This document discusses alkenyl halides, specifically vinyl chloride and allyl chloride. It provides methods of preparation of vinyl chloride from acetylene and of allyl chloride from propylene. It also describes the chemical reactions of vinyl chloride and allyl chloride with aqueous and alcoholic KOH. Allyl chloride is more reactive than vinyl chloride due to the percentage of s-character in the C-Cl bond, stabilization of the allyl carbocation by resonance, and double bond character in the C-Cl bond of vinyl chloride.

1. 1
B.Sc. First year
Students
Semester – II
Unit-III A) Alkenyl Halides
by
Dr Pramod R Padole

2. 2

4. Organic Chemisrtry
Unit-III
A) Alkenyl Halides:
B) Aryl Halides:
C) Alcohols:

5. III A) Alkenyl Halides:
Synthesis
of
allyl
chloride
from
propylene
Synthesis
of
vinyl
chloride
from
acetylene
1 2 3 4
Comparison
of
Reactivity
of vinyl &
allyl
chloride
Reactions
of both
with
aqueous
&
alcoholic
KOH

6. III B) Aryl Halides:
First
Synthesis Chlorobenzene
from benzene, phenol and
benzene diazonium chloride
Second
Synthesis of Benzyl chloride
from toluene and benzyl
alcohol
Third
Reactions of both with aqueous
KOH, NH3 and sodium ethoxide,
Comparison of reactivity of
chlorobenzene and benzyl chloride.
Fourth Benzyne intermediate
mechanism

7. 3. Trihydric alcohols: Glycerol:
Preparation from propylene,
Chemical Reactions with Na, HCl, PCl5 , HNO3 and KHSO4.
2. Chemical Reactions:
with Na, PCl5 , CH3COOH, ZnCl2 , conc. H2SO4 and
dehydration with heat
1. Dihydric alcohols:
Ethylene glycol- Preparation from ethylene,
ethylene chloride and ethylene oxide,
4. Pinacol- pinacolone rearrangement
(mechanism).
C) Alcohols:

8. LOGO
Unit-III
A) Alkenyl Halides:

9. III A) Alkenyl Halides:
Preparation
of
allyl
chloride
from
propylene
Preparation
of
vinyl
chloride
from
acetylene
1 2 3 4
Comparison
of
Reactivity
of vinyl &
allyl
chloride
Reactions
of both
with
aqueous
&
alcoholic
KOH

10. Unit-III A) Alkenyl Halides:
 Halogen derivatives of an alkanes are formed by replacing
one or more hydrogen atoms of an alkane with same number
of halogen atoms like chlorine, bromine or iodine.
 On the basis of number of halogen atoms present in a
molecule they are classified as:
a) Monohalogen, b) Dihalogen, c) Trihalogen,
d) Tetrahalogen derivatives, etc.
 Monohalogen derivatives of an alkanes are also called as
an alkyl halides.
 e.g. R-CH2-X ( X = Cl, Br, I)
Alkyl halide
Q.1) Ethyl bromide is a ____________ . (W-16, ½ Mark)
(a) Primary alkyl halide (b) Secondary alkyl halide
(c) Tertiary alkyl halide (d) None of these

11. Unit-III A) Alkenyl Halides:
 Monohalogen derivatives of an
alkenes are called alkenyl halides.
e.g. R-CH=CH-X ( X = Cl, Br, I)
Alkenyl halide
Where,
R- may be –H or any alkyl group.

12. By Dr Pramod R Padole
Unit-III A) Alkenyl Halides:
Study
of
Vinyl Chloride
(CH2=CH-Cl):
Alkenyl
Halides
Study
of
Allyl Chloride
(CH2=CH-CH2-Cl):

13. Study of
Vinyl Chloride (CH2=CH-Cl):
:
Q.1) In vinyl chloride, the state of hybridization of carbon attached to chlorine atom is
______. (S-14, ½ Mark)
Q.2) The structural formula of vinyl chloride is __________. (W-14, ½ Mark)

14. Study of Vinyl Chloride (CH2=CH-Cl):
 Compound obtained by replacing one of the hydrogen
atom of an ethylene by halogen atom is called vinyl halide
(haloethylene).
 In vinyl chloride, chlorine atom is bonded to sp2
hybridized carbon atom of the C=C bond.
e.g. Vinyl chloride ( i.e. 1- chloroethene or chloroethylene)
CH2=CH-Cl
The group CH2=CH- is called vinyl group

15. Method of Preparation of Vinyl Chloride:
From Acetylene:
Q.1) How will you obtain Vinyl Chloride from Acetylene? (S-04 & W-07, 1 Mark)
Q.2) How will you bring about the following changes: (W-05, 1 Mark)
i) Vinyl Chloride from Acetylene?
Q.3) How will you prepare Vinyl Chloride from Acetylene?
(S-06, W-08, S-14, W-14, S-17, W-17 & W-19, 2 Mark)
Q.4) What happen when: Acetylene is treated with dil. HCl? (S-16 & W-18, 2 Mark)
Q.5) What happens when Acetylene gas passed through dil. HCl at 433 K in presence of
Hg2Cl2? (S-19, 2 Mark)
From acetylene:
When acetylene gas is passed through dilute hydrochloric acid at
about 433 K, in presence of Lewis acid like, Hg2Cl2 ; to form vinyl chloride.
HC CH + H Cl
Hg2Cl2
H2C CH Cl
Acetylene Vinyl chloride
433 K
in presence of Lewis acid
dil.
Vinyl chloride is colourless gas at room temperature, (Boiling point = 260 K.)

16. pramodpadole@gmail.com By Dr. Pramod R. Padole
Study of Allyl Chloride (CH2=CH-CH2-Cl):
Allyl chloride (3-Chloropropene) is the compound
obtained by replacing one of the hydrogens of the
methyl carbon in propene (propylene).
In allyl chloride, chlorine atom is bonded to sp3
hybridized carbon atom.

17. pramodpadole@gmail.com By Dr. Pramod R. Padole
Method of Preparation of Allyl Chloride:
From Propylene / Propene [ Inustrial Method]:
Q.1) How will you prepare Allyl Chloride from propylene (propene)?
(S-06, S-07, W-08, W-09,W-11, W-16, S-17, W-17 & W-19, 2 Mark)
Q.2) What happens when Propylene is treated with Cl2 at 500oC (773 K)? (W-14, 2 Mark)
Q.3) Complete the following reaction. (W-14, 2 Mark)
H2C CH CH2 H + Cl2
673-873 K
Gas phase
? + ?
From propene [Industrial Method]:
When propylene gas (propene) is heated with chlorine
at high temperature, 673 to 873 K (or 773 to 873 K);
to form allyl chloride, called as Industrial method.
H2C CH CH2 H + Cl Cl
Propylene
or Propene
673-873 K
Gas phase
Cl2
or
H2C CH CH2 Cl + H Cl
Allyl chloride
773-873 K
or
{Note: Liquid phase condition and low temperature favours addition across >C=C<
and gas phase condition at high temperature favours allylic chlorination.}

18. www.themegallery.com

19. Chemical Reaction of
Vinyl Chloride & Allyl Chloride:
Vinyl Chloride
Allyl Chloride

20. Action of aqueous KOH:
Q.1) How will you convert : Vinyl Chloride to Vinyl alcohol. (S-04, S-11 & W-13, 1 Mark)
Q.2) Complete the reaction :- ii) CH2 =CH-Cl + ? → CH2=CH-OH + ? (S-07 & S-14, 2 Mark)
Q.3) What happens when, Vinyl chloride is treated with aqueous KOH solution at high temperature
and high pressure? (S-13, W-17 & W-17, 2 Mark)
Action of aqueous KOH:
When vinyl chloride reacts with aqueous KOH at high temperature
and pressure; to form vinyl alcohol.
+
H2C CH Cl
Vinyl chloride
High temp.
High pressure + KCl
K OH
aq.
H2C CH OH
Vinyl alcohol
Q.1) How will you obtain Allyl alcohol from Allyl Chloride? (S-09 & S-10, 2 Mark)
Q.2) How will you bring the following transformations? (W-09, 2 Mark)
i) Allyl Chloride to Allyl alcohol
Q.3) What happen when: Allyl Chloride is treated or hearted with aq. KOH?
(S-16, W-18 & S-19, 2 Mark)
Action of aqueous KOH:
When allyl chloride is reacted with aq. KOH (aq.NaOH); to form allyl alcohol.
+ K OH
aq.
H2C CH CH2 Cl
Allyl chloride
+ K Cl
H2C CH CH2 OH
Allyl alcohol
Substitution

21. Reaction with alcoholic KOH (Potash):
Q.1) How will you convert Vinyl Chloride to Acetylene? (S-06 & W-11, 2 Mark)
Q.2) What is the action of alcoholic KOH ( Potash ) on Vinyl Chloride? (W-07 & W-10, 2 Mark)
Q.3) What happens when vinyl chloride is treated with alcoholic KOH?(S-14, S-15, W-17 & W-19, 2 Mark)
Action of alcoholic KOH: (Elimination reaction)
When vinyl chloride is reacted or treated or heated with alcoholic
solution of KOH, undergoes elimination reaction; to form acetylene.
Q.1) Complete the Reaction: CH2 =CH-CH2Cl + alc. KOH → ? + ? + ?
Q.2) What is the action of alcoholic KOH ( Potash ) on Allyl Chloride? (W-10, 2 Mark)
Q.3) What happen when: Allyl Chloride is hearted /treated/ reacted with alcoholic KOH?
(W-15 & W-17, 2 Mark)
Reaction with alcoholic KOH:
When allyl chloride is reacted / hearted /treated with alcoholic solution
of KOH, undergoes elimination reaction; to form allene (1,2-propadiene).
+
HC CH Cl
Vinyl chloride
Elimination Reaction
KCl + H2O
K
H OH
alcoholic
HC CH +
Acetylene
H2C C CH2 Cl
Allyl chloride
H2C C CH2
+
Elimination Reaction
KCl + H2O
K
OH
alcoholic
+
H Allene
1 2 3
(1,2-Propadiene)

22. pramodpadole@gmail.com
Comparison of Reactivity of :
Vinyl Chloride
(CH2=CH-Cl):
Reactivity
Allyl Chloride
(CH2=CH-CH2-Cl):
By Dr. Pramod R. Padole

23. pramodpadole@gmail.com By Dr. Pramod R. Padole
Comparison of Reactivity of Vinyl Chloride & Allyl Chloride:
Q.1) Explain why allyl chloride is more reactive than vinyl chloride.
(W-04, S-07, W-09 & W-13, 2-4 Mark)
Q.2) Compare the reactivity of allyl chloride with vinyl chloride.
(S-05, S-11, S-12 S-14 & W-14, 4 Mark)
Q.3) Explain the reactivity of allyl chloride. (S-09 & S-10, 2 Mark)
Q.4) Explain the reactivity of vinyl chloride. (S-10, 2 Mark)
Q.5) In allyl chloride, the chlorine atom is attached to ___ hyridised carbon atom.
(W-11, ½ Mark)
Q.6) Compare the reactivity of vinyl chloride and allyl chloride. (S-15, 4 Mark)
Q.7) Explain why chlorine in vinyl chloride is less reactive towards nucleophilic substitution
than that in allyl chloride. (S-16, 4 Mark)
Q.8) Chlorine in Vinyl chloride is less reactive towards nucleophilic substitution than that in
allyl chloride. Explain why? (W-16, 4 Mark)
Q.9) Compare the reactivity of vinyl chloride and allyl chloride towards nucleophilic
substitution reaction. (S-18, 4 Mark)

24. pramodpadole@gmail.com By Dr. Pramod R. Padole
Comparison of Reactivity of Vinyl Chloride & Allyl Chloride:
Comparison of reactivity of Vinyl chloride & Allyl chloride:
The reason for the more reactivity of allyl chloride than vinyl chloride is due to the
following facts:
i) Percentage of ‘s’ character in C-Cl bond:
In vinyl chloride, chlorine atom is attached to sp2 hybridised carbon atom,
whereas in allyl chloride, chlorine atom is attached to sp3 hybridised carbon
atom.
Hence C-Cl bond in vinyl chloride has greater “%S” character than in allyl chloride.
So C-Cl bond in vinyl chloride is short (1.69 A0) than in allyl chloride (1.77 A0)

25. pramodpadole@gmail.com By Dr. Pramod R. Padole
Comparison of Reactivity of Vinyl Chloride & Allyl Chloride:
ii) Extra stability of allyl carbocation:
When allyl chloride loses chloride ion, allyl carbonium ion is formed.
Later get stabilized by resonance.
Delocalisation of +ve charge:
But,
H2C CH CH2 Cl
Allyl chloride
H2C CH CH2 + Cl
Allyl carbonium ion
H2C CH CH2 CH2 CH CH2
 CH2 C CH2
Resonance structures of allyl carbocation Resonance hybrid
CH2=CH Cl X No Resonating structure of
Vinyl chloride

26. pramodpadole@gmail.com By Dr. Pramod R. Padole
Comparison of Reactivity of Vinyl Chloride & Allyl Chloride:
iii) Double bond character in C-Cl bond:
'p' orbital on chlorine in vinyl chloride interacts with the 'p'
orbital of C=C bond on adjacent carbon atoms. As a result of
this delocalization, the C-Cl bond acquires partial double
bond character .

27. pramodpadole@gmail.com By Dr. Pramod R. Padole
Comparison of Reactivity of Vinyl Chloride & Allyl Chloride:
iii) Double bond character in C-Cl bond:
While in allyl chloride, this type of interaction is not possible
because the p orbital of chlorine atom is separated from the
p - MO of the double bond by a saturated sp3 hybridised
carbon atom.
Thus, Cl-atom in vinyl chloride is strongly bonded to C-atom
and hence cannot be replaced easily by nucleophile as
compared to allyl chloride.

28. LOGO

29. LOGO
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Alkenyl Halides by Dr Pramod R. Padole
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