Chemical properties
Halogenation:- CH 4 + Cl 2
UV
CH 3 Cl + HCl
UV UV
CH
UV 3 Cl CH 2 Cl 2 CHCl 3 CCl 4
Noted:- Iodination is a reversible reaction. So it is carried out by heating alkane in the presence of some oxidizing agent like iodic acid( HIO3) or nitric acid( HNO3) or mercuric oxide( HgO) which oxidizes HI formed during the reaction.
CH 4 + I 2
CH 3 I + HI 5HI + HIO 3 3H 2 O + 3I 2
2HI + 2HNO 3 2H 2 O + I 2 + 2NO 2 Noted:- Fluorination of alkane takes place explosively resulting even in the rupture of C— C bond in higher alkanes. Features of Halogenations:-
( i) The reactivity of Halogens:- F2 > Cl2 > Br2 > I2.( ii) The rate of replacement of Hydrogens of alkanes is:
CH3CH2CH2CH3 n- Butane
Cl2
hv
3 ° > 2 ° > 1 °
CH3CH2CH2CH2Cl + CH3CH2CHCH3 Cl
°
1
° °
CH3C
CH3
3 1 Cl2 Cl
° CH- CH3
1
CH3
CH3 CH3
h 36 %( 3 °)
CH3
Isobutane CH3
CH- CH2 Cl 64 %( 1 °)