- Chlorination of methane:
- At the outset, the only compounds that are present in the mixture are chlorine
and methane ⇒ the only reaction that can take place is the one that produces
chloromethane and hydrogen chloride.
- At the outset, the only compounds that are present in the mixture are chlorine
HCHHHHCHH- Cl (^2) orheat light Cl + H Cl
- As the reaction progresses, the concentration of chloromethane in the mixture
increases and a second substitution reaction begins to occur ⇒ Chloromethane
reacts with chlorine to produce dichloromethane.
HC
H
H
Cl
Cl
Cl 2 HCCl Cl
H
- orheat light + H
- The dichloromethane produced can then react to form trichloromethane.
- The trichloromethane, as it accumulates in the mixture, can react to produce
tetrachloromethane.
- Chlorination of most of higher alkanes gives a mixture of isomeric monochloro
products as well as more highly halogenated compounds.
- Chlorine is relatively unselective ⇒ it does not discriminate greatly among the
different types of hydrogen atoms (1°, 2°, and 3°) in an alkane.
CH 3 CHCH (^3) light
Cl 2
Cl Cl
Cl
CH 3
CH 3 CHCH 2
CH 3
CH 3 CHCH 3
CH 3
- +polychlorinated+H
products
Isobutane Isobutyl chloridetert-Buty chloride (23%)
(48%) (29%)
- Alkane chlorinations usually give a complex mixture of products ⇒ they are not
generally useful synthetic methods for the preparation of a specific alkyl chloride.