fulvenes, substances characterized by their intense orange-red colour HC;CH
(J. Thiele, Bef., 1900, 33, p. 669). Phenylfulven, | C:CHPh, HC:CH/
obtained from benzaldehyde and cyclo-pentadiene, forms dark red plates. Diphenylfulven, from benzophenone and cyclo-pentadiene, crystallizes in deep red prisms. Dimethylfulven is an orange coloured oil which oxidizes rapidly on exposure. Concentrated sulphuric acid converts it into a deep red tar. Cyclo-penlanone, CEHSO, first prepared pure by the distillation of calcium adipate (J. l/Vislicenus, Arm., 1893, 275, p. 312), is also obtained by the action of sodium on the esters of pimelic acid; by the distillation of calcium succinate; and by hydrolysis of the cyclopentanone carboxylic acid, obtained by condensing adipic and oxalic esters in the presence of sodium ethylate. Reduction gives cyclo-pentanol, C5H9OH.
Croconic acid (dioxy-cyclo-pentene-trione), C5H2O5, is formed when triquinoyl is boiled with water, or by the oxidation of hexa-oxybenzene or dioxydiquinoyl in alkaline solution (T. Zincke, Bef., 1887, 20, p. 1267). It has the character of a quinone. On oxidation it yields cyclo-pentane-pentanone (leuconic acid). Derivatives of the cyclo-pentane roup are met with in the breaking-down products of the terpenes (ia).
Campholactone, C, H14O2, is the lactone of trim ethyl-2-2-3-cyclopentanol-5-carboxylic acid-3. For an isomer, isocampholactone
(the lactone of trim ethyl-2-2-3-cyclo-pentanol-3-carboxylic acid-1) see W. H. Perkin, jun., Proc. Chem. Soc., 1903, 19, p. 61. Lauronolic acid, CQHHOQ, is trim ethyl-2~2-3-cyclo-pentene-4~acid-I. Isolauronolic acid, C9H14()¢, is trim ethyl-2-2-3-cyclo-pentene-3-acid-4. Campholic acid, C101-I, gO2, is tetra methyl-1-2-2-3-cyclo-pentane acid-3. Camphononic acid, C, H14O3, is trim ethyl-2-2~3-cyclo-pentanone-1-carboxylic acid-3. Camphorphorone, CQHUO, is methyl-2isobuty-lene-5-cyclo-pentanone-1. Isothujone, CWHNO, is dimethyl-1~2-isopropyl-3-cyclo-pentene-I-one-5. (F. W. Semmler, Bef.,
19001 33, P~ 275-)
L. Bouveault and G. Blanc (Comples rendus, 1903, 136, p. 1460), prepared hydrocarbons of the cycle-pentane series from cyclohexane compounds by the exhaustive methylation process of A. W Hofmann (see PYRIDINE). For phenyl derivatives of the cyclopentane group see F. R. Japp, Jour. Chem. Soc., 1897, 71, pp. 139, 144; H. Stobbe, Ann., 1901, 314, p. III; 315, p. 219 seq.; 1903 326. P~ 3471
H hydrocarbons.-Cyclo-hexane, or hexahydro benzene, CSHW, is obtained by the action of sodium on a boiling alcoholic solution of 1~6-dibromhexane, and by passing the vapour of benzene, mixed with hydrogen, over finely divided nickel. It is a liquid with an odour like that of benzene. It boils at 80-81° C. Nitric acid oxidizes it to adipic acid. When heated with bromine in a sealed tube for some days at 150-200° C., it yields 1~2-4~5-tetrabrombenzene (N. Zelinsky, Ber., 1901, 34, p. 2803). It is stable towards halogens at ordinary temperature. Benzene hexachloride, C, H, ,Cl5, is formed by the action of chlorine on benzene in sunlight. By recrystallization from hot benzene, the a form is obtained in large prisms which melt at 157° C., and at their boiling-point decompose into hydrochloric acid and trichlorbenzene. The B form results by chlorinating boiling benzene in sunlight, and may be separated from the a. variet by distillation in a current of steam. It sublimes at about 310° Similar varieties of benzene hexabromide are known. Hexahydrocymene (methyl-1-isopropyl-4-cyclo-hexane), C10H2°, is important since it is the parent substance of many terpenes (.v.). It is obtained by the reduction of I-4 dibrommenthane with sodium (J. de Montgoliier, Ann. chim. ghys., 1880 , 19, p. 158), or of cymene, limonene, &c., by Sa atier and Senderens's method. It is a colourless liquid which boils at 180° C. Cyclo-hexene (tetra hydro benzene), CGHW, was obtained by A. v. Baeyer by removing the elements of hydriodic acid from iodocyclo-hexane on boiling it with quinoline. It is a liquid which boils at 82° C. Hypochlorous acid converts it into 2-chlor-cyclo-hexanol-1, whilst potassium perman anate oxidizes it to cyclo-hexandi-ol. Cyclo-hexadiene (dihycirobenzene), CGH8.-Two isomers are possible, namely cyclo-hexadiene-1-3 and cyclo-hexadiene-1-4. A. v. Baeyer obtained what was probably a mixture of the two by heating 1-4 dibrom-cyclo-hexane with quinoline. C. Harries (Ann., 1903, 328, p. 88) obtained them tolerably pure by the dry distillation of the phosphates of I-3-diamino and 1-4-diamino-cycle-hexane. The 1-3 compound boils at 81-82° C. and on oxidation yields succinic and oxalic acids. The 1-4 compound also boils at 81-82° C. and on oxidation gives succinic and malonic acids.
Alcohols.—Cyclo-hexanol, CQHUOH, is produced by the reduction of the corresponding ketone, or of the iodhydrin of quinite. Nitric acid oxidizes it to adipic acid, and chromic acid to c clo-hexanone. Qumite (cyclo-hexanediol-1-4) is prepared by reducing the corresponding ketone with sodium amalgam, cis-, and trans-modifications being obtained which may be separated by their acetyl derivatives. Phloroglucite (cyclo-hexane-triol-1-3-5) is obtained by reducing an aqueous solution of hloroglucin with sodium (W. Wislicenus, Bef., 1894, 27, p. 357). (Suercite (cycle-hexane-pentol-1-2-3-4-5), isolated from acoms in 1849 by H. Braconnot (Ann. chim. phys. , 27, p. 392), crystallizes in colourless prisms which melt at 234° C. When heated in vacuo to 240° C. it yields hydro quin one, quinone and pyrogallol. It is dextro-rotatory. A laevo-form occurs in the geaves of giymnema sylvestre (F. B. Power, Journ. Chem. Soc., 1904, 2 .
5I1i)ositelicyclo-hexane-hexol), C.~, H6(OH)6.-The inactive form occurs in the muscles of the heart and in other parts of the human body. The d-form is found as a methyl ether in pinite (from the juice of Pinus lambertina, and of caoutchouc from Mateza roritina of Madagascar), from which it may be obtained by heating with hydriodic acid. The I-form is also found as a methyl ether in quebrachite. B y mixing the d- and l- forms, a racemic variety melting at 253° C. is obtained. A dimethyl ether of inactive inosite is dambonite which occurs in caoutchouc from Gabon.
Ketones.-Cyclo-hexanone, CGHNO, is obtained by the distillation of calcium pimelate, and by the electrolytic reduction of phenol, using an alternating current. It is a colourless liquid, possessing a peppermint odour and boiling at 155° C. Nitric acid oxidizes it to adipic acid. It condenses under the influence of sulphuric acid to form dodecahydrotriphenylene, C181-124, and a mixture of ketones (C. Mannul, Ber., 1907, 40, p. 153). Methyl-1-cyclo-hexanone-3, CH, ~C6H, O, is prepared by the hydrolysis of pulegone. It is an optically active liquid which boils at 168-169° C. Homologues of menthone may be obtained from the ketone by successive treatment with sodium amide and alkyl halides (A. Haller, Complex fendus, 1905, 140, p. 127). On oxidation with nitric acid (sp. gr. 1-4) at 60-70° C., a mixture of -and- -methyl adipic acids is obtained (W. Markownikoff, Ann., 1905, 236, p. 299). It can be transformed into the isomeric methyl-1-cyc1o- xanone-2 (O. Wallach, Ann., 1904, 329, p. 368). For methyl-1-cyclo-hexanone-4, obtained by distilling ~/-methyl pimelate with lime, see O. Wallach, Bef., 1906, 39, p. 1 92. ~
C4clo-hexane-dione-1-3 (dihydroresorcin), C¢H@O¢, was obtained by Merling (Ami, 1894, 278, p. 28) by reducing resorcin in hot alcoholic solution with sodium amalgam. Cyclo-hexane-dione-1~4 is obtained by the hydrolysis of succino-succinic ester. On reduction it yields quinite. It combines with benzaldehyde, in the presence of hydrochloric acid, to form 2-benzyl-hydro quin one. Cyclohexane-trione-1»3-5 (phloroglucin) is obtained by the fusion of many resins and of resorcin with caustic alkali. It may be prepared synthetically by* fusing its dicarboxylic ester (from malonic ester and sodio malonic ester at 145° C.) with potash (C. W. Moore, Journ. Chem. Soc., 1904, 85, p. 165). It crystallizes in prisms, which melt at 218° C. With ferric chloride it gives a dark violet coloration. It exhibits tautomerization, since in many of its reactions it shows the properties of a hydroxylic substance. Rhodizonic acid (dioxydiquinoyl), C6H2O5, is probably the enolic form of an oxypentaketo-cyclo-hexane. It is formed by the reduction of triquinoyl by aqueous sulphurous acid, or in the form of its potassium salt by washing potassium hexa-ox benzene with alcohol (R. Nietzki, Bef., 1885, 18, pp. 513, 1838§ . Triquinoyl (hexaketo-cyclo-hexane) C506-8H2O, is formed on oxidizing rhodizonic acid or hexa-oxybenzene. Stannous chloride reduces it to hexa-oxybenzene, and when boiled with water it yields croconic acid (dioxy-cyclo-pentene-trione).-Cyclo-hexenones.—Two types of ketones are to be noted in this
group, namely the aB and By ketones, depending upon the position of the double linkage in the molecule, thus:
CH, ' CH CH-CH,
H c / ' co HC/ c0
2 CH2-CH2/ CH2-CH2/
These two classes show characteristic differences in properties. For example, on reduction with zinc and alcoholic potash, the a|8 compounds give saturated ketones and also bi-molecular compounds, the By being unaffected; the B-y series react with hydroxylamine in a normal manner, the 11,8 yield oxamino-oximes. M ethyl-1-cyclo-hexene-1-one-3, CH3-C6H7O, is obtained by condensing sodium aceto-acetate with methylene iodide, the ester so formed being then hydrolysed. Isocamphorphofone, CQHHO, is trim ethyl 1-6-6.-cyclo-hexene-1-one 6. Isocamphor, CwH,6O, is methyl-1isopropyl-3-cyclo-hexene-I-one 6.
Acids.-Hexahydrobenzoic acid, C6H,1-CO¢H, is obtained by the reduction of benzoic acid, or by the condensation of I-5 dibrompentane with disodio-malonic ester. It crystallizes in small plates which melt at 30-31° C. and boil at 232-233° C. (J. C. Lumsden, Joum. Chem. Soc., 1905, 87, p. 90). The sulphochloride of the acid on reduction with tin and 'hydrochloric acid gives hexahydrothiophenol, CGHHSH, a colourless oil which boils at 158-160° C. (W. Borsche, Bef., 1906, 39, p.
Quinic acid, C6 1 OH)¢CO2H (tetra-oxy-cyclo-hexane carboxylic acid), is found in cofiee beans and in quinia bark. It crystallizes in colourless prisms and is optically active. When heated to about 250° C. it is transformed into quinide, probably a lactone, which on heating with baryta water gives an inactive quinic acid. Hexahydrophthalic acids, C6H10(CO2H)¢ (cyclo-hexanedicarboxylic acids).-Three acids of this group are known, containing the Carboxyl-groups in the 1-2, 1~3, and 1-4 ositions, and each exists in two stereo-isomeric forms (cis- and trans-g. The an hydride of the cis-1»2