Page:EB1911 - Volume 22.djvu/44

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): [CH₂·CH₂·CO₂]₂Ca⟶[CH₂·CH₂]₂CO; 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):—

by the action of sodium ethylate on δ-ketonic acids (D. Vorländer, Ber., 1895, 28, p. 2348):—

CH2	CH2·CH2	╲ CO2H⟶ CH2	CH2·CH2	CO;
	CO·CH2		CO·CH2

from sodio-malonic ester and αβ-unsaturated ketones or ketonic esters:—

(RO2C)2CH2+Ph·CH:CH·CO·CH3⟶PhCH	CH2———CO	CH2;
	CH(CO2R)·CO

from aceto-acetic ester and esters of αβ-unsaturated acids, followed by elimination of the carboxyl group:—

CH3·CO·CH2·CO2R+R′2C:CH·CO2R⟶CO	CH2·CR′2	CHCO2R;
	CH2·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):—

2CH3·CO·CH2·CO2R+OHC·R′⟶CH3·C	CH2·CHR′	CH2;
	CH·—CO

from 1·5-diketones which contain a methyl group next the keto-group (W. Kerp, Ann., 1896, 290, p. 123):—

3CH3·CO·CH3⟶(CH3)2C	CH2·C(CH3)	CH;
	CH2 — CO

by the condensation of succinic acid with sodium ethylate, followed by saponification and elimination of carbon dioxide:—

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):—

CO2R	＋CH2	CO2R	⟶	CO·CH2	CH2.
|				|
ĊO2R		CO2R		CO·CH2

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):—

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 α-halogen derivatives of unsaturated acids:—

CH3·CH:CBr·CO2R+NaCH(CO2R)2⟶CH3·CH	CH·CO2R
	|	;
	Ċ(CO2R)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·CO2R  N:N·CH·CO2R	⟶H2C	CHCO2R	;
CH2N2+	|| ⟶  ||
	C..H·CO2R H2C·CH·CO2R		CHCO2R

and by the Grignard reaction (S. Malmgren, Ber., 1903, 36, pp. 668, 2622; N. Zelinsky, ibid., 1902, 35, p. 2687).

Trimethylene, C₃H₆, 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, C₃H₅·CO₂H, is prepared by heating the 1.1-dicarboxylic acid; and by the hydrolysis of its nitrile, formed by heating γ-chlorbutyro-nitrile with potash (L. Henry and P. Dalle, Chem. Centralblatt, 1901, 1, 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 αβ-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 α-bromglutaric ester. It does not yield an anhydride.

Cyclo-butane, C₄H₈, was obtained by R. Willstätter (Bern, 1907, 40, 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 180–200° C. by the above method gives 𝑛-butane.

Cyclo-butene, C₄H₆, formed by distilling trimethyl-cyclo-butyl-ammonium 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 1.1-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, C₄H₇CO₂H. This basic acid yields a monobrom derivative which, by the action of aqueous potash, gives the corresponding hydroxy-cyclo-butane carboxylic acid, C₄H₆(OH)·CO₂H. 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, C₁₈H₁₆O₄, which result by the hydrolytic splitting of truxilline, C₃₈H₄₆N₂O₈, 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 α-acid on oxidation yields benzoic acid, whilst the β-acid yields benzil in addition. The α-acid is diphenyl-2.4-cyclo-butane dicarboxylic acid –1.3; and the β-acid diphenyl-3.4-cyclo-butane dicarboxylic acid –1.2. By alkalis they are transformed into stereo-isomers, the α-acid giving γ-truxillic acid, and the β-acid δ-truxillic acid. The α-acid was synthesized by C. N. Riiber (Ber., 1902, 35, p. 2411; 1904, 37, p. 2274), by oxidizing diphenyl-2.4-cyclo-butane-bismethylene malonic acid (from cinnamic aldehyde and malonic acid in the presence of quinoline) with potassium permanganate.

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·CO	CO
‖ |⟶	‖|⟶	‖
HO·C̈·C(OH) ⫶ C(OH)	HO·C̈·CO·CO	HO·C̈·CO
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., 1893, 275, p. 327). It is a colourless liquid which boils at 50–51° C. Methyl-cyclo-pentane, C₅H₉CH₃, 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, C₅H₈, a liquid obtained by the action of alcoholic potash on iodo-cyclo-pentane, boils at 45° C. Cyclo-pentadiene, C₅H₆, 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 ·CH2· group is very reactive and behaves in a similar manner to the grouping ·CO·CH₂·CO· in open chain compounds, e.g. with aldehydes and ketones it gives the