OLEFINE, in organic chemistry, the generic name given to open chain hydrocarbons having only singly and doubly linked pairs of carbon atoms. The word is derived from the French olefiant (from olefier, to make oil), which was the name given to ethylene, the first member of the series, by the Dutch chemists, J. R. Deiman, Paets van Troostwyk, N. Bondt and A. Lauwerenburgh in 1795. The simple olefines containing one doubly-linked pair of carbon atoms have the general formula (CnH2n; the di-olefines, containing two doubly-linked pairs, have the general formula CnH2n-2 and are consequently isomeric with the simple acetylenes. Tri-, tetra- and more complicated members are also known. The name of any particular member of the series is derived from that of the corresponding member of the paraffin series by removing the final syllable " -ane," and replacing it by the syllable " ylene." Isomerism in the olefine series does not appear untU the third member of the series is reached.
The higher olefines are found in the tar which is obtained by distilling bituminous shales, in illuminating gas, and among the products formed by distilling paraffin under pressure (T. E. Thorpe and J. Young, Ann., 1873, 165, p. 1). The olefines may be synthetically prepared by eliminating water from the alcohols of the general formula CnH2n+1.OH, using sulphuric acid or zinc chloride generally as the dehydrating agent, although phosphorus pentoxide, syrupy phosphoric acid and anhydrous oxalic acid may frequently be substituted. In this method of preparation it is found that the secondary alcohols decompose more readily that the primary alcohols of the series, and when sulphuric acid is used, two phases are present in the reaction, the first being the building up of an intermediate sulphuric acid ester, which then decomposes into sulphuric acid and hydrocarbon: C2H5OH → C2H5.HSO4 → C2H4.H2SO4. As an alternative to the above method, V. Ipatiew (Ber., 1901, 34, p. 596 et seq.) has shown that the alcohols break up into ethylenes and water when their vapour is passed through a heated tube containing some " contact " substance, such as graphite, kieselguhr, etc. (see also J. B. Senderens, Comptes rendus, 1907, 144, pp. 382, 1109).
They may also be prepared by eliminating the halogen hydride from the alkyl halides by heating with alcoholic potash, or with litharge at 220° C. (A. Eltekow, Ber., 1878, 11, p. 414); by the action of metals on the halogen compounds CH2Br2; by boiling the aqueous solution of nitrites of the primary amines (V. Meyer, Ber., 1876, 9, p. 543), C3H7NHj+HN02 = N2+2H2O-l-C3H6;_by the electrolysis of the alkali salts of saturated dicarboxylic acids; by the decomposition of /3-haloid fatty acids with sodium carbonate, CH3CHBrCH(CH3)-C02H =C02 + HBr + CH3CH iCH-CHs; by distilling the barium salts of acids CH2n-202 with sodium methylate in vacuo (I. Mai, Ber., 1889, 22, p. 2135); from the higher alcohols by converting them into esters which are then distilled (F. Krafft, Ber., 1883, 16, p. 3018): Ci6H33CH2-CH2-OH->Ci6H33CH2-CH2-0'CO-R^ CeHssCH : CH2-I-R-C00H ; from tertiary alcohols by the action of acetic anhydride in the presence of a small quantity of sulphuric acid (L. Henry, Comptes rendus, 1907, 144, p. 552): (CH3)2-C(OH)-CH(CH3)2^(CH3)2C:C(CH3)2+CH2:C(CH3)-CH _ (CH,)2; from unsaturated alcohols by the action of metal-ammonium compounds (E. Chablay, Comptes rendus, 1906, 143, p. 123): 2CH2:CH-CH2OH-|-2NH3Na = CH2:CH-CH3+CH2;CH-CH2ONa -|-NaOH-|-2NH3; from the lower members of the series by heating them with alkyl halides in the presence of lead oxide or lime: C5Hio-t-2CH3l =2HI + C7H14; and by the action of the zinc alkyls upon the halogen substituted olefines.
A. Mailhe (Chem. Zeit., 1906, 30, p. 37) has shown that on passing the monohalogen derivatives of the paraffins through a glass tube containing reduced nickel, copper or cobalt at 250° C, olefines are produced, together with the halogen acids, and recombination is prevented by passing the gases through a solution of potash. The reaction probably proceeds thus: MCU-l-CnHjn+iCl-^HCl-l- Cl-M-CH2Cl^MCl2-i-CH2n, since the haloid derivatives of the monovalent metals do not act similarly. The anhydrous chlorides of nickel, cobalt, cadmium, barium, iron and lead act in the same way as catalysts at about 300° C, and the bromides of lead, cadmium, nickel and barium at about 320° C.
In their physical properties, the olefines resemble the normal paraffins, the lower members of the series being inflammable gases, the members from Cs to Cu liquids insoluble in water, and from ds upwards of solids. The chief normal members of the series are shown in the table.
Butylene Amylene Hexylene Heptylene .
Octylene Decylene .
Duodecylene CH2:CH2 CH3CH:CH2 C2Hs-CH:CH2 C3H7-CH:CH2 C4H8CH:CH2 C6Hi,CH:CH2 CeHisCH :CH2 C8HCH:CH^ C9H19CH :CH2 ^-ioH2iCH :CH2 -169° -31° -102-7° (757 mm.) -50-2° (749 mm.) -5° 39°-40° 68° - 70° 122° - 123° 172° 84° (18 mm.)
96° (15 mm.)
In chemical properties, however, they differ very markedly from the paraffins. As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least) ; and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W. Markownikow, Ann., 1870, 153, p. 256).
They combine with hypochlorous acid to form chlorhydrins; and are easily soluble in concentrated sulphuric acid, giving rise to sulphuric acid esters; consequently if the solution be boiled with water, the alcohol from which the olefine was in the first place derived is regenerated. The oxides of nitrogen convert them into nitrosites and nitrosates (O. Wallach, Ann., 1887, 241, p. 288, etc.; J. Schmidt, Ber., 1902, 35, pp. 2323 et seq.). They also combine with nitrosyl bromide and chloride, and with many metallic haloid salts (platinum bichloride, Iridium chloride), with mercury salts (see K. A. Hofmann and J. Sand, Ber., 1900, 33, pp. 1340 et seq.), and those with a tertiary carbon atom yield double salts with zinc chloride. Dilute potassium permanganate oxidizes the olefines to glycols (G. Wagner, Ber., 1888, 21, p. 3359). With ozone they form ozonides (C. Harries, Ber., 1904, 37, p. 839). The higher members of the series readily polymerize in the presence of dilute sulphuric acid, zinc chloride, etc.
For the first member of the series see Ethylene.
Propylene, C3H6, may be obtained by passing the vapour of trimethylene through a heated tube (S. M. Tanatar, Ber., 1899, 32, pp. 702, 1965). It is a colourless gas which may be liquefied by a pressure of 7 to 8 atmospheres. Butylene, C4H8, exists in three isomeric forms: normal butylene, 'C2Hs-CH :CH2; pseudo-butylene, CH3-CH :CH-CH3; and isobutylene, (CH3)2C : CH2. Normal butylene is a readily condensible gas. Two spatial modifications of pseudobutylene, CH3-CH:CH-CH3,are known, the cis and the trans; they are prepared by heating the sodium salts of hydro-iodo-tiglic and hydro-iodo-angelic acids respectively (J. Wislicenus, Ann., 1900, 313, p. 228). Isobutylene, (CH3)2C:CH2, is formed in the dry distillation of fats, and also occurs among the products obtained when the vapour of fusel oil is led through a heated tube. It is a gas at ordinary temperature, and may be liquefied, the liquid boiling at -5° C. It combines with acetyl chloride in the presence of zinc chloride to form a ketone, which on warming breaks down into hydrochloric acid and mesityl oxide (I. L. Kondakow, Jour. Russ. pliys. chem. Soc. 26, p. 12). It polymerizes, giving isodibutylene, CsHie, and isotributylene, Ci2H24, Hquids which boil at 110-113° and 178-181° C. Amylene, CsHio, exists in five isomeric forms, viz. (n) propylethylene, CHs-CHo-CHj-CH :CH2; isopropylethylene, (CH3)2CH-CH : CH2; symmetrical methy 1-et hyl-ethy lene, CHs- CH : CH ( C2H6; unsymmetrical methyl-ethyl-ethylene, (CH3)(C2H6)C:CH2; and trimethyl ethylene, (CH3)2C: CH(CH3). The highest members of the series as yet known are cerotene, Cs6H62, which is obtained by the distillation of Chinese wax and is a paraffinlike solid which melts at 57° C, and melene, C3oH6c(?), which is obtained by the distillation of bees'-wax. It melts at 62° C. (B. J. Brodie, Ann., 1848, 67, p. 210; 1849, 71, p. 156).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)