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Polymethylenes

POLYMETHYLENES, in chemistry, cyclic compounds, the simplest members of which are saturated hydrocarbons of general formula C.Hjn, where n may be i to 9, and known as tri-, tetra-, penta-, hexa-, and hepta-methylene, etc., or cyclopropane, -butane, -pentane, -hexane, -heptane, etc.:

f TT /"""U f"*U /~*LJ /~*11 f"*U f^U /i_n 2 , v,ri 2 > ^rij /i^ri 2 'V,ri 2 /v-n 2 '\~ri2v 2X .[ II CH< I | CH< >CH 2 ,etc.

\CH 2 , CH 2 C-H 2 \CH 2 -CH 2 , \CH 2 -CH^ Cyc/o-propane, -butane, -pentane, -hexane.

The unsaturated members of the series are named on the Geneva system in which the termination -one is replaced by-ene, -diene, -Iriene, according to the number of double linkages in the compound, the position of such double linkages being shown by a numeral immediately following the suffix -ene; for example I. is methyl-cyc/o-hexadiene i. 3. An alternative method employs A. v. Baeyer's symbol A. Thus A 2-4 indicates the presence of two double bonds in the molecule situated immediately after the carbon atoms 2 and 4; for example II. is A 2-4 dihydrophthalic acid.

C(CO.H):CH (6) (5)

As to the stability of these compounds, most trimethylene derivatives are comparatively unstable, the ring being broken fairly readily; the tetramethylene derivatives are rather more stable and the penta- and hexa-methylene compounds are very stable, showing little tendency to form open chain compounds under ordinary conditions (see CHEMISTRY: Organic).

Isomerism. No isomerism can occur in the monosubstitution derivatives but ordinary position isomerism exists in the diand poly-substitution compounds. Stereo-isomerism may occur: the simplest examples are the dibasic acids, where a. cis(maleinoid) form and a trans- (fumaroid) form have been observed. These isomers may frequently be distinguished by the facts that the 's-acids yield anhydrides more readily than the trans-acids, and are generally converted into the trans-adds on heating with hydrochloric acid. O. Aschan (Ber., 1902, 35, p. 3389) depicts these cases by representing the plane of the carbon atoms of the ring as a straight line and denoting the substituted hydrogen atoms by the letters X, Y, Z. Thus for dicarboxylic acids (C0 2 H = X) the possibilities are represented by .A. .A. / \ -A. /, \ X / (cis), JT (trans), jj (I).

The trans compound is perfectly asymmetric and so its mirror image (I) should exist, and, as all the trans compounds synthetically prepared are optically inactive, they are presumably racemic compounds (see O. Aschan, Chemie der alicyklischen Verbindungen, p. 346 seq.).

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):

CH2-CH 2 -Br , ... ,vr p , CHz-CHz. CH r CH 2 -Br+ 2Na - 2NaBr +CH r CH 2 ! 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 rettdus, 1901, 132, p. 210 seq.); and from hydrazines of the type CnHm-i-NH-NH* 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. 1899, 32, p. 3332): C n H 2n _ I ONa->C B H 2n _,O-CS.SNa(R) >C n H2n-2+COS+R-SH; or simply by dehydrating with anhydrous oxalic acid (N. Zelinsky, Ber., 1901, 34, p. 3249); and by eliminating the halogen acid from mono- or 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. '/.); by the reduction of cyclic esters with 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., 1893, 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, 2475):

CH 2 -CH 2 -CH 2 -CO 2 R CH 2 -CH 2 -CH 2 .

CH 2 -CH 2 -CO 2 R ~*CH 2 -CH 2 C-O ' by the action of sodium ethylate on 5-ketonic acids (D. Vorlander, Ber., 1895, 28, p. 2348):

/CH 2 -CH 2 v X xCH 2 -CH 2 \ CH< >CO; X CO-CH 3 \CO-CH 2 ' from sodio-malonic ester and a|3-unsaturated ketones or ketonic esters:

/CH 2 CO V (R0 2 C) 2 CH 2 +Ph-CH :CH-CO-CH3-PhCH< >CH 2 ; \CH(C0 2 R)-CO/ from aceto-acetic ester and esters of a|3-unsaturated acids, followed by elimination of the carboxyl group:

>CHCO 2 R ; / 2CH 8 -CO-CH 2 -CO 2 R+OHC-R'- CH,; CH 3 -CO-CH 2 -CO 2 R+R' 2 C:CH-CO 2 R-CO< \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) :

J "'\ : co from i-s-diketones which contain a methyl group next the keto-group (W. Kerp, Ann., 1896, 290, p. 123):

/CH 2 -C(CH 3 k 3 CH,-CO-CH S -(CH 3 ) 2 C< >CH; X CH 2 CO/ by the condensation of succinic acid with sodium ethylate, followed by saponification and elimination of carbon dioxide:

CH 2 -CH 2 -CO ^CO-CH.i-CHz 1 and from the condensation of ethyl oxalate with esters of other dibasic acids in presence of sodium ethylate (W. Dieckmann, Ber., 1897, 30, p. 1470; 1899, 32, p. 1933): C 2 R ___ /CO 2 R CO-CH* 2C 2 H 4 (C0 2 H) 2 -v +CH 2 > COjR N C0 2 R CO- 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. 194):

C 2 H 1 Br 2 +2NaCH(C0 2 R) 2 ->(CH 2 ) 2 C(C0 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-C0 2 R CH 3 -CH : CBr-CO 2 R+NaCH(CO2R)2-CH 3 -CH/ . | \C(C0 2 R) 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 cyclopropane series (E. Buchner, Ber., 1890, 23, p. 703; Ann., 1895, 284, p. 212; H. v. Pechmann, Ber., 1894, 27, p. 1891):

CH-CO 2 R N:N-CH-CO 2 R X CHC0 2 R CH 2 N 2 + II -> 1 I ->H 2 C< ' ; CH-CO 2 R H 2 C CH-CO 2 R \CHCO 2 R and by the Grignard reaction (S. Malmgren, Ber., 1903, 36, pp. 668, 2(122; N. Zelinsky, ibid., 1902, 35, p. 2687).

Cydo-propane Group.

Trimethylene, C 3 H 6 , 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 w-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 H5-CO 2 H, is prepared by heating the i.i-dicarboxylic acid; and by the hydrolysis of its nitrile, formed by heating -y-chlorbutyro-nitrilewith potash (L. Henry and P. Dalle, Chem. Centralblatt, 1901, I, p. 1357; 1902, I, p. 913). .It is a colourless oil, moderately soluble in water.

The I.I dicarboxylic acid is prepared from ethylene dibromide and sodio-malonic ester. The ring is split by sulphuric or hydrobromic acids. The cis 1 .2-cydo-propane dicarboxylic acid is formed by eliminating carbon dioxide from cyc/0-propane tricarboxylic acid -1.2.3 (from a/3-dibrompropionic ester and sodio-malonic ester). The trans-acid is produced on heating pyrazolin-4.5-dicarbpxylic ester, or by the action of alcoholic potash on a-bromglutaric ester. It does not yield an anhydride.

Cydo-butane Group.

Cydo-butane, C 4 H 8 , was obtained by R. Willstatter (Ber., 1907, 40, p. 3979) by the reduction of cyclobutene by the Sabatier and Senderens method. It is a colourless liquid which boils at 1 1-12 C., and its vapour burns with a luminous flame. Reduction at 1 80- 200 C. by the above method gives n-butane.

Cydo-butene, CiH 6 , formed by distilling trimethyl-cyc/o- 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 i.i-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 cycfo-butane carboxylic acid, C4H 7 CO 2 H. This basic acid yields a monobrom derivative which, by the action of aqueous potash, gives the corresponding hydroxycyc/o-butane carboxylic acid, C4H 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 cyc/o-butanone (keto-tetramethylene) is probably formed.

The truxillic acids, CisHieO^ which result by the hydrolytic splitting of truxilline, Cs8HN 2 O s , are phenyl derivatives of cyc/o-butane. Their constitution was determined by C. Liebermann (Ber., 1 888, 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 /3-acid yields benzil in addition. The a-acid is diphenyl-2.4-cyc/o-butane dicarboxylic acid -1.3; and the 0-acid diphenyl-34-cyclo-butane dicarboxylic acid -1.2. By alkalis they are transformed into stereo-isomers, the a-acid giving -y-truxillic acid, and the j3-acid 6-truxillic acid. The a-acid was synthesized by C. N. Riiber (Ber., 1902, 35, p. 2411; 1904, 37, p. 2274), by oxidizing diphenyl-2.4-cyc/o-butane- bismethylene malonic acid (fron cinnamic aldehyde and malonic acid in the presence of quinoline) with potassium permanganate.

Cydo-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 :

HO-C-C(OH) : C(OH) HO-C-CO-CO HO-C-Ca .. I - .- !- A >CO HO-C-C(OH) i C(OH) HO-C-CO-CO HO-C-CO/ Hexa-oxybenzene. Rhodizonic acid. Croconic acid. Cyclo-pentane, C 6 Hio, is obtained from rycfo-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., 1893, 275, p. 327). It is a colourless liquid which boils at 50-51 C. Methyl-cydo-pentane, CsHgCHs, 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. Cydo-pentene, C 6 H 8 , a liquid obtained by the action of alcoholic potash on iodo-cycto-pentane, boils at 45 C. Cyclopentadiene, CeHe, is found in the first runnings from crude benzene distillations. It is a liquid which boils at 41 C. It rapidly polymerizes to di-cyc/o-pentadiene. The -CH 2 - group is very reactive and behaves in a similar manner to the grouping -CO-CH 2 -CO- in open chain compounds, e.g. with aldehydes and ketones it gives the fulvcnes, substances characterized by their intense orange-red colour HC:CH (J. Thiele, Ber., 1900, 33, p. 669). Phenylfulven, \ >C:CHPh, HC-.CH 7 obtained from benzaldehyde and cyc/o-pentadiene, forms dark red plates. Diphenylfulven, from benzophenone and cyc/o-pentadienc, 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.

Cydo-pentanone, CsH s O, first prepared pure by the distillation of calcium adipate (J. Wislicenus, Ann., 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 cyc/o-pentanol, CsH 9 OH.

Croconic acid (dioxy-eyc/0-pentene-trione), C 6 H 2 O 6 , 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 cyc/o-pentane-pentanone (leuconic acid).

Derivatives of the cyc/o-pentane group are met with in the breaking-down products of the terpenes &..).

Campholactone, C 9 H] 4 O 2 , is the lactone of trimethyl-2-2-3-cyc/o- pentanol-5-carboxylic acid-3. For an isomer, isocampholactone (the lactone of trimethyl-2-2-3-eyc/o-pentanol-3-carboxylic acid-i) see W. H. Perkin, jun., Proc. Ghent. Soc., 1903, 19, p. 61. Lauronolic acid, C,H M O 2 , is trimethyl-2-2-3-cyc/o-pentene-4-acid-i. Isolauronolic acid, C 9 HuO 2 , is trimethyl-2-2-3-cyc/o-pentene-3-acid-4.

Campholic acid, CioHi 8 O 2 , is tetrametnyl-i-2-2-3-cyc/o-pentane acid-3. Camphononic acid, C 9 Hi4O 3 , is trimethyl-2-2-3-cyc/0- pentanone- 1 -carboxylic acid-3. Camphorphorone, C 9 HuO, is methyl-2- isobuty-lene-5-cycfo-pentanone-l. Isothujone, Ci Hi 6 O, is dimethyl-i-2-isopropyl-3-cyc/o-pentene-l-one-5. (F. W. Semmler, Ber., I9o, 33, p. 275.)

L. Bouveault and G. Blanc (Comptes rendus, 1903, 136, p. 1460), prepared hydrocarbons of the eyc/o-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. in; 315, p. 219 seq.; 1903, 326, p. 347.

Cydo-hexane Group.

Hydrocarbons. Cydo-hexane, or hexahydro benzene, C 6 Hi 2 , 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, CtH 6 Cl s , 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 o 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-cyc/o-hexane), CioH 20 , is important since it is the parent substance of many terpenes (<?..). It is obtained by the reduction of I -4 dibrommenthane with sodium (J. de Montgolfier, Ann. chim. phys., 1880 [5], 19, p. 158), or of cymene, limonene, etc., by Sabatier and Senderens's method. It is a colourless liquid which boils at 180 C.

Cydo-hexene (tetrahydrobenzene), CH 10 , was obtained by A. v. Baeyer by removing the elements of hydriodic acid from iodocydo-hexane on boiling it with quinoline. It is a liquid which boils at 82 C. Hypochlorous acid converts it into 2-chlor-cyc/o-hexanol-i, whilst potassium permanganate oxidizes it to cycfc-hexandi-ol.

Cydo-hexadiene (dihydrobenzene), CH 8 . Two isomers are possible, namely cyc/o-hexadiene-i-3 and cyc/o-hexadiene-l-4. A. v. Baeyer obtained what was probably a mixture of the two by heating 1-4 dibrom-cycfo-hexane with quinoline. C. Harries (Ann., and oxalic acids. The 1-4 compound also boils at 81-82 C. and on oxidation gives succinic and malonic acids.

Alcohols. Cydo-hexanol, C 6 H n OH, 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 cyc/o-hexanone. Quinite (cycJo-hexanediol- 1 -4) is prepared by reducing the corresponding ketone with sodium amalgam, cis-, and /rani-modifications being obtained which may be separated by their acetyl derivatives. Phlorogluctte (cyc/o-hexane-triol-l-3-s) is obtained by reducing an aqueous solution of phloroglucin with sodium (W. Wislicenus, Ber., 1894, 27, p. 357). ' Quercite (cydo-hexane-pentol-i-2-3'4-5), isolated from acorns in 1849 by H. Braconnot (Ann. chim. phys. [3], 27, p. 392), crystallizes in colourless prisms which melt at 234 C. When heated in vacua 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 (cyc/o-hexane-hexol), C 6 H 6 (OH),. 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 iromMateza 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 /- 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. Cydo-hexanone, CH 10 O, 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, Cu>H 2<1 and a mixture of ketones (C. Mannul, Ber., 1907,40, p. 153). Methyl-i-cydo-hexanone-^, CHj-CH 9 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, 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, 336, p. 299). It can be transformed into the isomeric methyl-i-cydo-hexanone-2 (O. Wallach, Ann., 1904, 329, p. 368). For methyl-i-cydo-hexanone-4, obtained by distilling y-methyl pimelate with lime, see O. Wallach, Ber., 1906, 39, p. 1492.

Cydo-hexane-dione-l-3 (dihydroresorcin), CH 8 2 , was obtained by G. Merling (Ann., 1894, 278, p. 28) by reducing resorcin in hot alcoholic solution with sodium amalgam. Cydo-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-hydroquinone. Cyclohexane-trione-i-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 pxypentaketo-cycfo-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 (hexaketp-cyc/o-hexane) CeOe - 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-cydo-pentene-trione) .

Cydo-hexenones. Two types of ketones are to be noted in this group, namely the o/3 and jS-y ketones, depending upon the position of the double linkage in the molecule, thus:

.CH 2 :CH ,CH-CH, V H 2 C< \CO HCf >CO N:H 2 -CH,/ N:H 2 -CH/ These two classes show characteristic differences in properties. For example, on reduction with zinc and alcoholic potash, the off compounds give saturated ketones and also bi-molecular compounds, the /S? being unaffected; the 0-y series react with hydroxylamine in a normal manner, the aft yield oxamino-oximes.

Melhyl-i-cydo-hexene-i-one-z, CHj-CjHvO, is obtained by condensing sodium aceto-acetate with methylene iodide, the ester so formed being then hydrolysed. Isocamphorphorone, C 9 HuO, is trimethyl i-6-6.-cyc/o-hexene-i-one 6. Isocamphor, Ci Hi 6 O, is methyl-l- isopropyl-3-cyc/o-hexene-i-one 6.

Acids. Hexahydrobenzoic acid, CHn'CO 2 H, is obtained by the reduction of benzole 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, CHnSH, a colourless oil which boils at 158-160 C. (W. Borsche, Ber., 1906, 39, p. 392).

Quinic acid, CH 7 (OH)4CO 2 H (tetra-oxy-cyc/o-hexane 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, CHio(CO s H) 2 (cyc/o-hexanedicarboxylic acids). Three acids of this group are known, containing the Carboxyl-groups in the 1-2, 1-3, and 1-4 positions, and each exists in two tereo-isomeric forms (CM- and trans-). The anhydride of theciVi-2 A2 and A* TETRAHYDRO^- ' I Heat A 1 TETEAHYDRO Hydrobromidf OH reduction 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 /rani-variety. The racemic trans-acid is produced by the reduction of the dihydrobromide of A 4 -tetrahydrophthalic acid or A 2 ' 6 dihydrophthalic acid. It is split into its active components by means of its quinine salt (A. Werner and H. E. Conrad, Ber., *899, 32, p. 3046). Hexahydroisophtholic acids (cyc/o-hexane-l'3- dicarboxylic acids) are obtained by the action of methylene iodide on disodio-pentane tetracarboxylic ester (W. H. Perkin, Journ. Chem. Soc., 1891, 59, p. 798); 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 (rani-acid is a racemic compound, which on heating with acetyl chloride gives the anhydride of the cii-acid.

Hexahydroterephthalic acids (cydo-hexane-l-4-dicarboxylic acids). These acids are obtained by the reduction of the hydrobromides of the di- and 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 O2(CO 2 H)2, or cyc/o- hexanedione-2>5-dicarboxylic acid-1'4, which is obtained as its ester by the action of sodium or sodium ethylate on succinic ester (H. Fehling, Ann., 1844, 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 cherry red. The acid on heating loses COa and gives cye/o-hexanedione-1'4.

Tetrahydrobenzoic acid (cyc/o- hexeneI -carboxy lie acid- 1 ) , C 6 H 9 - COjH . Three structural isomers are possible. The A 1 acid results on boiling the A 2 acid with alkalis, or on eliminating hydrobromic acid from i-brom-cyc/o- hexanecarboxylic acid- 1. The A 2 acid is formed on the reduction of benzoic acid with sodium amalgam. The A 3 acid is obtained by eliminating the elements of water from 4-oxy-cyc/o-hexane-i- carboxylic acid (W. H. Perkin, iun., Journ. Chem. Soc., 1904, 85, p. 431). Shikimic acid (3-4'6-trioxy-A 1 -tetrahydrobenzoic acid) is found in the fruit of Illicium religiosum. On fusion with alkalis it yields para-oxybenzoic acid, and nascent hydrogen reduces it to hydroshikimicacid. Sedanolic acid, CiaH^Os, which is found along with sedanonic acid, C^HigOa, in the higher boiling fractions of celery oil, is an ortho- oxyamyl-A 6 -tetrahydrobenzoic acid, sedanonic acid being orthovaleryl-A'-tetrahydrobenzoic acid(G. Ciamician and P. Silber, Ber., 1897, 30, pp. 492, 501, 1419 seq.). Sedanolic acid readily decomposes into water and its lactone sedanolid, Ci2Hi 8 O 2 , the odorous constituent of celery oil.

Telrahydrophthalic acids (cycfo-hexene dicarboxylic acids), C 6 H S (CO2H)2. Of the ortho-series four acids are known. The A 1 acid is obtained as its anhydride by heating the A 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 /raws-variety is produced by reducing phthalic acid, and the cis-acid by reducing A 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 m-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, 87, p. 293).

In the para-series, three acids are known. The A 1 acid is formed by the direct reduction of terephthalic acid; by boiling the A 2 acid with caustic soda; and by the reduction (in the heat) of A 1 ' 4 dihydroterephthalic acid. The A 2 acid exists in cis- and trans- forms; these are produced simultaneously in the reduction of A 1 '* or A 1 ' 6 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 A 1 '* 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 knbwn in the para-series. The A 1 ' 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 ' s dihydrophthalic acids. The A 2 ' 4 acid is obtained by boiling the dihydrobromide of the A 2 ' 6 acid with alcoholic potash or by continued boiling of the A 2 ' 6 acid with caustic soda.

The A 2 ' 6 acid is formed when phthalic acid is reduced in the cold by sodium amalgam or by heating the A 2 ' 4 and A 3 ' 5 acids with caustic soda. The (raws- modification of A 3 ' 5 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-iorm. The trans-acid has been resolved by means of its strychnine salts into two optically active isomerides, both of which readily pass to A 2 ' 6 dihydrophthalic acid (A. Neville, Journ. Chem. Soc., 1906, 89, p. 1744).

Of the dihydroterephthalic acids, the A 1 ' 3 acid is obtained by heating the dibromide of the A 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. TheA 1 ' 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- andirons-A 2 ' 6 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:

Sodium amalgam (hot) Sodium amalgam + acetic acid PHTHALIC ACID Sodium Sodium amalgam (cold)

amalgam (hot)

A 2-6 DIHYDRO Alkali Eydrobromide with alcoholic potash A3-5 DIHYDRO (TRANS.)

J, Acetic anhydride A3-5 DIHYDRO (cis.)

A 2 ' 4 DIHYDRO Anhydride with acetic anhydride Isetttmm amalgam Sodium amalgam in faintly alkaline solution Sodium Boil with I A2-6 DlHYDRO amalgam (hot)

water ( A 1-5 DlflYDRO Sodium amalgam -. , Kan A 2 TETRAHYDRO- >A 1 TETRAHYDRO Reduce Dibromide 4- alcoholic potash Remove H Br from Hydrobromifc on reduction dibromide -HEXAHYDRO Cyclo-heptane Croup.

Cyclo-heptane (suberane), C 7 Hi 4 , 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.

acid thick _ _ reduction of suberyl bromide.

Cyc\o-heptene, C^Hu, is obtained by the action of alcoholic potash on suberyl iodide; and from eyc/o-heptane carboxylic acid, the amide of which by the action of sodium hypobromite is converted into cyc/o-heptanamine, which, in its turn, is destructively methylated (R. Willstatter, Ber., 1901, 34, 131). Cyclo-heptadiene 1-3, C 7 H 10 , is obtained from cyc/o-heptene (Willstatter, loc. cit.). It is identical with the hydrotropilidine, which results by the destructive methylation of tropane.

Euterpene (trimethyl-i-4-4-cyc/o-heptadiene I -5), CioHie is prepared from dihydroeucarveol. By the action of hydrobromic acid (in glacial acetic acid solution) and reduction of the resulting product it yields l-2-dimethyl-4-ethylbenzene (A. v. Baeyer, Ber., 1897, 30, p. 2075). Cyc\o-heptatriene (tropilidine), C 7 H 8 , is formed on distilling tropine with baryta; and from cyc/o-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 IIO C. decomposes into hydrobromic acid and benzyl bromide, Cyclo-heptanol, CiHupH, is formed by the reduction of suberone, and by the action of silver nitrite on the hydrochloride of cyclohexanamine (N. Demjanow, Centralblatt, 1904, i. p. 1214).

Cyc\o-heptanone (suberone), CyH^O, is formed on the distillation of suberic acid with lime, and from o-brom-cyc/o-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 I78'5-I79'5 C. Nitric acid oxidizes it to n-pimelic acid.

Tropilene, CjHioO, is obtained in small quantities by the distillation of a-methyltropine methyl hydroxide, and by the hydrolysis of 0- im-thyltropidine 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,-CO-. It is thus to be regarded as a cyc/o-heptene-i-one-7.

Cyc\o-heptane carboxylic acid (suberanic acid), CrHuCOjH, is obtained by the reduction of cyc/o-heptene-i-carboxylic acid; from brom-cyc/o-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 cyo-heptene carboxylic acids are known. Cyc\o-heptene-i- carboxylic acid-l 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 cye/o-heptene compound. Cyc\o~heptene-2-carboxylic acid-l is formed by the reduction of cyc/o-heptatriene 2-4-6- carboxylic acid-l. On boiling with caustic soda it isomerizes to the corresponding l-acid.

Cyc\o-heptatriene carboxylic acids, CiHjCOtH. All four are known. According to F. Buchner (Ber., 1898, 31, p. 2242) they may be represented as follows :

aiWorji.

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. 0-Isophenylacetic acid is formed by strongly heating pseudophenylacetic ester in an air-free sealed tube and hydrolysing the resulting 0-isophenyIacetic ester. y-Isophenylacetic acid is obtained by heating the and & acids for a long time with alcoholic potash (A. Einhorn, Ber., 1894, 27, p. 2828; E. Buchner, Ber., 1898, 31, p. 2249). d- Isophenylacetic acid is obtained by heating the iodmethylate of anhydroecgonine ester with dilute caustic soda (A. Einhorn, Ber., 1893, 26, P- 329).

Numerous ammo-derivatives of the cyclo-heptane series have been prepared by R. Willstatter in the course of his investigations on the constitution of tropine (g.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.

Cyc\o-octane Croup.

Few members of this group are known. By the distillation of the calcium salt of azelaic acid H. Mayer (Ann., 1893, 275, p. 363) obtained azelain ketone, C 8 H U O, 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 cyc/o-octanone (see also W. Miller and A. Tschitschkin, Centralblatt, 1899, 2., p. 181).

Pseudopelletierine (methyl granatonine), C 8 Hi 6 NO, an alkaloid of the pomegranate, is a derivative of cyc/o-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 homopipcrylene dicarboxvlic ester, HO,C-CH:CH CH, CH a CH:CH-CO S H, from which suberic acid may be obtained on reduction. When reduced in alcoholic solution by means of sodium amalgam it yields methyl granatoline, CsHnOH-NCHj; this substance, on oxidation with cold potassium permanganate, is converted into granatoline, C 8 HuNO, which on listillation over zinc dust yields pyridine. Methyl granatoline on treatment with hydriodic acid and red phosphorus, followed by caustic potash, yields methyl granatinine, C9Hi 6 N, which when heated with hydriodic acid and phosphorus to 240 C. is converted into methyl granatanine, C 8 H U .NCH3, and granatanine, C 8 H U NH. The hydrochloride of the latter base when distilled over zinc dust yields o-propyl pyridine. By the electrolytic reduction of pseudopelleticrine, W-methyl granatanine is obtained, and this by exhaustive methylation is converted into A Mes-dimethyl granatanine. This Uter 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 cyc/o-octadiene I -3.

CH.CH CH, CH.NMe CO - CH.CH CH, Pseudopelletierine CH 2 CH CH, >CH,NMe CH, CH.-CH CH, JV-methyl granatanine CH, CH CH, -CH,HO NMe,CH, CH, CH CH, CH.CH CH, CH, CH CH, CH,CH:CH CH, NMe CH,<-CH,HO NMe,CH^-CH, CH CH,CH = CH CH, CH = CH CH, CH, CH A- 4 <i-methyl cyc/o-octadiene granatanine Cyclo-octadiene, CHi,, as above prepared, is a strong-smelling oil which decolorizes potassium permanganate solution instantaneously. It readily polymerizes to a di-eyc/o-octadiene and polymer (CgHuJ. (R. Willstatter, Ber., 1905, 38, pp. 1975, 1984; G. Ciamician and P. Silber, Ber., 1893, 26, p. 2750; A. Piccinini, Cazz., 1902, 32, I p. 260). P-cyclo-octadicne has been prepared from methyl granatinine iodmethylate.

Cycle-octane, CH, 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). O. Doebner (Ber., 1902, 35, pp. 2129, 2 .538; 1903, 36, p. 4318) obtained compounds, which in all probability are cyc/o-octadienes, by the distillation of /3-vinylacrylic acid, sorbic acid, and cinnamenyl acrylic acid with anhydrous baryta.

Cyclo-nowone Croup.

According to N. Zelinsky (Ber., 1907, 40, p. 780) cyclononanone, CjHi.O, a liquid boiling at 95797 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, CH [8 , a liquid boiling at 170-172 C. is obtained.

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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