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Polymethylenes

General Methods of Formation

Hydrocarbons may be obtained from the dihalogen paraffins by the action of sodium or zinc dust, provided that the halogen atoms are not attached to the same or to adjacent carbon atoms (A. Freund, Monats., 1882, 3, p. 625; W. H. Perkin, jun., Journ. Chem. Soc., 1888, 53, p. 213) - CH2CH2Br +2Na=2NaBr-? C 2; CH 2 CH 2 Br H2.cH2 by the action of hydriodic acid and phosphorus or of phosphonium iodide on benzene hydrocarbons (F. Wreden, Ann., 1877, 187, p. 153; A. v. Baeyer, ibid., 1870, 155, p. 266), benzene giving methylpentamethylene; by passing the vapour of benzene hydrocarbons over finely divided nickel at 180-250° C.

(P. Sabatier and J. B. Senderens, Comptes rendus, 1901, 132, p. 210 seq.); and from hydrazines of the type CnH2,2_1NHNH2 by oxidation with alkaline potassium ferricyanide (N. Kijner, Journ. prak. Chem., 1901, 64, p. 113). Unsaturated hydrocarbons of the series may be prepared from the corresponding alcohols by the elimination of a molecule of water, using either the xanthogenic ester method of L. Tschugaeff (Ber. 18 99, 3 2, p. 333 2): Cn112n_10Na - >C,,H2n_10CS.SNa(R) -->Cn,H 2 n_2+COS- FRSH; or simply by dehydrating with anhydrous oxalic acid (N. Zelinsky, Ber., 1901, 34, p. 3 2 49); and by eliminating the halogen acid from monoor di-halogen polymethylene compounds by heating them with quinoline.

Alcohols are obtained from the corresponding halogen compounds by the action of moist silver oxide, or by warming them with silver acetate and acetic acid; by the reduction of ketones with metallic sodium; by passing the vapours of monohydric phenols and hydrogen over finely divided nickel (P. Sabatier and J. B. Senderens, loc. cit.); by the reduction of cyclic esters with CH 2CH2 / NCH2--CHI sodium and alcohol (L. Bouveault and G. Blanc, Comptes rendus, 1903, 136, p. 1676; 137, p. 60); and by the addition of the elements of water to the unsaturated cyclic hydrocarbons on boiling with dilute acids.

Aldehydes and Ketones.-The aldehydes are prepared in the usual manner from primary alcohols and acids. The ketones are obtained by the dry distillation of the calcium salts of dibasic saturated aliphatic acids (J. Wislicenus, Ann., 18 93, 275, p. 309): [ CH 2 CH 2 CO 2 ] 2 Ca---[CH 2 CH 2 ] 2 CO; by the action of sodium on the esters of acids of the adipic and pimelic acid series (W. Dieckmann, Ber., 1894, 27, pp. 103, 2 475): CH 2 CH 2 CH2 CO,R CH2CH2CH2 CH2 CH2 C02R 7->CH2CH2CO by the action of sodium ethylate on 3-ketonic acids (D. Vorldnder, Ber., 1895, 28, p. 2348): CH 2 ,CH2CH2 CO 2 H-? CH 2 ? CH2 CHz?CU; COCH 3 COCH2 from sodio-malonic ester and 0-unsaturated ketones or ketonic esters: /CH, CO (R02C)2CH2+ PhCH :CH /CH:>; CH(C02R)C07 from aceto-acetic ester and esters of a$-unsaturated acids, followed by elimination of the carboxyl group: CH2CR', CH 3 COCH 2. CO 2 R+R' 2 C: CH.C02R_CO ? - ? Chc02r; CH 2 CO / by the condensation of two molecules of aceto-acetic ester with aldehydes followed by saponification (E. Knoevenagel, Ann., 1894, 281, p. 25; 1896, 288, p. 321; Ber., 1904, 37, P. 4461): CH2CHR' 2CH3. CO. CH 2 CO 2 R-[[FohcR'-*Ch 3 C]]? .

CH -CO CH2 from 1.5-diketones which contain a methyl group next the keto-group (W. Kerp, Ann., 1896, 290, p. 123): CH2C(CH3) 3CH3COCH3-(CHa)2C? ??CH CH 2 COQ by the condensation of succinic acid with sodium ethylate, followed by saponification and elimination of carbon dioxide:- 2C2H4(COzH) C 2 - H2 CH 2 CO CO. CH 2 CH 2 ' and from the condensation of ethyl oxalate with esters of other dibasic acids in presence of sodium ethylate (W. Dieckmann, Ber., 18 97, 3 0, p. 1 47 0; 18 99, 3 2, P. 1 933): CO 2 R ,C02R COCH2?

CH C02R +CH2 'CO 2 R - ? COCH2?2.

Acids may be prepared by the action of dihalogen paraffins on sodio-malonic ester, or sodio-aceto-acetic ester (W. H. Perkin, jun., Journ. Chem. Soc., 1888, 53, p. 1 94): C2H4Br2+2NaCH(C02R)2--->(CH 2) 2 C(CO 2 R) 2 +CH 2 (CO 2 R) 2; ethyl butane tetracarboxylate is also formed which may be converted into a tetramethylene carboxylic ester by the action of bromine on its disodium derivative (W. H. Perkin and Sinclair, ibid., 1829, 61, p. 36). The esters of the acids may also be obtained by condensing sodio-malonic ester with a-halogen derivatives of unsaturated acids: CH H?C02R CH 3 CH: CBrCO 2 R+NaCH (CO 2 R) 2 --->CH 3 C. I C(C02R)2 by the action of diazomethane or diazoacetic ester on the esters of unsaturated acids, the pyrazoline carboxylic esters so formed losing nitrogen when heated and yielding acids of the cyclo- propane series (E. Buchner, Ber., 1890, 23, p. 703; Ann., 1895, 284, p. 212; H. v. Pechmann, Ber., 18 94, 2 7, p. 1891): CHCO 2 R N:NCH CO 2 R [[Chc02r Ch 2 N 2 + !'. ---? I I -* H2c]]?

CHCO 2 R H 2 C-CHCO 2 R Chc02r and by the Grignard reaction (S. Malmgren, Ber., 1903, 36, pp. 668, 2622; N. Zelinsky, ibid., 1902, 35, p. 2687).

Cyclo-propane Group. Trimethylene, Calls, obtained by A. Freund (Monats., 1882, 3, p. 625) by heating trimethylene bromide with sodium, is a gas, which may be liquefied, the liquid boiling at -35° C. (749 mm.). It dissolves gradually in concentrated sulphuric acid, forming propyl sulphate. Hydriodic acid converts it into n-propyl iodide. It is decomposed by chlorine in the presence of sunlight, with explosive violence. It is stable to cold potassium permanganate.

Cyclo-propane carboxylic acid, C 3 H 5 CO 2 H, is prepared by heating the 1.1- dicarboxylic acid; and by the hydrolysis of its nitrile, formed by heating y-chlorbutyro-nitrile with potash (L. Henry and P. Dalle, Chem. Centralblatt, 1901, I, p. 1357; 1902, 1, p. 913). It is a colourless oil, moderately soluble in water.

The '1.1' dicarboxylic acid is prepared from ethylene dibromide and sodio-malonic ester. The ring is split by sulphuric or hydrobromic acids. The cis 1.2-cyclo-propane dicarboxylic acid is formed by eliminating carbon dioxide from cyclo-propane tricarboxylic acid -1.2.3 (from 43-dibrompropionic ester and sodio-malonic ester). The trans-acid is produced on heating pyrazolin-4.5-dicarboxylic ester, or by the action of alcoholic potash on a-bromglutaric ester. It does not yield an anhydride.

Cyclo-butane Group. Cyclo-butane, C 4 H 8, was obtained by R. Willstatter (Ber., 1907, 4 0, p. 3979) by the reduction of cyclobutene by the Sabatier and Senderens method. It is a colourless liquid which boils at 11 -12° C., and its vapour burns with a luminous flame. Reduction at 180200° C. by the above method gives n-butane.

Cyclo-butene, C4H6, formed by distilling trimethyl-cyclo-butylammonium hydroxide, boils at 1.5-2.0° C. (see N. Zelinsky, ibid., P. 4744; G. Schweter, ibid., p. 1604).

When sodio-malonic ester is condensed with trimethylene bromide the chief product is ethyl pentane tetracarboxylate, tetramethylene dicarboxylic ester being also formed, and from this the free acid may be obtained on hydrolysis. It melts at 154-156° C., losing carbon dioxide and passing into cyclo-butane carboxylic acid, C 4 H 7 CO 2 H. This basic acid yields a monobrom derivative which, by the action of aqueous potash, gives the corresponding hydroxycyclo-butane carboxylic acid, C 4 H 6 (OH)CO 2 H. Attempts to eliminate water from this acid and so produce an unsaturated acid were unsuccessful; on warming with sulphuric acid, carbon monoxide is eliminated and cyclo-butanone (keto-tetramethylene) is probably formed.

The truxillic acids, C,8H1504, which result by the hydrolytic splitting of truxilline, C38H46N208, are phenyl derivatives of cyclo-butane. Their constitution was determined by C. Liebermann (Ber., 1888, 21, p. 2342; 1889, 22, p. 124 seq.). They are polymers of cinnamic acid, into which they readily pass on distillation. The a-acid on oxidation yields benzoic acid, whilst the 1 3-acid yields benzil in addition. The a-acid is diphenyl-2.4-cyclo-butane dicarboxylic acid -1.3; and the /3-acid diphenyl-3.4-cyclo-butane dicarboxylic acid -1.2. By alkalis they are transformed into stereo-isomers, the a-acid giving 7 -truxillic acid, and the ,3-acid S-truxillic acid. The a-acid was synthesized by C. N. Riiber (Ber., 1902, 35, p. 2411; 1904, 37, P. 22 74), by oxidizing diphenyl-2.4-cyclo-butane-bismethylene malonic acid (fron cinnamic aldehyde and malonic acid in the presence of quinoline) with potassium permanganate.

Cyclo-pentane Group. Derivatives may be prepared in many cases by the breaking down of the benzene ring when it contains an accumulation of negative atoms (T. Zincke, Ber., 1886-1894; A. Hantzsch, Ber., 1887, 20, p. 2780; 1889, 22, p. 1238), this type of reaction being generally brought about by the action of chlorine on phenols in the presence of alkalis (see Chemistry: Organic). A somewhat related example is seen in the case of croconic acid, which is formed by the action of alkaline oxidizing agents on hexa-oxybenzene HOCC(OH): C(OH) HOCCOCO HOCCO 1 -* --j p_)CO HO. C. C(OH): C(OH) HOCCOCO HOCCO/ Hexa-oxybenzene. Rhodizonic acid. Croconic acid.

Cyclo-pentane, C5H10, is obtained from cyclo-pentanone by reducing it to the corresponding secondary alcohol, converting this into the iodo-compound, which is finally reduced to the hydrocarbon (J. Wislicenus, Ann., 18 93, 2 75, p. 327). It is a colourless liquid which boils at 50-51° C. Methyl-cyclo-pentane, C 5 H 9 CH 3, first obtained by F. Wreden (Ann., 1877, 187, p. 163) by the action of. hydriodic acid and red phosphorus on benzene, and considered to be hexahydrobenzene, is obtained synthetically by the action of sodium on 1.5 dibromhexane; and by the action of magnesium on acetylbutyl iodide (N. Zelinsky, Ber., 1902, 35, p. 2684). It is a liquid boiling at 72° C. Nitric acid (sp. gr. 1.42) oxidizes it to succinic and acetic acids. Cyclo-pentene, C 5 H 8, a liquid obtained by the action of alcoholic potash on iodo-cyclo-pentane, boils at 45° C. Cyclopentadiene, C. 1 H 6, is found in the first runnings from crude benzene distillations. It is a liquid which boils at 41° C. It rapidly polymerizes to di-cyclo-pentadiene. The -CI-1 2. group is very reactive and behaves in a similar manner to the grouping COCH 2 COin open chain compounds, e.g. with aldehydes and ketones it gives the fulvenes, substances characterized by their intense orange-red colour HC: CH (J. Thiele, Ber., 1900, 33, p. 669). Phenylfulven, j " > C :CHPh, HC: CHI obtained from benzaldehyde and cyclo-pentadiene, forms dark red plates. Diphenylfulven, from benzophenone and cyclo-pentadiene, crystallizes in deep red prisms. Dimethylfulven is an orangecoloured oil which oxidizes rapidly on exposure. Concentrated sulphuric acid converts it into a deep red tar.

Cyclo-pentanone, C 5 H 8 0, first prepared pure by the distillation of calcium adipate (J. Wislicenus, Ann., 18 93, 2 75, 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, C5H90H.

Croconic acid (dioxy - cyclo-pentene-trione), C 5 H 2 0 51 is formed when triquinoyl is boiled with water, or by the oxidation of hexa-oxybenzene or dioxydiquinoyl in alkaline solution (T. Zincke, Ber., 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 group are met with in the breaking-down products of the terpenes.

Campholactone, C9H1402, is the la.ctone of trimethyl-2.2. 3-cyclopentanol-5-carboxylic acid-3. For an isomer, isocampholactone (the lactone of trimethyl-2.2. 3-cyclo-pentanol-3-carboxylic acidI) see W. H. Perkin, jun., Proc. Chem. Soc., 1903, 19, p. 61. Lauronolic acid, C 9 H 14 0 21 is trimethyl-2.2. 3-cyclo-pentene-4-acid-i. Isolauronolic acid, C 9 H 14 0 2, is trimethyl-2.2.3-cyclo-pentene-3-acid-4.

Campholic acid, C 1 oH 18 0 2, is tetramethyl-1.2.2.3-cyclo-pentane acid-3. Camphononic acid, C9H1403, is trimethyl-2.2. 3-cyclo-pentanone-I-carboxylic acid-3. Camphorphorone, C 9 H 14 0, is methyl-21sobuty-lene-5-cyclo-pentanone-I. Isothujone, C10H160, is dimethyl-I. 2-isopropyl-3-cyclo-pentene-I-one-5. (F. W. Semmler, Ber., 1900, 33, p. 275.) L. Bouveault and G. Blanc (Comptes rendus, 1903, 136, p. 1460), prepared hydrocarbons of the cyclo-pentane series from cyclo- hexane compounds by the exhaustive methylation process of A. W. Hofmann (see Pyridine). For phenyl derivatives of the cyclo- pentane 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. 347 Cyclo-hexane Group. Hydrocarbons. - Cyclo-hexane, or hexahydro benzene, C 6 H 121 is obtained by the action of sodium on a boiling alcoholic solution of I. 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 I. 2.4. 5--tetrabrombenzene (N. Zelinsky, Ber., 1901, 34, p. 2803). It is stable towards halogens at ordinary temperature. Benzene hexachloride, C 6 H 6 C1 61 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 /3 form results by chlorinating boiling benzene in sunlight, and may be separated from the a variety by distillation in a current of steam. It sublimes at about 310° C. Similar varieties of benzene hexabromide are known.

Hexahydrocymene (methyl-i-isopropyl-4-cyclo-hexane), C10H20, is important since it is the parent substance of many terpenes (q.v.). It is obtained by the reduction of 1.4 dibrommenthane with sodium (J. de Montgolfier, Ann. chim. phys., 1880 [5], 19, p. 158), or of cymene, limonene, &c., by Sabatier and Senderens's method. It is a colourless liquid which boils at 180° C.

Cyclo-hexene (tetrahydrobenzene), C 6 H 10, 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-I, whilst potassium permanganate oxidizes it to cyclo-hexandi-ol.

Cyclo-hexadiene (dihydrobenzene), C 6 H 8. - Two isomers are possible, namely cyclo-hexadiene-i. 3 and cyclo-hexadiene-i4. A. v. Baeyer obtained what was probably a mixture of the two by heating I. 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 I.4-diamino-cyclo-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, CcHiiOH, 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 cyclo-hexanone. Quinite (cyclo-hexanediol-i 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-I. 3.5) is obtained by reducing an aqueous solution of phloroglucin with sodium (W. Wislicenus, Ber., 18 94, 2 7, P. 357). Quercite (cyclo-hexane-pentol-1.2. 3.4. 5), isolated from acorns i n 1849 by H. Braconnot (Ann. chim. phys. [3], 27, p. 39 2), crystallizes in colourless prisms which melt at 234° C. When heated in vacuo to 240° C. it yields hydroquinone, quinone and pyrogallol. It is dextro-rotatory. A laevo-form occurs in the leaves of Gymnema sylvestre (F. B. Power, Journ. Chem. Soc., 1904, 85, p. 624).

Inosite (cyclo-hexane-hexol), C 6 H 6 (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 pirate (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 /-form is also found as a methyl ether in quebrachite. By mixing the d- and 1- 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, C 6 H 10 0, 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, C H and a mixture of ketones (C. Mannul, Ber., 1907, 40, p. 153). Methyl-I-cyclo-hexanone-3, CH 3 C 5 H 9 0, 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, Comptes rendus, 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, 33 6, p. 2 99). It can be transformed into the isomeric methyl-I-cyclo-hexanone-2 (0. Wallach, Ann., 1904, 3 2 9, p. 368). For methyl-I-cyclo-hexanone-4, obtained by distilling y-methyl pimelate with lime, see 0. Wallach, Ber., 1906, 39, p. 1492.

Cyclo-hexane-dione-i3 (dihydroresorcin), C 6 H 8 O 2, was obtained by G. Merling (Ann., 1894, 278, p. 28) by reducing resorcin in hot alcoholic solution with sodium amalgam. Cyclo-hexane-dione-I. 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-hydroquinone. 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), C 6 H 2 O 6, 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-oxybenzene with alcohol (R. Nietzki, Ber., 1885, 18, pp. 513, 1838). Triquinoyl (hexaketo-cyclo-hexane) C 6 0 6.8H 2 O, 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).

CycIo-hexenones. - Two types of ketones are to be noted in this group, namely the a/3 and ,fay ketones, depending upon the position of the double linkage in the molecule, thus: H2C / CH2: CH CO HC? CHCH2 '> CO 'CH 2 CH 2 / NCH2CH2?

( a /I) (f?') These two classes show characteristic differences in properties. For example, on reduction with zinc and alcoholic potash, the a/' compounds give saturated ketones and also bi-molecular compounds, the Jay being unaffected; the Jay series react with hydroxylamine in a normal manner, the a/3 yield oxamino-oximes.

Methyl-i-cyclo-hexene- I-one-3, CH. C 6 H 7 0, is obtained by condensing sodium aceto-acetate with methylene iodide, the ester so formed being then hydrolysed. Isocamphorphorone, C 9 H 14 O, is trimethyl i. 6.6.-cyclo-hexene-i-one 6. Isocamphor, CioH160, is methyl-Iisopropyl-3-cyclo-hexene-I-one 6.

Acids

Hexahydrobenzoic acid, C 6 H 11 CO 2 I-I, is obtained by the reduction of benzoic acid, or by the condensation of 1.5 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, Journ.. Chem. Soc., 1905, 87, p. 90). The sulphochloride of the acid on reduction with tin and hydrochloric acid gives hexahydrothiophenol,. C 6 H 11 SH, a colourless oil which boils at 158-160° C. (W. Borsche,, Ber., 1906, 39, p. 392).

Quin i c acid, C 6 H 7 (OH) 4 CO 2 H (tetra -oxy.cyclohexane carboxylic acid), is found in coffee 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, C6Hio(C02H)2 (cyclo-hexanedicarboxylic acids). - Three acids of this group are known, containing the Carb-oxyl-groups in the 1.2, 1.3, and 1.4 positions, and each exists in two stereo-isomeric forms (cis- and trans-). The anhydride of the cis-I.2 acid, obtained by heating the anhydride of the trans-acid, forms prisms which melt at 192° C. When heated with hydrochloric acid it passes into the trans-variety. The racemic trans-acid is produced by the reduction of the dihydrobromide of A 4 -tetrahydrophthalic acid or dihydrophthalic acid. It is split into its active components by means of its quinine salt (A. Werner and H. E. Conrad, Ber., 18 99, 32, p. 3046). Hexahydroisophthalic acids (cyclo-hexane-i. 3dicarboxylic acids) are obtained by the action of methylene iodide on disodio-pentane tetracarboxylic ester (W. H. Perkin, Journ. Chem. Soc., 1891, 59, p. 79 8); by the action of trimethylene bromide on disodio-propane tetracarboxylic ester; and by the reduction of isophthalic acid with sodium amalgam, the tetrahydro acids first formed being converted into hydrobromides and further reduced (A. v. Baeyer and V. Villiger, Ann., 1893, 276, p. 255). The cisand trans- forms can be separated by means of their sodium salts. The trans-acid is a racemic compound, which on heating with acetyl chloride gives the anhydride of the cis-acid.

Hexahydroterephthalic acids (cyclo-hexane-I. 4-dicarboxvlic acids). These acids are obtained by the reduction of the hydrobromides of the diand tetra-hydroterephthalic acids or by the action of ethylene dibromide on disodio-butane tetracarboxylic acid. An important derivative is succino-succinic acid, C 6 H 6 0 2 (CO 2 H) 21 or cyclo-hexanedione-2.5-dicarboxylic acid-I. 4, which is obtained as its ester by the action of sodium or sodium ethylate on succinic ester (H. Fehling, Ann., 18 44, 49, p. 192; F.

Hermann, Ann., 1882, 211, p. 306).

It crystallizes in needles or prisms, and dissolves in alcohol to form a bright blue fluorescent liquid, which on the addition of ferric chloride becomes and A4 Tetraiiydro< cherry red. The acid on heating loses CO 2 and gives cyclo-hexanedione-I.4. Tetrahydro Tetrahydrobenzoic acid (cyclo-hexene i-carboxylic acid-I), C 6 H 9 CO 2 H. Three structural isomers are possible. The Hydrobromide A' acid results on boiling the A 2 acid on reduction with alkalis, or on eliminating hydroHEXAHYDRO bromic acid from i-brom-cyclo-hexane carboxylic acid-I. The 2 acid is formed on the reduction of benzoic acid with sodium amalgam. The A 3 acid is Sodium obtained by eliminating the elements of amalgam water from 4-oxy-cyclo-hexane-i-carb- p1.4 Dihydro oxylic acid (W. H. Perkin, jun., Journ. Chem. Soc., 1904, 85, p. 43 1). Shikimic acid (3.4.6-trioxy-ALtetrahydrobenzoic acid) is found in the fruit of Illicium religiosum. On fusion with alkalis it yields para-oxybenzoic acid, and nas cent hydrogen reduces it to hydro shikimic acid. Sedanolic acid, C12H2003, which is found along with sedanonic acid, C12H18031 in the higher boiling fractions of celery oil, is an orthooxyamyl-A 5 -tetrahydrobenzoic acid, sedanonic acid being orthovaleryl-A l -tetrahydrobenzoic acid (G. Ciamician and P. Silber, Ber., 18 97, 30, pp. 49 2, 501, 1419 seq.). Sedanolic acid readily decomposes into water and its lactone sedanolid, C 12 H 18 0 2, the odorous constituent of celery oil.

Tetrahydrophthalic acids (cyclo - hexene dicarboxylic acids), C 6 H 8 (CO 2 H) 2. Of the ortho-series four acids are known. The A' acid is obtained as its anhydride by heating the 2 acid to 220° C., or by distilling hydropyromellitic acid. Alkaline potassium permanganate oxidizes it to adipic acid. The A 2 acid is formed along with the A 4 acid by reducing phthalic acid with sodium amalgam in hot solutions. The A 4 acid exists in cis- and transforms. The trans-variety is produced by reducing phthalic acid, and the cis-acid by reducing 2.4 dihydrophthalic acid.

In the meta-series, four acids are also known. The A 2 acid is formed along with the A 4 (cis) acid by reducing isophthalic acid. The trans A 4 acid is formed by heating the cis-acid with hydrochloric acid under pressure. The A 3 acid is formed when the anhydride of tetrahydro rimesic acid is distilled (W. H. Perkin, junr., Journ. Chem. Soc., 1905, 8 7, p. 293).

In the para-series, three acids are known. The A' acid is formed by the direct reduction of terephthalic acid; by boiling the 2 acid with caustic soda; and by the reduction (in the heat) of A I. ' dihydroterephthalic acid. The 2 acid exists in cis- and trans- forms; these are produced simultaneously in the reduction of A or A 1.5 dihydroterephthalic acids by sodium amalgam.

There are five possible dihydrobenzoic acids. One was obtained in the form of its amide by the reduction of benzamide in alkaline solution with sodium amalgam (A. Hutchinson, Ber., 1891, 24, p. 177). The 1.3 acid is obtained on oxidizing dihydrobenzaldehyde with silver oxide or by the reduction of meta-trimethylaminobenzoic acid (R. Willstatter, Ber., 1904, 37, p. 1859).

Of the dihydrophthalic acids, five are known in the ortho-series, two of which are stereo-isomers of the cis- and trans-type, and a similar number are known in the para-series. The A l -' 4 acid is obtained as its anhydride by heating A 2.4 dihydrophthalic anhydride with acetic anhydride. When boiled with caustic soda it isomerizes to a mixture of the A 2.4 and A 2 '° dihydrophthalic acids. The acid is obtained by boiling the dihydrobromide of the A 2 '° acid with alcoholic potash or by continued boiling of the 2.6 acid with caustic soda.

The 2' acid is formed when phthalic acid is reduced in the cold by sodium amalgam or by heating the A 2 ' 4 and A 3 " acids with caustic soda. "The trans-modification of A35 acid is produced when phthalic acid is reduced by sodium amalgam in the presence of acetic acid. When heated for some time with acetic anhydride it changes to the cis-form. The trans-acid has been resolved by means of its strychnine salts into two optically active isomerides, both of which readily pass to 2' dihydrophthalic acid (A. Neville, Journ. Chem. Soc., 1906, 89, p. 1744).

Of the dihydroterephthalic acids, the A acid is obtained by heating the dibromide of the 2 tetrahydro acid with alcoholic potash. It cannot be prepared by a direct reduction of terephthalic acid. On warming with caustic soda it is converted into the A 1 ' 4 acid. The A i 4 acid is also obtained by the direct reduction of terephthalic acid. It is the most stable of the dihydro acids. The A 1.5 acid is obtained by boiling the cis- and trans-A 2.5 acids with water, which are obtained on reducing terephthalic acid with sodium amalgam in faintly alkaline solution. The relationships existing between the various hydrophthalic acids may be shown as follows: - Dihydro (Trans.) Acetic anhydride A 3.5 Dihydro (Cis.) A. Dihydro Anhydride with acetic anhydride Sodium amalgam in faintly alkaline solution Sodium amalgam (hot) .1 Hydrobromide on reduction Remove H Br from 1.3 Dihydro dibromide Cyclo-heptane Group. Cyclo-heptane (suberane), C 7 H 14, obtained by the reduction of suberyl iodide, is a liquid which boils at 117° C. On treatment with bromine in the presence of aluminium bromide it gives chiefly pentabromtoluene. When heated with hydriodic acid to 230° C. it gives methylhexamethylene. On oxidation with nitric acid (sp. gr. 1.4) it yields pimelic acid. Disuberyl, C 7 H 13. C 7 H 13, a thick oily liquid, boiling at 290-291° C., is obtained by the reduction of suberyl bromide.

Cyclo-heptene, C 7 H 121 is obtained by the action of alcoholic potash on suberyl iodide; and from cyclo-heptane carboxylic acid, the amide of which by the action of sodium hypobromite is converted into cyclo-heptanamine, which, in its turn, is destructively methylated (R. Willstatter, Ber., 1901, 34, 131). Cyclo-heptadiene 1.3, C7Hio, is obtained from cyclo-heptene (Willstatter, loc. cit.). It is identical' with the hydrotropilidine, which results by the destructive methylation of tropane.

Euterpene (trimethyl-i 4.4-cyclo-heptadiene 1.5), C 1 oH 1 s is prepared from dihydroeucarveol. By the action of hydrobromic acid (in glacial acetic acid solution) and reduction of the resulting product it yields I. 2-dimethyl-4-ethylbenzene (A. v. Baeyer, Ber., 1897,30, p. 2075). Cyclo-heptatriene (tropilidine), C 7 H 81 is formed on distilling tropine with baryta; and from cyclo-heptadiene by forming its addition product with bromine and heating this with quinoline to 150-160° C. (R. Willstatter, loc. cit.). Chromic acid oxidizes it to benzoic acid and benzaldehyde. With bromine it forms a dibromide, which then heated to 110° C. decomposes into hydrobromic acid and benzyl bromide.

Cyclo-heptanol, C,H 13 0H, is formed by the reduction of suberone, and by the action of silver nitrite on the hydrochloride of cyclo- hexanamine (N. Demjanow, Centralblatt, 1904, i. p. 1214). Cyclo-heptanone (suberone), C 7 H 12 O, is formed on the distillation of suberic acid with lime, and from a-brom-cyclo-heptane carboxylic acid by treatment with baryta and subsequent distillation over lead peroxide (R. Willstatter, Ber.. 1898, 31, p. 2507). It is a colourless liquid having a peppermint odour, and boiling at 178.5-179.5° C. Nitric acid oxidizes it to n-pimelic acid.

Sodium amalgam (hot) Sodium amalgam ± acetic acid Phthalic Acid Sodium amalgam (cold) Bo with Dihydro o Boil with water water 1'5 Dihydro Sodium amalgam Boil + NaOH Tetrahydro Dibromide -{- Reduce alcoholic potash D1HYDRO TEREPhthalic Acid Tropilene, C 7 H 10 0, is obtained in small quantities by the distillation of methyltropine methyl hydroxide, and by the hydrolysis of 13methyltropidine with dilute hydrochloric acid. It is an oily liquid, with an odour resembling that of benzaldehyde. It forms a benzal compound, and gives an oyxmethylene derivative and cannot be oxidized to an acid, reactions which point to it being a ketone containing the grouping -CH 2 CO-. It is thus to be regarded as a cyclo-heptenei-one-7. Cyclo-heptane carboxylic acid (suberanic acid), C7H13C02H, is obtained by the reduction of cyclo-heptene-I-carboxylic acid; from brom-cyclo-heptane by the Grignard reaction; and by the reduction of hydrotropilidine carboxylic acid by sodium in alcoholic solution (R. Willstatter, Ber., 1898, 31. p. 2504). The corresponding oxyacid is obtained by the hydrolysis of the nitrile, which is formed by the addition of hydrocyanic acid to suberone (A. Spiegel, Ann., 1882, 211, p. 117).

Four cyclo-heptene carboxylic acids are known. Cyclo-heptene-i- carboxylic acid-i is prepared from oxysuberanic acid. This acid when heated with concentrated hydrochloric acid to 120-130° C. yields a chlor-acid, which on warming with alcoholic potash is transformed into the cyclo-heptene compound. Cyclo-heptene-2-carboxylic acid-1 is formed by the reduction of cyclo-heptatriene 2.4. 6-carboxylic acid-1. On boiling with caustic soda it isomerizes to the corresponding I-acid.

Cyclo-heptatriene carboxylic acids, C 7 H 7 CO 2 H. All four are known. According to F. Buchner (Ber., 1898, 31, p. 2242) they may be represented as follows: The a-acid (a-isophenylacetic acid) is obtained by the hydrolysis of pseudophenylacetamide, formed by condensing diazoacetic ester with benzene, the resulting pseudophenyl acetic ester being then left in contact with strong ammonia for a long time. 13-Isophenylacetic acid is formed by strongly heating pseudophenylacetic ester in an air-free sealed tube and hydrolysing the resulting /-isophenylacetic ester. y-Isophenylacetic acid is obtained by heating the /3 and S acids for a long time with alcoholic potash (A. Einhorn, Ber., 1894, 27, p. 2828; E. Buchner, Ber., 1898, 31, p. 2249). 5-Isophenylacetic acid is obtained by heating the iodmethylate of anhydroecgonine ester with dilute caustic soda (A. Einhorn, Ber., 1893, 26, 3.329).

Numerous amino-derivatives of the cyclo-heptane series have been prepared by R. Willstatter in the course of his investigations on the constitution of tropine (q.v.). Amino-cyclo-heptane (suberylamine) is obtained by the reduction of suberone oxime or by the action of sodium hypobromite on the amide of cycloheptane carboxylic acid.

Cyclo-octane Group. Few members of this group are known. By the distillation of the calcium salt of azelaic acid H. Mayer (Ann., 18 93, 2 75, p. 363) obtained azelain ketone, C,H140, a liquid of peppermint odour. It boils at 90-91° C. (23 mm.) and is readily oxidized by potassium permanganate to oxysuberic acid. It is apparently cyclo-octanone (see also W. Miller and A. Tschitschkin, Centralblatt, 1899, 2., p. 181).

Pseudopelletierine (methyl granatonine), C9H15N0, an alkaloid of the pomegranate, is a derivative of cyclo-octane, and resembles tropine in that it contains a nitrogen bridge between two carbon atoms. It is an inactive base, and also has ketonic properties. On oxidation it yields methyl granatic ester, which, by the exhaustive methylation process, is converted into homopiperylene dicarboxylic ester, HO 2 C CH :CH CH 2 CH 2 CH :C. H CO 2 H, from which suberic acid may be obtained on reduction. When reduced in alcoholic solution by means of sodium amalgam it yields methyl granatoline, 08H130H NCH3; this substance, on oxidation with cold potassium permanganate, is converted into granatoline, C 8 H, 5 NO, which on distillation over zinc dust yields pyridine. Methyl granatoline on treatment with hydriodic acid and red phosphorus, followed by caustic potash, yields methyl granatinine, C 9 H 15 N, which when heated with hydriodic acid and phosphorus to 240° C. is converted into methyl granatanine, C 8 H 14 NCH 31 and granatanine, C 8 H 14 NH. The hydrochloride of the latter base when distilled over zinc dust yields a-propyl pyridine. By the electrolytic reduction of pseudopelletierine, N-methyl granatanine is obtained, and this by exhaustive methylation is converted into A O des-dimethyl granatanine. This latter compound readily forms an iodmethylate, which on treatment with silver oxide yields the corresponding ammonium hydroxide. The ammonium hydroxide on distillation decomposes into trimethylamine, water and cyclo-octadiene 1.3.

CH 2 CH-CH 2 CH2CH-CH 2 CH2-CH-CH2 CH 2 NMe CO --> CH 2 NMe CH 2 ->CH 2 HO NMe 2 CH 2 -> CH 3 CH-C11 2 CH2 CH-CHs C H2C H-CH2 Pseudopelletierine N-methyl granatanine CH 2 CH-CH, CH, - CH-CH, CH2CH:CH H2 NMe CH 2 4--CH 2 HO NMe 3 CH,4C H 2 CH H2 CH = CH CH 2 - CH =CH CH2CH2CH A - o des-methyl cyclo-octadiene granatanine Cyclo-octadiene, C8H12, as above prepared, is a strong-smelling oil which decolorizes potassium permanganate solution instantaneously. It readily polymerizes to a di-cyclo-octadiene and polymer (C8H12).

(R. Willstatter, Ber., 1905, 3 8, pp. 1 975, 1984; G. Ciamician and P. Silber, Ber., 1893, 26, p. 2750; A. Piccinini, Gazz., 1902, 32, I p. 260). ,6-cyclo-octadiene has been prepared from methyl granatinine iodmethylate.

Cyclo-octane, C 8 H, 6 is obtained by the reduction of the above unsaturated hydrocarbon by the Sabatier and Senderens's method. It is a liquid which boils at 146.3-148° C. and possesses a strong camphor odour. On oxidation it yields suberic acid (R. Willstatter, Ber., 1907, 40, pp. 957). 0. Doebner (Ber., 1902, 35, pp. 2129, 2 53 8; 1903, 3 6, p. 43 18) obtained compounds, which in all probability are cyclo-octadienes, by the distillation of s-vinylacrylic acid, sorbic acid, and cinnamenyl acrylic acid with anhydrous baryta.

Cyclo-nonane Group. According to N. Zelinsky (Ber., 1907, 40, p. 780) cyclononanone, C 9 H 16 O, a liquid boiling at 95-97° C., is formed on distilling sebacic acid with lime, and from this, by reduction to the corresponding secondary alcohol, conversion of the latter into the iodide, and subsequent reduction of this with zinc, cyclo-nonane, C 9 H 18, a liquid boiling at 170-172° C. is obtained.