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Shweta Thakur posted an Question

July 04, 2020 • 04:13 am

30 points

IIT JAM
Chemistry (CY)

Addition of hydrogen to alkyl halide is based on adsorption mechanism ????

addition of hydrogen to alkyl halide is based on adsorption mechanism ????

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Priyanshu kumar

shweta, alkyl halides can't directly reduced to alkane by H2/pd rather alkyl halide first undegoes dehydrohalogenation and forms alkene then alkene adds with H2(hydrogenation reaction) by metal catalyst Ni,Pd or Pt...so direct alkyl halides can't adds to hydrogen...see my above explanation
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sir how it first undergoes dehydrohalogenation ..as . there is no any strong base
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yes that why..alkyl halide directly it doesnt add...
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I did'nt get
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wait the question is alkyl halide react with hydrogen in presence of zn /hcl
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shweta alkyl halide reduces to alkane in presence of Zn and dilute hcl
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Zinc is basically a catalyst in this reaction the Hydrogen molecules get deposited on zinc’s top most layer forming zinc hydride(ZnH2) it’s called chemical adsorption This ZnH2 reacts with The alkyl halide let’s say CH3Cl(methyl chloride) and thus we obtain Methane and Zinc chloride This process is much faster than just simply using H2 To conclude the reactions go this way Zn +H2 -> ZnH2 ZnH2 + 2CH3Cl -> ZnCl2 +2CH4
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read this shweta
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Dinesh khalmaniya 1

hope this will help you 🙏
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Dinesh khalmaniya 1

yes, shweta. Alkyl halides can also be reduced catalytically to alkane by H2/Pd or LiAIH4 or by H2/Ni. The yields are generally high and the hydrocarbons formed are pure. reduction by Ni/H2 provide surface for the reaction. so it is adsorption reaction. reaction will be such like reduction of alkene by Ni /H2. check the mechanism
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sir In presence of zn /hcl also this is only the mechanism
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alkene react with hydrogen in presence of zn/HCl
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this is the question
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Priyanshu kumar

The reaction is heterogeneous catalysis or surface catalysis as metal catalyst provide a surface for binding..
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Priyanshu kumar Best Answer

see this for reference
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Priyanshu kumar

shweta addition of Hydrogen(H2) to alkene ,reaction is called hydrogenation and this reaction is adsorption reaction....as the metal catalysts used here is Ni,Pd and Pt which provides a catalytic surface to binding the reactants at their surface
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and H2 doesn't adds to alkyl halide
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ok sir it add to catalyst first right?
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alkyl halide....dehydrohalogenation occurs...alkene forms and then H2 hydrogenation
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