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Give the preparation of alkane from the unsaturated hydrocarbons. |
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Answer» Solution :Defination of Hydrogenation : Dihydrogen GAS adds to alkenes and alkynes in the PRESENE of finely divided CATALYSTS like platinum, palladium or nickel to form alkanes. This process is called hydrogenation. * Work of catalyst : These metals absorb dihydrogen gas on their surfaces and ACTIVATE the hydrogen-hydrogen bond. Platinum and palladium catalyse the reaction at room temperature but relatively higher temperatureand pressure are required with nickel catalysts. * Some examples of hydrogenation reaction : When hydrogen is added to unsaturated hydrocarbons like alkene and alkyne and alkane is formed, such type of reaction is known as alkane. (i) `underset("Ethene")(CH_(2))=CH_(2)+H_(2)underset(or Ni, Delta)overset(Pt//Pd)rarrunderset("Ethane")(CH_(3))-CH_(3)` (ii) `underset("Propane")(CH_(3))-CH=CH_(2)+H_(2)underset(or Ni, Delta)overset(Pt//Pd)RARR underset("Propane")(CH_(3))-CH_(2)-CH_(3)` (iii) `underset("Propyne")(CH_(3))-C-=C-H+2H_(2)underset(or Ni, Delta)overset(Pt//Pd)rarrunderset("Propane")(CH_(3))-CH_(2)-CH_(3)` Note : Rany nickel is used as catalyst. It is a working nickel catalyst and used in the form of powder. |
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