This video lecture from Aliphatic Hydrocarbons (F.Sc. second year Chemistry) covers the preparation of Alkenes (Part 2). Vicinal Dihalides (with two halide groups on adjacent carbon atoms) when reacted with zinc in an alcohol like methanol or ethanol yield alkenes and zinc reacts with halogens and a pi bon appears between adjacent carbon atoms. Kolbe’s electrolysis is also discussed in case of Dicarboxylic acid (with two –COOH groups on adjacent carbon atoms like succinic acid). Their salts of sodium or potassium are taken for electrolysis. In present situation removal of carbon dioxide at anode (Decarboxylation) leaves two adjacent carbon atoms with un shared electron giving rise to a pi bond and hence an alkene. Partial hydrogenation of alkynes is also discussed which yields cis- and trans- alkene products in the presence of poisoned palladium in quinoline (Lindler’s catalyst) or sodium dissolved in ammonia at low temperatures. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.