Page 1 - Lesson notes

SUBJECT-CHEMISTRY

CHAPTER-HALOALKANES AND HALOARENES.

KEY NOTES:

Method so preparation of haloalkanes:
(a) From alcohol.
ZnCl
R OH NX  R X H O




2
2



R OH NaBr H SO  R Br NaHSO  H O


4
2
4
2


R OH PX  R X H PO


3 3 3


R OH PCl  R Cl POCl  HCl


5
3
RedP/X
R OH R X


2
[X 2 Br ,I ] 2 2
R OH SOCl  R Cl SO   HCl




2 2
(b) From hydrocarbons:
(i)By free radical halogenations of alkanes:

Cl
2 .uvlight
CH CH CH CH  CH CH CH CH Cl CH CH CHClCH
3
2
2
2
2
2
2
3
3
3
5
orheat
(ii) from alkene:



R.CH CH  H X  R CH CH

Markonikov's

2
3
rule
X |




benzoyl peroxides
R CH CH  H Br  R CH CH  Br
2
2
2
antimarkonikov's rule

(c) Halide exchange:
R X NaI  R I NaX (X = Cl, Br) [finkelstain reaction]




dry acetone
Agf orHg


R X  R F [swarts rection]
2 2 F or CoF or SbF
3
2
Chemical properties:
(i) Nucleophilic substitution: