645 CINNAMIC GROUP. 1090. The chief representatives of the cinnamic group can be viewed as phenyl derivatives of allyl alcohol, acroleïn, and acrylic acid, just as the aromatic alcohols, aldehydes, and acids previously described may be considered as the phenyl substitution products of the alcohols CnH2n+ 1.OH, their aldehydes, and the fatty acids. The compounds in this group all contain phenyl in combination with a tricarbon nucleus, in which two of the carbon atoms are in divalent union. Cinnamic Alcohol. 1091. Styryl alcohol, or phenyl-allyl alcohol: C,H100 CH.CH: CH.CH2.OH, = is obtained by distillation of its cinnamate with potassic hydrate, also in smaller quantity by heating cinnamic aldehyde with alcoholic potassic bydrate (comp. § 1026). It crystallises in needles of hyacinthlike odour, melts at 33°, distils at 250°, is difficultly soluble in water, readily in alcohol and ether. It is converted into cinnamic acid on careful oxidation, and when treated with the halogen hydro-acids yields styryl haloids-e.g. styryl chloride, C,H,Cl, and styryl iodidewhich unite with ammonia to styryl ammonic chloride, C,H,NH,Cl, &c. On gentle heating of styryl alcohol and boron trioxide styryl ether, (C,H,)2O, is obtained as an oily liquid. 9 Styryl alcohol unites directly with bromine, when the two ingredients in solution in chloroform are mixed, forming cinnamic alcohol dibromide, or styryl dibromide hydrate, CH5.CHBr.CHBr.CH2.OH (comp. § 681), which crystallises from alcohol or ether in colourless needles or tables melting at 74°. By heating with concentrated hydrobromic acid it is converted into styryl tribromide: CH5.CHBr.CH Br.CH¿Br, forming shining needles, melting at 124°. This, on long heating with water, is converted into the trivalent alcohol: CH5.CH(OH).CH(OH).CH2(OH), stycerine, or phenyl glycerin, readily soluble in water and alcohol and left on evaporation as a gummy mass. 8 1092. Cinnamic allehyde, C,H,O= C6H5.CH: CH.CHO, forms the chief constituent of the essential oil of cinnamon and cassia; it is obtained by oxidation of cinnamic alcohol by aid of platinum black, and is prepared synthetically by saturation of a mixture of benzaldehyde and acetic aldehyde with hydrochloric acid (comp. § 765): CH .CHO + CH.CHO=H.0 +C H,CH:CH.CHO. It forms a difficultly soluble crystalline compound with hydric sodic sulphite, and can thus be readily separated from cinnamic alcohol and obtained on heating the purified crystals with soda solution. Cinnamic aldehyde is a colourless oil of strong cinnamon odour, heavier than water; on exposure to air it absorbs oxygen and is slowly converted into cinnamic acid. It boils at 247-248° with slight decomposition and volatilises readily in water vapour. It reacts with dry ammonia, yielding water and hydrocinnamide (comp. $ 1031): 3C ̧H ̧C2H„CHO + 2NH3 = 3H ̧O + (С ̧H ̧.С2H2.CH:)3N2. 1093. Cinnamic acid, C ̧H ̧0,=CH5.CH: CH.CO.OH, ß-phenyl acrylic acid, occurs naturally in balsams (storax, Tolu and Peru balsams) and resins (benzoin), and is formed by the oxidation of its alcohols and ethers, and synthetically by the action of sodium and carbonic anhydride on a-brom-styrolene (§ 1042): CH CH:CHBr + CO + Na =NaBr+CH.CH:CH.COONa; by heating benzaldehyde with chlor-acetal: CH .CHO + CH.CO.C1= HC1 + C H CH:CH.COOH; and by heating benzaldehyde with acetic anhydride and sodic acetate, the reaction in this case not being clearly understood. It can be prepared in largest quantity from storax. This is first heated with soda solution in a distilling vessel, when styrolene distils with the water vapour, whilst the free cinnamic acid goes into solution as sodic salt. The residue containing styracine is then boiled with concentrated solution of sodic hydrate, when styryl alcohol passes over. filtered solution of sodic salt is then decomposed by hydrochloric acid, the separated cinnamic acid puritied by solution in ammonia and reprecipitation and finally distilled. The Cinnamic acid, like benzoic acid, crystallises from boiling water in needles, from alcohol in large, readily cleavable rhombic prisms. It melts at 133°, boils at 290°, and is difficultly soluble in cold water. Its salts resemble those of benzoic acid. On gentle heating with dilute sulphuric acid and potassic chromate or permanganate it is first converted into benzaldehyde: CHẠCH:CH.CO.OH + 4 = C H .CHO + 2CO + H,O, and finally into benzoic acid. It unites with nascent hydrogen, forming 3-phenyl-propionic acid (§ 1074), and is decomposed on heating with lime into carbonic anhydride and styrolene (§ 1042), by fusion with potassie hydrate into benzoic and acetic acids (comp. § 790): C_H_CH:CH.00.0K + HOK + H_0=C H..CO.OK +CH CO.OK + Hg. 1094. Ethereal salts of cinnamic acid are prepared like those of other monobasic acids. Ethylie cinnamate, C,H-0.0.C,H,, is an oil boiling at 267°. Benzylic cinnamate, C,H,O.O.CH.C6H5, or cinnamein, occurs naturally in Tolu and Peru balsams; it crystallises in shining prisms, melts at 39°, and can only be distilled unchanged under reduced pressure. Cinnamic cinnamate: C6H5.C2H2.CO.O.CH2.C2H.C6H5, or styracine, is contained in large quantity in storax, and is left as a colourless mass after long digestion with soda solution. It crystallises from ether alcohol in groups of fine needles and melts at 44°. Cinnamic anhydride, (C6H5.C2H2.CO)2O, is obtained in colourless. crystals by the action of phosphoric oxychloride on sodic cinnamate; it melts at 127° and is nearly insoluble in alcohol. Phosphoric chloride converts cinnamic acid into chlor-cinnamyl : C6H5.C2H2.CO.CI, a heavy yellow oil, boiling at 260°-262°. Water slowly converts it into cinnamic and hydrochloric acids; with alcohol it gives ethylic cinnamate, and ammonia gas converts it into cinnamide: C6H5.C2H2.CO.NH2, a crystalline mass closely resembling benzamide. Isomers of Cinnamic Acid. 1095. Atropic and isatropic acids are obtained together by heating tropic acid with baryta or hydrochloric acid, and are therefore also formed in the preparation of tropic acid from atropine. Atropic acid is obtained in largest quantity when baryta is used, whilst hydrochloric acid gives principally isatropic acid. Atropic acid, a-phenyl acrylic acid, crystallises in monoclinic tables; it melts at 106-107°, is moderately soluble in hot water, but requires 700-800 parts of cold water for solution. Its formation is represented by the equation : C&HS.CH CH2.OH 2 = H2O+CH.C:CH2 It unites with nascent hydrogen, forming a-phenyl-propionic acid (§ 1074); fusion with potassic hydrate converts it into phenyl-acetic and formic acids; chromic acid oxidises it into benzoic acid, carbonic anhydride, and water. Isatropic acid crystallises in thin rhombic plates, is more difficultly soluble in water than the preceding, melts at 200°, is not oxidised by chromic acid, and does not combine with nascent hydrogen. From these reactions it is probably a polymer (diatropic acid?) Addition Products of Cinnamic Acid. 1096. Cinnamic acid combines with hydrogen (as already mentioned), the halogens, hydrogen haloids, and hypochlorous acid. Cinnamic acid dibromide, a-phenyl-dibrom-propionic acid : C.H..CHBr.CHBr.CO.OH, is obtained by addition of bromine to a solution of cinnamic acid in carbonic disulphide; it crystallises in colourless rhombic plates and is insoluble in cold water. On boiling with water it yields partly B-brom-styrolene, carbonic anhydride, and hydrobromic acid : CH.CHBr.CH Br.CO.OH CH5.CBr:CH2 + CO2 + HBr, partly hydrobromic acid and = Phenyl-brom-lactic acid, CH5.CH Br.CH(OH).CO.OH, in the form of hexagonal tables containing water of crystallisation; when anhydrous it melts at 125°. Phenyl-chlor-lactic acid, CH5.CHCI.CH(OH).CO.OH, is the addition product of hypochlorous acid with cinnamic acid, and is most readily obtained when a solution of equal molecules of sodic carbonate and cinnamate is saturated with chlorine, the solution of sodic salts acidulated with hydrochloric acid, and after evaporation extracted with ether. The acid crystallises with one molecule of water in hexagonal plates, and then melts at 70°-80°; when anhydrous it melts at 104°. Aqueous solutions of both phenyl halogen lactic acids are converted by sodium amalgam into phenyl lactic acid. Substitution Products of Cinnamic Acid. 1097. Two varieties are known, according as the substitution occurs in the CH, group or in the benzene nucleus. The first includes both the isomeric Phenyl brom-acrylic acids: CH.CH:CBr.CO.OH and CH5.CBr: CH.CO.OH. They are both formed at the same time by the decomposition of cinnamic acid dibromide with alcoholic potassic hydrate, and are separated by aid of their ammonic salts. The acid of the difficultly soluble salt, commonly termed a-brom-cinnamic acid, crystallises in long shining needles, melts at 130°-131°, and can be volatilised unchanged, whilst the acid of the more readily soluble salt, 3-bromcinnamic acid, crystallises in hexagonal plates, melts at 120°, and is converted into the isomeric a-acid on distillation. 1098. The second variety of substitution products are represented by the nitro-cinnamic acids, the coumaric acids, and their derivatives. Nitro-cinnamic acids, CH,(NO2).C2H.CO.OH, are formed by the slow addition of cinnamic acid to cold concentrated nitric acid, which must be free from nitrous acid in order to prevent oxidising action. In order to separate the resulting isomers they are converted into ethylic salts, of which one, ethylic paranitro-cinnamate, is nearly insoluble in alcohol, whilst ethylic orthonitro-cinnamate is readily By saponification of these bodies and decomposition of the aqueous solutions of the alkali salts with mineral acids the insoluble free nitro-cinnamic acids are obtained. Paranitro-cinnamic acid crystallises in fine needles; it melts at 265° and is very difficultly soluble in alcohol. Orthonitro-cinnamic acid is more readily soluble in alcohol; it melts at 232°. On oxidation the first is converted into para, the latter into ortho-nitro benzoic acid. Tin and hydrochloric acid convert the nitro-cinnamic acids into amido-cinnamic acids, CH(NH2).C ̧H ̧.CO.OH. Cinnamic acid dissolves in Nordhausen sulphuric acid, yielding sulpho-cinnamic acid, CH,(SO2.OH).C2H2.CO.OH, which crystallises in prisms with 3H2O. It is readily soluble in water and generally yields soluble salts. Hydroxy-Cinnamic Acids. .OH 1099. Monhydroxy-cinnamic acids, CHC2H2.CO.OH 1. Coumaric acid, or orthohydroxy-cinnamic acid, occurs, together with hydro-coumaric acid, in Melilotus officinalis, and is readily obtained by boiling coumarine with alkalies. It crystallises in colourless prisms, readily soluble in alcohol and hot water; it melts at 195° and is decomposed into potassic acetate and salicylate on heating with potassic hydrate. Its alkali salts show a fine fluorescence in aqueous solution. Ferric chloride gives no violet colour with it. Coumarine, C,H6O2, an ethereal anhydride of coumaric acid : corresponding to lactide and salicylide (§ 1062), occurs in Asperula odorata, Melilotus officinalis, Anthoxanthum odoratum, and especially in tonka beans, the fruit of Dipterix odorata, in the latter frequently in fine crystals. It is extracted by alcohol, and after evaporation of the greater part of the solvent separated by addition of water and cooling. It crystallises in colourless prisms of very agreeable odour, is difficultly soluble in cold water; it melts at 67° and boils at 290o. It unites with chlorine and bromine, forming dihaloids, e.g. or (by also uniting with water) the respective coumaric acids. The synthesis of coumarine and its homologues (which latter do not occur naturally) by heating sodium salicylic aldehyde (§ 1033) with the anhydrides of the acetic series is very interesting. Acetic anhydride so treated gives coumarine : .O--CO .CO.CH3 CHCHO .ONa +OCO.CH, = NaO.CO.CHg + CH .CH: CH + H2O. Butyric anhydride gives a body melting at 70°-71° and boiling at 296°, probably ethyl coumarine : Isovaleric anhydride gives a compound C12H12O2, forming long prisms, melting at 54° and boiling at 301°, probably isopropyl coumarine, &c. |