Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/568

Rh 556 CHEMISTRY [ORGANIC. I. HYDROCARBONS. Starting with the saturated compounds of the C B H 2B+2 r;eries, the isologous series C B H 2B, CH 2w _ 2 , ........... C,,H 2 _ 32 are known. First Series, C B H 2B+2. Marsh Gas or Paraffin Series. The first member of the series is CH 4 (marsh gas or methane), and the homologues down to C 16 H 34 (hexdecane) have been obtained. The names and formulae will be given later on. General Properties. The members of the series exhibit a regular gradation in physical properties with each suc cessive addition of CH 2. Thus, the first four members are gaseous at ordinary temperatures, while the succeeding terms are liquids of increasing specific gravity and viscidity as the series is ascended ; those containing 20 or more carbon atoms are solid crystalline bodies. The boiling- point increases as the series is ascended, the difference between the boiling-points of the successive terms of the normal series decreasing regularly by about 4 C. as far as C 19 H 26, after which there appears to be a constant differ ence of 19 C. The paraffins are chemically distinguished for their in difference, hence the name applied to the series (parum affinis}. Being saturated molecules, they are incapable of uniting directly with any other element or radicle. The halogen elements produce by their action on paraffins substitution derivatives (haloid ethers), in which the hydro gen of the hydrocarbon is replaced by the halogen. CH 4, CH 3 C1 , CH 2 C1 2 , CHC1 3 , CC1 4 ; C^Hg &amp;gt; ^2&quot;s^ C/ 2 H 4 C1 2 , C 2 H 3 C1 3 , C 2 H 2 C1 4 , CC1 C 2 HC1 5 , 26 , &c., &c. These compounds will be again referred to under the family of the haloid ethers. Sulphuric acid is without action on paraffins, and at ordinary temperatures they are scarcely attacked by oxidizing agents ; but on heating with these agents they are either entirely oxidized to CO 2 and OH 2 , or, in addition, to acids of the acetic (C n H 2n+1 COOH) and succinic [C B H 2B ,(COOH) 2 ] series. Nitric acid exerts no action in the cold, but the concentrated acid attacks the higher members of the series when heated with them, forming nitro-substitution compounds in which hydrogen is replaced by nitryl (NO 2 ), and, in some instances, acids of the acetic and succinic series and nitriles. The lower members of the series are not acted on by nitric acid, but their nitro-derivatives can be obtained by indirect methods, the general method of preparation being the action of silver nitrite on the iodo-paraffin : C n H 2n+1 T + AgN0 2 = C B H 2n+1 (N0 2 ) + Agl. These nitre-paraffins are interesting as being metameric with the corresponding ethereal salts of nitrous acid; thus H ( JT?,, is metameric with methyl nitrite, ] Nitroethane, C ethyl nitrite, L 2n+l Generally C n H are metameric with O=N=O 6 N=O Nitro-parafflns. Ethereal nitrites. In accordance with the above formulation the two classes .of compounds are differently acted on by nascent hydrogen. ^-tl-On-l-l C B H 2n _f.j , = 2OH 2 + | 2n+1 N0 2 Nltro-paraffln. NH 2 Amine, or amido-paraffin. CH 2B+1 O NO Ethereal nitrite. C.H 2 OH Ammonia. Alcohol. The higher members of the series are resolved by pro longed heating in sealed tubes into members lower in the series and members of the isologous series, C B H 2B (defines), in accordance with the general equation Occurrence of Paraffins. Methane, or marsh gas, is an invariable product of the decomposition of organic matter excluded from the air, and is thus produced at the bottom of stagnant ponds, marshes, &c. This gas is the &quot; fire damp &quot; of coal mines ; it is found in volcanic gases, and the gas issuing from a mud volcano in the Crimea is almost pure methane. The normal paraffins are found in coal formations and other bituminous strata. Thus, Ameri can petroleum contains a mixture of all the paraffins from marsh gas to pentadecane (C ]5 H 32 ), or even higher mem bers. In boring for rock oil large quantities of methane escape, and from the freshly drawn petroleum ethane and propane are given off as gases at the ordinary temperature of the air. On distilling off the liquid portion (known commercially as &quot; paraffin oil &quot;) the higher members of the series remain as white crystalline solids. Many paraffins occur also in the oil obtained by the destructive distillation of Boghead and cannel coal. Solid paraffins are likewise formed in the destructive distillation of wood, coal, bitu minous shale, &c., and are found native, as fossil wax t ozokerite, hatchetin, &c. General Methods of Formation of Paraffitis. 1. By the action of nascent hydrogen upon haloid ethers of CnHn radicles s 0,^^+, + Hffa ; (Ha being used to represent a halogen). 2. By the action of zinc and water upon the iodides of CnHjn+j radicles 2C n H 2n+1 I + 2Zn + 20H, = Zn(HO) 2 + ZnI 2 + 2C n H 2n+!! . 3. By the action of water upon the organo-metallic bodies of the general formula Zn(C n H 2n + 1 ) 2 Zn(C B H SB+1 ) a + 20H 2 = Zn(HO) 2 + 2C n H sn+2. 4. By heating iodides of C n H 2n+1 radicles with zinc Zn + 2C n H 2n+1 I = ZnI 2 + C 2n H&amp;lt; n+2. In this reaction the paraffin is, at the same time, resolved into a lower member of the series containing half the number of carbon atoms, and the corresponding isologue of the CnH 2 n series C 2 nH 4n -|_ 2 = CnHjn+s + C n H 2n. 5. By the action of sodium on the iodides of C n H sn +! radicles 2C n H jn+1 I + Na 2 = C 2n H, B+3 + 2NaI. 6. By the electrolysis of the fatty acids of the series C n H jn O, (see ascetic series) 2C n H 2n O !! - 2C0 2 + C 2n _ 8 H 4n _, + H 2 7. By heating the dry sodium salts of C n H 2n .f j. COOH and C n H an .(COOH) 2 acids with sodium hydroxide CH,n+!. COONa + NaHO = Na 2 C0 3 + C n H 2n+J C n H 2n (COONa) 2 + 2NaHO = 2Na 2 C0 3 + C n H 2, l+2. 8. By the dry distillation of acetates and butyrates several par affins are formed. 9. Almost all organic compounds yield paraffins when heated in sealed tubes to a very high temperature with excess of strong hydriodic acid. 10. Many paraffins have been obtained by acting on a mixture of the corresponding iodides and ethyl alcohol with copper-coated zinc foil (Gladstone and Tribe s &quot;copper-zinc couple&quot;) C M H 2n+1 I + C 2 H 5 .OH + Zn = ZnI(C 2 H 5 0) + CnH^+j. Formulation and Classification of Paraffins. All the members of the paraffin series can be regarded as methane, in which one atom of hydrogen is replaced by C n H 2n+1 radicles ; thus