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3., METHODS OF PREPARATION OF ALKANES, (a) By Wurtz Reaction, When a solution of an alkyl halide in ether solvent is treated with sodium metal two alkyl groups combine, together. Yields of products are best for primary (-60%) halides and poorest for tertiary halides (-3%)., 2Na, 2CH,I, CH,CH, + 2Nal, ether, Ethyl iodide, Ethane, CH,, CCH-Br, CH,, CH - CH, CH,, CH,, 2Na, + 2NaBr, CH,, ether, CH, 2-bromo propane, 2-3- dimethyl butane, This method is suitable for the preparation of symmetrical alkanes. A mixture of products is obtained if two, different alkyl halides are reacted. Methane cannot be prepared by this method., (b) By Reduction of Halides, P, CH, + HI, Ethane, +H,, Zn/Cu, CH, + HI, + 2H, CH,OH, Ethane, C,H,, Ethyl, lodide, CH, + HI, Ethane, + 2H ZNHC, + HI, Red P, C,H, +,, Éthane, (c), From Alkyl Halides through Grignard Reagents, Dry, CH,CH,Br + Mg, CH,CH,MgBr, Hydroyes, C,H, + Mg(OH)Br, ether, Ethyl bromide, Ethyl magnesium, bromide, Ethane, Hydroxy, magnesium bromide, In these reactions, the alkyl group of alkyl magnesium halide gets converted into alkane., Corey-House Synthesis, (d), R-X+ 2LI - RLI + LIX, 2R - Li + CuX R-CULI + LIX, R, Lithium dialkyl copper, R., R-CULI+R'X R-R'+ RCu + LIX, Alkane, Unlike Wurtz reaction, this reactions can be employed to prepare unsymmetrical alkanes., Page # 2