Oxidation with Ozone:- Ozonolysis – give carbonyls compounds
O
O3 CH3CH2CH CCH3 CH 3CH 2CH C
CH3 O
Zn / H O
2
CH3CH2CH + CH3CCH3 + Zn( OH) 2
O
CH3
O O Ozonide
CH3
Noted:- Bromine water test and Baeyer’ s test are used to detect the presence of double bond while ozonolysis is used to detect the position of double bond.
Alkynes Unsaturated hydrocarbon which have triple bond. General molecular formula CnH2n – 2 sp hybridization Shows chain, positional and functional isomerism � �
Preparation:- From vicinal dihalides:- dehalogenation
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2KOH( alc) CH3 C CH + 2KBr + 2H2O
Chemical Properties:- Addition Reaction:- Alkyne show electrophilic addition reaction. Addition of Hydrogen:- Hydrogenation.
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CH3C Propyne
CH + 2H2
Ni CH3CH2CH3
Noted:- It may be noted that the hydrogenation can be controlled at the alkene stage only. This is possible by using a Lindlar’ s catalysts or sodium in liquid NH3 at 200k temp.
Noted:- It may be again noted that the catalytic reduction of alkynes in the presence of Lindlar’ s catalyst gives cis-alkenes while in the presence of sodium in liquid NH3( Birch reduction) gives trans-alkenes. �
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