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PARAFFIN

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Originally appearing in Volume V20, Page 756 of the 1911 Encyclopedia Britannica.
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PARAFFIN , in See also:

chemistry, the generic name given to the hydro-carbons of the See also:general See also:formula CnH2a+2. Many of these See also:hydrocarbons exist as naturally occurring products, the See also:lower (gaseous) members of the See also:series being met with as exhalations from decaying organic See also:matter, or issuing from fissures in the See also:earth; and the higher members of the series occur in See also:petroleum (chiefly See also:American) and See also:ozokerite. They may be synthetized by reducing the alkyl halides (preferably the iodides) with nascent See also:hydrogen, using either See also:sodium See also:amalgam, See also:zinc and hydrochloric See also:acid, concentrated hydriodic acid (See also:Berthelot, Jour. prak. Chem. 1868, 104, p. 103), See also:aluminium amalgam (H. See also:Wislicenus, ibid., 1896 (2), S4) or the zinc-See also:copper couple (J. H. See also:Gladstone and A. Tribe, Ber., 1873, 6, p. 202 seq.) as reducing agents. They may also be derived from alkyl halides by See also:heating to I20'140' with aluminium chloride in the proportion of three molecules of alkyl halide to one See also:molecule of aluminium chloride (B.

KOhnlein, Ber., 1883, 16, p. 56o) ; by heating with zinc and See also:

water to 150—16o° C. (E. See also:Frank-See also:land, See also:Ann., 1849, 71, p. 203; 185o, 74, p. 41), 2 RI+2Zn+2H20= 2RH+ZnI2+Zn(OH)2; by See also:conversion into zinc alkyls, which are then decomposed by water, ZnR2+2H2O=2 RH+Zn(OH)2; by conversion into the Grignard reagent with metallic See also:magnesium and decomposition of this either by water, dilute acids or preferably ammonium chloride (J. Houben, Ber., 1905, 38, p. 3019), RMgI+ See also:H2O = RH + MgI (OH) ; by the See also:action of See also:potassium hydride (H. See also:Moissan, Comptes rendus, 1902, 134, p. 389) ; and by the action % 3.0 39.0 18.0 I0.0 30.0 of sodium, in See also:absolute See also:ether See also:solution (A. See also:Wurtz, Ann. chim. phys., t855 (3), 44, P. 275), 2RI+2Na=R•R+2NaI.

They may also be obtained by the reduction of the higher fatty acids with hydriodic acid (F. See also:

Krafft, Ber., 1882, 15, pp. 1687, 1711), CnH2,~O,+6HI= CnH2n.See also:F2+2H2O+312; by the conversion of See also:ketones into ketone chlorides by the action of See also:phosphorus pentachloride, these being then reduced by hydriodic acid, (CnH2„-F1)2 CO—> (CnH2,,.{.1)2C C12—i' (C„H2,,.i.i)2CH2; by the reduction of unsaturated hydrocarbons with hydrogen in the presence of a " contact " substance, such, for example, as reduced See also:nickel, copper, See also:iron or See also:cobalt (P. See also:Sabatier and J. B. Senderens, Ann. chim. phys., 1905 [8], 4, pp. 319, 433) ; by the elimination of See also:carbon dioxide from the fatty acids on heating their salts with soda-See also:lime or baryta, CH3CO2Na+NaOH=See also:CH4+Na2CO,, or by heating their See also:barium salts with sodium methylate in vacuo (I. See also:Mai, Ber., 1889, 22, p. 2133) ; by the See also:electrolysis of the fatty acids (H. See also:Kolbe, Ann., 1849, 69, p. 257), 2C2H402=See also:C2H6+2CO2+H2O; and by the action of the zinc alkyls on the ketone chlorides, (See also:CH3)2CC12+ Zn(See also:CH2)2 = C5H12+ZnC12. The See also:principal members of the series are shown in the following table: Name.

Formula. Melting- Boiling- Melting- point. point. Methane CH4 -184° — 164° (76o mm.) Ethane C2116 -172.1 ° — 84.1 ° (749 ,, ) Propane See also:

C3H6 -45° -4~•5° Normal Butane C4Hio — +1 Isobutane „ — -17° Normal Pentane . C51112 — +36.3° Secondary Pentane — +30.4° See also:Tertiary Pentane — +9° Hexane C6H14 — +69° Heptane C7H16 — 98—99° Octane C,H,8 — 125—126° Nonane C,H2o -51° 15o° Decane C,oH22 -31° 173—4° Undecane C11H24 -26.5° 196° Dodecane C12H26 -12° 214—216° Tridecane C12Hz6 -6.2° 234° Tetradecane C,4H30 +4° 252° Pentadecane C16H32 +lo° 270° Hexadecane C161133 +18° 287° Heptadecane C171136 +22° 170° (15 mm.) Octadecane C16H66 +28° 317° Nonadecane C19H40 +32° 330° Eicosane C20Ha2 +37° 205° (15 mm.) Heneicosane C211-13.1 +4o° 215° („ ) Docosane C22H+6 +44° 224° Tricosane C25H 48 +48° 234° („ ) Tetracosane C24H,o +51° 243° ( ) Hexacosane C26H94 +58° — Hentriacontane C,1H6e +68° 302° (15 mm.) Dotriacontane C22H66 +70.5° 331° („ ) Pentatriacontane Ca6H72 +75° 331° l ) Dimyricyl CeoHl22 +102° — lowest members of the series are gases at See also:ordinary temperature; those of carbon content C6 to C15 are colourless liquids, and the higher members from C19 onwards are crystalline solids. The highest members only volatilize without decomposition when distilled under diminished pressure. They are not soluble in water, although the lower and See also:middle members of the series are readily soluble in See also:alcohol and ether, the solubility, however, decreasing with increase of molecular See also:weight, so that the highest members of the series are almost insoluble in these solvents. The specific gravity increases with the molecular weight but always remains below that of water: The paraffins are characterized by their See also:great inertness towards most chemical reagents. Fuming sulphuric acid converts the middle and higher members of the series into sulphonic acids and dissolves the lower members (R. A. Worstall, Amer. Chem.

Journ., 1898, 20, p. 664). Dilute nitric acid, when heated with the paraffins in a See also:

tube, converts them into secondary and tertiary nitro-derivatives (M. Konowalow, Ber., 1895, z8, p. 1852), whilst See also:long boiling with strong nitric acid or nitro-sulphuric acid converts the middle and higher members of the series partly into See also:primary mono- and di-nitro compounds and partly oxidizes them to carbonic, acetic, oxalic and succinic acids (Worstall, ibid., 20, p. 202; 21, p. 211). Fuming nitric acid only reacts slowly with the normal paraffins at ordinary temperature, but with those containing a tertiary carbon See also:atom the reactionis very energetic, oxidation products (fatty acids and dibasic acids) and a small quantity of polynitro compounds are obtained (W. Markownikow, Cenlralblatt, 1899, I, p. 1064; Ber., 1899, 32, p. 1441). See also:Chlorine reacts with the paraffins, readily substituting hydrogen.

Isomeric hydrocarbons in this series first appear with butane, the number increasing rapidly as the complexity of the molecule increases. For a means of deter-See also:

mining the number of isomers see E. See also:Cayley, Ber., 1875, 8, p.Io56; F. See also:Hermann, Ber., 1898, 31, p. 91. For Methane see See also:MARSH See also:GAS. Ethane, C2H6, occurs in crude petroleum. It may be prepared by the general methods given above; by heating See also:mercury See also:ethyl with concentrated sulphuric acid (C. Schorlemmer, Ann., 1864, 132, p. 234) ; or by heating acetic anhydride with barium peroxide (P Schtitzenberger, Zeit. Chemie, 1865, p. 703), 2(CH2CO)2O+BaO2=C2H6+Ba(See also:C2H,02)2+2CO2.

It is a colourless gas which can be liquefied at 4° C. by a pressure of 46 atmospheres. By slow See also:

combustion it yields first water and acetaldehyde, which then oxidizes to oxides of carbon and water (W. A. See also:Bone; see See also:FLAME), whilst in ozonized See also:air at too° it gives ethyl alcohol, together with acetaldehyde and traces of formaldehyde (Bone, Proc. Chem. See also:Soc., 1904, 29, p. 127). Dimyricyl (hexacontane), C60H122, is prepared by fusing myric l iodide with sodium (C. See also:Hell and C. Hagele, Ber., 1889, 22, p. 502). It is only very slightly soluble in alcohol and ether.

End of Article: PARAFFIN

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