippuric acid (HE,H,,NO,NO3), which, when the solution is diluted with three times its bulk of water, is gradually deposited in crystals. If the solution of this acid be boiled with sulphuric or hydrochloric acid, it is converted into nitrobenzoic acid and glycocine.

By boiling hippuric acid with a strong solution of potash, it is resolved into potassic benzoate and glycocine. It is also resolved into benzoic acid and glycocine when boiled with concentrated hydrochloric acid; and a similar change occurs if dilute sulphuric, nitric, or oxalic acid be employed instead of the hydrochloric.

Considerable difference of opinion has prevailed respecting the nature of hippuric acid, but the reaction of benzoyl chloride upon the compound of oxide of zinc with glycocine seems to favour the view that this acid is benzoyl-glycocine, or glycocine in which an atom of hydrogen has been displaced by its equivalent of benzoyl, the nearly neutral character of glycocine being changed to that of an acid by the addition of the electro-negative radicle benzoyl :

Glycocine.

HE2H,NO2

;

Hippuric acid, or benzoyl-glycocine.

3

This view is strengthened by the fact that when hippuric acid is boiled with peroxide of lead, carbonic anhydride is evolved, and benzamide is formed; the oxygen in the peroxide of lead producing the change in the manner illustrated by the following equation :

Hippuric acid,

Benzamide.

2 (H¤ ̧H ̧(¤‚H ̧Ð)NO2) + 3 →2 = 2 H2O + 4 €0, + 2 (H„N‚¤‚H ̧‡).

Dessaignes has also recently succeeded in procuring hippuric acid synthetically by exposing a mixture of equivalent quantities of glycocine and benzoic acid in a sealed glass tube for some hours to a temperature of 320° (160° C.) or upwards.

Cahours finds that by treating the compound of glycocine and zinc oxide with cumyl chloride and with anisyl chloride, he obtains crystalline acids corresponding to hippuric in compositioncuminuric acid, consisting of (HE,,H1NO), and anisuric acid of (HЄ10H10NO). 10NᎾ

(1443) Benzoglycolic Acid (H,H).—Strecker was disposed to regard hippuric acid as an amidated acid; and in order to test this theory he subjected it to the action of nitrous acid, which would liberate the dibasic acid of which it was supposed to be the amidic compound if this view were true. Instead of this

he obtained a new monobasic acid, which he termed the benzoglycolic, since it is evidently a compound of the benzoic and glycolic acids. Benzoglycolic acid may be obtained by exposing a solution of hippuric acid in nitric acid to the action of a current of nitric oxide, in which case nitrogen gas is evolved, and benzoglycolic acid is formed. This compound is produced by the reaction of nitrous acid upon hippuric acid, and the action of the nitric oxide on the nitric acid merely presents nitrous acid in the nascent condition to the hippuric acid; 4 NO+2 HNO3 + 2 H ̧Ð 6 HNO,. The reaction of nitrous acid upon hippuric acid may be thus represented :

=

Benzoglycolic acid crystallizes in rhomboidal prisms, or in thin plates. It is sparingly soluble in cold water, but is freely dissolved by alcohol and by ether. Boiling water also dissolves, but gradually decomposes it; if the acid be heated with a quantity of water insufficient for its solution, it melts to an oily-looking liquid; when heated with dilute acids, it is resolved into benzoic and glycolic acids :—

9

Strecker and Socoloff also obtained a compound of benzoic with lactic acid termed benzo-lactic acid (HEH,,), by heating the two acids together to about 360° (182° C.). It is analogous in properties to its homologue benzoglycolic acid.

2. Essence of Cumin-Cuminic Series.

(1444) Cumyl Hydride; Essence of Cumin; Cuminic Aldehyd (Є10H11,H=148); Sp. gr. of vapour 5*24; Rel. wt. 74; Boiling pt. 428° (220° C.).-The essential oil obtained by distilling the seeds of the Cuminum cyminum with water consists of a mixture of cumyl hydride and of a hydrocarbon (E1H11) termed cymol. The hydrocarbon is homologous with benzol (the hydrocarbon obtained by the distillation of dry calcic benzoate), and the oxidized portion is homologous with benzoyl hydride. Cumyl hydride is isomeric with essence of aniseed and of fennel.

10' 1

The two components of the oil of cumin may be readily separated by agitating this oil with a moderately concentrated

CUMINIC ACID-CUMINIC ALCOHOL-CUMYL.

619

solution of hydrosodic sulphite: a crystalline compound is thus formed which yields the pure cumyl hydride when heated with a solution of potash and submitted to distillation.

Cumyl hydride may be distilled unaltered in vessels from which air is excluded, but if exposed to the air it quickly absorbs oxygen and becomes brown, producing cuminic acid and a resinous compound. Oxidizing agents, such as nitric and chloric acids, also convert cumyl hydride into cuminic acid: if it be treated with caustic potash, potassic cuminate is produced, whilst hydrogen is liberated.

(1445) Cuminic Acid (HЄ10H112=164) may be prepared by decomposing potassic cuminate with hydrochloric acid. It crystallizes in colourless plates, which emit an odour resembling that of the common bug (cimex lectularius). Cuminic acid is fusible, and may be distilled unaltered at about 500° (260° C.). It is sparingly soluble in water, but freely so in alcohol and in ether. Fuming nitric acid converts it into nitro-cuminic acid. If distilled with an excess of caustic baryta it yields a hydrocarbon (E,H12) termed cumol, which is homologous with benzol. Cuminic anhydride may be obtained by decomposing dry sodic cuminate with phosphoryl chloride.

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The cuminates are monobasic; baric cuminate (Ba 2 €10H1102) forms beautiful iridescent plates: argentic cuminate is white, insoluble, and anhydrous; it speedily blackens by exposure to light.

(1446) Cuminic Alcohol [10H14; Boiling pt. about 470° (243° C.); Kraut] may be obtained by treating the essence with an alcoholic solution of potash in the manner directed for preparing benzoic alcohol (1438). It is a colourless oily liquid of an aromatic odour and burning taste: it may be distilled unchanged. It does not absorb oxygen when exposed to the air. When heated with caustic potash it yields cymol and cuminic acid. It does not form a colligated acid with sulphuric acid. Cuminic alcohol is isomeric with the oxidized component of oil of thyme.

11

(1447) Cumyl Cumylide, or Cumyl (Є10H11→)2.—When cumyl hydride is treated with potassium, hydrogen is evolved, and potassic cumylide (Є10H,K) is formed, constituting a gelatinous mass, 1 molecule of which rapidly absorbs 2 atoms of oxygen from the air, and is converted into potassic cuminate. Water decomposes it into caustic potash and cumyl hydride. When potassic cumylide is heated with cumyl chloride, mutual decomposition occurs, and cumyl is formed :

Cumyl may be obtained from the result of this reaction by treating the mass first with a weak solution of potash, in order to convert any undecomposed essence of cumin into potassic cuminate, and then agitating it with ether; the supernatant ethereal layer which contains the cumyl in solution is dried over chloride of calcium, and heated gently to expel the ether, when pure cumyl is left. Cumyl presents the appearance of a viscous oil which is heavier than water; when gently heated it emits an agreeable odour like that of the geranium. It is freely soluble in boiling alcohol, and cannot be distilled without undergoing decomposition; caustic potash converts it into potassic cuminate, whilst a portion of oil of cumin is simultaneously produced :—

(1448) Cumyl Chloride or Cuminic Oxychloride (E10H110,Cl =1825); Sp. gr. 1070; Boiling pt. about 495° (257° C.).—This is a colourless mobile liquid which is obtained by distilling cuminic acid with phosphoric chloride.

Many other compounds of the cuminic series may be formed, analogous to those of the benzoic series which have been already described.

9 9

The homologous oils, EH,,H, and €,H,,H, intermediate between hydride of benzoyl and hydride of cumyl, have not as yet been discovered, but the acid corresponding to the first of these, the toluic (or toluylic), is known. It may be procured by oxidizing cymol by long-continued boiling with nitric acid which has been diluted with about six times its bulk of water; and it is probable that by Piria's process of treating the calcium-salt of this acid with calcic formiate (note, p. 606), the aldehyd (or the missing hydride), Є.H,,H, would be obtained.

3. Essence of Cinnamon.-Cinnamic Series.

(1449) Oil of Cinnamon: Cinnamyl Hydride (E,H,O,H=132). -Essence of cinnamon and essence of cassia consist chiefly of cinnamyl hydride, with a small proportion of a hydrocarbon isomeric with oil of turpentine. The commercial essence has a sp. gr. varying between 1'025 and 1'05. It boils at from 430° to 445°. Cinnamyl hydride is readily obtained in a state of purity by

HYDRIDE OF CINNAMYL.

621

agitating the crude essence with a solution of hydropotassic sulphite. The crystalline product thus obtained must be pressed, washed with cold alcohol, and dried; after which it must be dissolved at a gentle heat in dilute sulphuric acid: the cinnamyl hydride then collects upon the surface of the liquid in the form of a colourless fragrant oil. This oil is slightly heavier than water; it absorbs oxygen rapidly from the air and becomes yellow, owing to the formation of a solid resin, mixed with cinnamic acid. Nitric acid combines with the hydride, and converts it into a solid mass of crystals. This compound is immediately decomposed by water into nitric acid and free cinnamyl hydride. Dumas made use of this fact in separating the hydride from its associated hydrocarbon.

If cinnamyl hydride be boiled with nitric acid, abundance of benzoyl hydride is evolved, and benzoic acid is found in the solution. If the essence be boiled with chloride of lime, calcic benzoate is produced. Chiozza has also made the interesting observation that benzoyl hydride may be converted into oil of cinnamon by dissolving the púre benzoyl hydride in aldehyd, and saturating the mixture with hydrochloric acid gas: on the application of a gentle heat the liquid becomes brown; and on afterwards proceeding to distillation, oil of bitter almonds first passes over, and then oil of cinnamon. Oil of cinnamon may,

in fact, be regarded as benzoyl hydride, in which an atom of hydrogen has been displaced by an equivalent of the hydrocarbon (HI), in which case the reaction in the foregoing experiment might be thus represented; water being eliminated under the influence of the hydrochloric acid, which is not indicated in the equation:

With ammonia the oil of cinnamon forms a crystalline solid termed cinnhydramide, which is analogous to hydroben

3

Several chlorinated substitution-compounds may be obtained from oil of cinnamon : one of these, chlorocinnose (Є,H,C,H), crystallizes in white needles, which are fusible, and may be volatilized without decomposition.

(1450) Cinnamic Acid (HE,H,O=148); Fusing pt. 264°