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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