It includes three parts. The first part consists of hydroxylation of alkenes and alkynes with KMnO4, OsO4, and Per acids with examples. The second part consists of hypo-halous-acid addition in alkenes and cyclo alkenes with examples. The third part consists of hydroboration oxidation in alkenes and alkynes by Anti-Markovnikov rule and CSIR questions.

1. Presented by:
K. Muthu Kannan

2. I . Hydroxylation
(i) Reaction with Potassium permanganate
(ii) Reaction with Osmium tetroxide
(iii) Reaction via epoxides
II . Hypohalous acid addition
(i) Addition with alkenes
(ii) Addition with cyclo-alkenes
(iii) Addition with alkynes
III . Hydroboration-Oxidation
(i) Hydroboration
(ii) Oxidation

4. Dilute alkaline potassium permanganate at low temperature, leads to
the formation of vicinal diols (glycols).
C C + H2O
dil. alk.KMnO4
273K
C C
OH OH
a vic-diol (glycol)
For examble,
+ H2O
dil. alk.KMnO4
273K
C
OH
Alkene
Ethene
1,2-Ethane diol
C
OH
C C
H
H
H
H
H
H
H
H

5. It involves the intermediate formation of a cyclic manganese ester through
electrophilic addition, as shown below:
C
H
C
H
R''
R'
Mn
O O
O O
H
C
H
C R''
R'
Mn
O O
O O
OH
H
C
H
C R''
R'
OH OH
a vic-diol
(Cis- Hydroxylation)
R'
H
C
H
C R''
O O
Mn
O O
OH
R'
H
C
H
C R''
O O
Mn
O O
OH
R'
H
C
H
C R
''
HO O
Mn
O OH
O
H
R'
H
C
H
C R''
HO O
H

6. It follows the above mechanism that where structure permits, the resulting
1,2-diol is a cis diol. If an unsymmetrical alkane is used, the syn dihydroxylation
produces a pair of enantiomers.
K M n o 4
O H , C o ld
O H
O H
O H
O H
+
B o th a re e n a n tio m e rs
3 -M e th y lh e x -2 -e n e
KMnO4 , OH
Cold
OH
OH
H
H3C
+
OH
OH
H
H3C
Propene
1,2-propanediol. Both are enantiomers

7. C
H3C
H3C
CHCH2CH3 + 3 [O]
KMnO4 / OH
C
H3C
H3C
O + CH3CH2COOH
Acetone
Propionic acid
2-Methyl-2-pentene
High
Temperature
In the presence of acidic or alkaline permanganate at higher temperature,
alkenes undergo oxidative cleavage or degradation through the intermediate glycols to
form aldehydes, ketones and acids, depending upon the condition of the experiment,
nature of the alkene and the oxidising agent used.
+ dil.KMnO4
278K
O
O
H
H
Mn
O
H2O
H
H
OH
OH
Cis-1,2-cyclohexanediol
O

8. This leads to the hydroxylation of the double bond of the alkene at
room temperature.
C C C C
OH OH
a vic-diol (glycol)
For examble,
CH3CH CH2
Room temperature
CH2
OH
Alkene
Propene
1,2-Propane diol
H3CH2C
OH
OsO4
Room temperature
OsO4

9. This reaction proceeds through the formation of intermediate cyclic
osmate ester, to form cis-hydroxylation product.
C
H
C
H
R
R
Os
O O
O O
H
C
H
C R
R
Os
O O
O O
H
C
H
C R
R
OH OH
a vic-diol
(Cis- Hydroxylation)
NaHSO4
H2O + Os
O O
OH
HO
Osmium tetroxide is highly toxic. Between potassium permanganate and
osmium tetroxide as hydroxylating reagent potassium permanganate is cheaper and
safer but gives poor yield of diol. In contrast osmium tetroxide is expansive and toxic
but gives better yields. Because of the cyclic nature of the intermediate osmate ester,
cycloalkane also give cis-1,2-diols.

10. Os
O O
OH
HO
+
O
N
O
H3C
NMO
N-methylmorpholine N-oxide
Os
O O
O
O
O
N
NMO
+
CH3
Potassium ferricyanide K3[Fe(CN)6] or NMO (N-methylmorpholine-
N-oxide) is added to the reaction and it deoxidizes the Os+6 species back into
OsO4 which can perform another oxidation of the alkene.
The below reaction shows conclusively that action of osmium tetroxide or
potassium permanganate on alkenes leads to cis-hydroxylation of the double bond.
i.e., they are syn stereoselective oxidations.

11. C
C
H
CH3
CH3
H
OsO4 or
KMnO4
H
CH3
OH
H
CH3
OH
H
CH3
H
HO
CH3
H OH
CH3
H OH
CH3
HO H
CH3
HO H
Cis-2-butene
Meso-2,3-butanediol
OH
CH3

12. C
C
H
CH3
H
H3C
OsO4 or
KMnO4
H
CH3
OH
H3C
H
OH
H
OH
CH3
H
H3C
HO
CH3
H OH
CH3
HO H
CH3
HO H
CH3
H OH
Trans-2-butene
Both are Enantiomers 2,3-butanediol

13. Reaction of alkenes with per acids, like per-benzoic acid, per-oxy-
trifluoroacetic acid, m-CPBA etc. followed by boiling with water leads to the
hydroxylation of double bond to give trans-diols.
C
C
-(RCOOH)
C
C
O
C
C
HO
OH
H3O
Alkene 1,2-diol
RCOOOH
epoxide
E
x
:
H
2
C C
H
C
H
3
R
C
O
O
O
H
-R
C
O
O
H
H
2
C C
H
C
H
3
O
H
3O
H
2
C
H
C C
H
3
O
H
O
H
P
ropene
1,2-transdiol

14. C
C
+
O
H
O C
O
R -(RCOOH)
C
C
O
C
C
H3O
Alkene Peracid
O
H
-H2O
H2O
C
C
OH
H2O
H2O
C
C
OH
HO
1,2-Diol
This sequence of reaction ,unlike the earlier reactions with potassium
permanganate or osmium tetroxide, this leads to trans-1,2-diols, as illustrated below,

15. Me
KMnO4
OH , cold
OH
OH
Me
+
Me OH
OH
1)
2)
Me
KMnO4 , H2O , Cold
OsO4 , NaHSO3 , H2O
Me OH
OH
or
Me OH
OH
+
MeO
OMe
OTIPS
AD
(DHQ)2PHAL
MeO
OMe
OTIPS
OH
OH
3)

16. 1. m-CPBA , OC(CH3)2
2. H2O , H
OH
OH
H3C H
H
H
2S-1,2-propanediol
OH
OH
H H
H3C
H
2R-1,2-propanediol
+
4)
m -C PB A , H 2O
O H
O H
H
H
+
H
H
O H
O H
(2R ,3R )-2,3-hexanediol (2S,3S)-2,3-hexanediol
C is-2-hexene
5)
OsO4
H2S
HO OH
H H
Meso-3,4-hexanediol
3-hexene
6)
HO OH
H H
+

17. OEt
O
(DHQD)2PHAL
AD
OEt
O
OH
OH
(DHQD)2PHAL
AD
OH
OH
O
O
OMe
(DHQD)2PYDZ
AD
O
O
OMe
OH
OH
7)
8)
9)

19. Aqueous solution of halogens add to alkenes to form halohydrins, i.e.,
compounds containing both halogen and hydroxyl groups on adjacent carbons.
H2C
OH
CH2
2- Chloroethanol
C C
H
H
H H
+ Cl OH
Cl
The addition of hypohalous acid to an asymmetric alkene follows
Markovnikov’s rule.
For example,
H3CHC
OH
CH2Cl
H3CHC CH2 + Cl OH
1-Chloro-2-propanol

20. In this reaction, a halonium ion formed by the cleavage of HO-X bond, acts as
an electrophile. It adds to the alkene to form a cyclic halonium ion which is attacked by
hydroxide ion or water in a trans manner as shown below.
Step 1
R C
H
CH2
Cl OH
R
H
C CH2
Cl
+ OH
Cyclic chloronium ion
Step 2
R
H
C CH2
Cl
R C
H
CH2
Cl
OH
Opening of the cyclic chloronium ion in step(2) is favoured in that direction which
can give the more stable carbocation. As expected, the reactions give trans product.

21. C CH2 + C6H5SCl
H3CH2C
H3C
C CH2
CH3
H3CH2C
Cl
SC6H5
2-Methylpropene Trans-product
For example,
C C
H3C
H3C
H
H
Hg(OAc)2
H2O , THF
C
H2
C
CH3
CH3
HO HgOAc
2-Methylpropene Trans product
H
H
H
H
H
C
l
B
r
C
l
B
r
H
g
C
l
B
r
I
O
H
2
C
l
B
r
O
H
O
H
(
O
A
c
)
2
R
S C
l
R
2
B H
O
S
O
3
H
E
l
e
c
t
r
o
p
h
i
l
e
sN
u
c
l
o
p
h
i
l
e
s
H O B r
B r
O H
2-B utene
3-B rom o-2-hydroxybutane

22. In aqueous solution of chlorine and bromine, the hydroxyl group and halogen
group add opposite faces to double faces to double bond.
For example,
+ Br2 + H2O
OH
H
H
Br
Trans-2-Bromocyclohexanol
It involves attack of hypo-halo-acids to form bridge head halonium ion with
cycloalkanes followed by attack of hydroxide ion from the backside to form trans product.
+ B
r O
H
B
r
+ O
H
C
y
c
lo
h
e
x
e
n
e C
y
c
licb
ro
m
o
n
iu
mio
n
ste
p1

23. Br
OH OH
H
Br
H
Cyclic bromonium ion
Trans-2-Bromocyclohexanol
step 2
+ Cl2 + H2O
OH
Cl
Trans -2-chlorocyclopentanol
Cyclo pentene
OH
Cl
H
H
Cyclo pentene
Trans -2-chlorocyclopentanol
For example,
N O
O
Cl
(NCS)
OH , DMF

24. H2O , DMSO
(NBS)
N O
O
Br
OH
Br
HOCl
Cl Cl
OH
OH
+
1-Methylcyclohexene 1S,2S-2-chlorocyclohexanol 1R,2R-2-chlorocyclohexanol
SOCl2
Cl
OH
OH

25. This addition proceeds in two steps to form di halo-carbonyl compounds,
as shown below;
OH
Cl
C C R'
R C C R'
R C C R'
R
HOCl
HOCl
O
Cl
Cl
Alkyne
Hypohalide
compound
Dichlorocarbonyl
compound
Alkyne is react with hypochlorous acid to give chloronium ion, then
hydroxide ion react chlorinated carbon in back side approach to form a stable compound
like hydro-chlorinated alkene. Further is reacted with hypochlorous acid, it will form a
dichloro-dihydroxy alkane. Which is readily converted into carbonyl group.

26. R C C R'
Cl OH
R C C R'
OH
R C C R'
OH
Cl
Cl OH
R C C R'
OH
Cl
Cl
O
H
-H2O
R C C R'
Cl
Cl
O
Cl
Alkyne
Hydroxy chlorinated
alkene
Dichloro-carbonyl alkane
compound
Mechanism:

27. 1)
B r2 / H 2 O B r
O H
Si(CH3)3Cl
CH2Br
OH
3)
OH
H2C
CH3
CH3
HOBr
H2C
CH3
CH3
OH
Br
2)

28. C C
H3C H
HO-Cl
C C
H3C H C C
H3C H
OH Cl
O Cl
Cl
HO-Cl
Propyne
1,1-Dichloropropanone
2-Chloropropanol
4)
HO-Br
HO
Br
5)
HO
HO-Cl
HO
3-Methyl-2-pentanol
3_Methylpentan-2-one
6)
Cl
HO

30. The hydroboration-oxidation is a two step hydration reaction that converts
an alkene into an alcohol. The process result in the syn addition of a hydrogen and a
hydroxyl group.
Hydroboration-oxidation is an anti-Markovnikov reaction, with the
hydroxyl group attaching to the less substituted carbon.
H 2 C C H 2
B H 3 / T H F
H 2 C C H 2
B H 2
H 2 O 2
N a O H
H 3 C C H 2
O H
H
+ B H 2 O H
The following types of boranes used in hydroboration,
B
H H
H
Borane (BH3)
B
H
B
H
H
H
H
H
Diborane (B2H6)
9-BBN (9-Borabicyclo[3.3.1]nonane)
B
H
H
B

31. B
H
Dimesitylborane (C6H2Me3)2BH
B
H
Disiamylborane (C5H11)2BH
B S
H
H
CH3
H
CH3
Borane dimethylsulfide - BH3S(CH3)2
B
H
B
H H
C
H C
CH
Me
Me
Me
Me
CH
Me
Me
Me
Me
Thexylborane - [Me2CHCMe2BH2]2
O
O
B H
Pinacolborane - (CH3)4C2O2BH
O
O
B
H
Catecholborane - (C6H4O2BH)

32. Borane, forms a stable complex wit cyclic ether like tetrahydrofuran(THF), is
commercially available as a solution of borane in THF, and is used as such in this reaction
called hydroboration addition of H and B to an alkene.
For example,
B
H
3
H
2
C C
H
2 C
H
3
C
H
2
B
H
2
H
2
C C
H
2
H
2
C C
H
2
(C
H
3
C
H
2
)2
B
H (C
H
3
C
H
2
)3
B
T
rie
th
y
lb
o
ra
n
e
S
im
ila
rly
,
3
C
H
3
C
H C
H
2 + B
H
3 (C
H
3
C
H
2
C
H
2
)3
B
P
ro
p
e
n
e T
ri-n
-p
ro
p
y
lb
o
ra
n
e
3
H
2
C C
H
2 + B
H
3 (
C
H
3
C
H
2
)
3
B
E
t
h
e
n
e T
r
i
e
t
h
y
l
b
o
r
a
n
e

33. Hydroboration does not involve a free carbocation intermediate. Actually, there
is a simultaneous addition of hydrogen ad boron to alkene via pi-complex to form a four
centred transition state in which boron is attached to the least hindered i.e., leas substituted
carbon of the double bond. Where structure permits, it show stereoselective.
H3C C
H
CH2
H BH2
H3C C
H
CH2
BH2
H
CH3CH2CH2 B H
H
CH3CH CH2
CH3CH2CH2 B H
CH2CH2CH3
CH3CH CH2
(CH3CH2CH2)3B
Di-n-propylborane
Tri-n-propylbornane
Transition state
n-propylborane

34. As the transition state approached, the carbon which is losing the pi-electrons
becomes increasingly electron deficient, and tends to take up the nearby hydrogen,
together with its electron pair held to boron.
Boron with sextet of electrons, is itself electron deficient but as it gains the
pi-electrons, it is increasingly willing to release hydrogen along with its electron pair.
This four centred mechanism is supported by the fact that hydroboration is a
cis addition. Whereas, hydrogen adds without electrons in ordinary electrophilic
addition, it adds here with electrons in hydroboration.
It is, therefore, natural to expect that addition in hydroboration should be
anti-Markovnikov, and this is actually so, it may be noted tht the rate of addition of
borane to alkenes decreases with the increase in the alkyl substituents on the double
bond, as expected from its four centred transition state mechanism.

35. The oxidation of tri-alkylboranes proceeds in the following steps;
(
C
H
3
C
H
2
C
H
2
)
3
B+ 3
H
2
O
2 +3
N
a
O
H 3
C
H
3
C
H
2
C
H
2
O
H+ N
a
3
B
O
3 +3
H
2
O
T
r
i
-
n
-
p
r
o
p
y
l
b
o
r
a
n
e 1
-
P
r
o
p
a
n
o
l S
o
d
i
u
m
b
o
r
a
t
e
S
te
p1
O
H H
+ O
O
H H
2
O + O
O
H
Trialkyl boranes are generally not isolated. They are directly oxidised to
alcohols to alcohols by hydrogen peroxide in aqueous sodium hydroxide.

36. Step 3
B
H3CH2CH2C
H3CH2CH2C
O
H3CH2CH2C
OH B
H3CH2CH2C
Mono-n-propoxy-di-n-propylborane
CH2CH2CH3
OH
H3CH2CH2C
O
H3CH2CH2C
B
H3CH2CH2C
OH
CH3CH2CH2OH
+
1-propanol
Step 2
(CH3CH2CH2)3B + OOH (CH3CH2CH2)3B O OH
B
H3CH2CH2C
H3CH2CH2C
O
HO
OH B
H3CH2CH2C
CH2CH2CH3
OH
HO
O
B
CH3CH2CH2OH
+
1-propanol
OH
OH
H3CH2CH2C
OOH
B OH
H3CH2CH2C
H3CH2CH2C

37. B
HO
H3CH2CH2C
O
HO
OH B
HO
CH2CH2CH3
OH
HO
O
B
CH3CH2CH2OH
+
1-propanol
OH
OH
HO
OOH
B OH
HO
H3CH2CH2C
Similarly, mono-n-prop-oxy-di-n-propyl-borane can react with excess
alkaline hydrogen peroxide to form successively di-n-prop-oxy-mono-n-propyl-
borane and tri-n-prop-oxy-borane. The tri-n-prop-oxy-borane then hydrolysed to n-
propyl alcohol.
It may be noted that the net result of this hydroboration-oxidation of
alkenes is the anti-morkovnikov addition of water to alkenes. The hydroboration has
immense utility as trialkyl-boranes undergo a variety of useful transformations to
yield anti-morkovnikov products.

38. Cyclo-alkylborane on oxidation with alkaline hydrogen peroxide gives
cycloalkanol. The net result of this reaction is addition of water in which H and OH are
added to the same face of the double bond i.e., syn addition. For example,
H
H3C
1) B2H6 ; Diglyme
2) H2O2 ; OH
H
H3C
H OH
1-Methylcyclopentene
Trans-2-Methylcyclopentanol
2 H2C C
CH3
CH3
BH3 / H2O2
NaOH
C
H
CH3
CH3 + BH(OH)2
2 H2C
OH
H
H3C
H2O
H2SO4 H3C
H
H
OH
For example,

39. 1) The major product formed in the hydroboration-oxidation of 1-methylcyclopentene
is
GATE
2001
A) B)
C)
D)
CH3 CH3
CH3
CH3
OH
OH
OH
O

40. Solution
BH3/THF
H
H2
B BH2
H
OOH
H2B O OH
O
H2B OH
O
H2B
OH
OH O
H
-BH2OH
H O O H + OH H O O + H2O

41. 2) Hydroboration of 1-methylcyclopentene using B2D6, followed by treatement withalkaline
hydrogen peroxide gives
GATE
2003
A) B) C) D)
H OH H OH
D
OH
D
OH
H
OH
OH
H
Solution
B2D6
H
D
BD2
H
D
OH
H2O2, NaOH

42. 3) The major product formed in the hydroboration reaction is :
GATE
2020
O
H
H
BH3/THF
H2O2 , NaOH
O
H
H
O
H
H
O
H
H
O
H
H
a) b) c) d)
HO
HO
HO
HO

43. O
H
H
Solution
O
H
H
H
H2B
O
H
H
H2B
H
H2O2
NaOH
O
H
H
H
HO
Major product
Minor product
H2O2
NaOH
O
H
H
HO
H
Major product
Minor product
BH3/THF
BH3/THF
O
H
H
H
H2B
O
H
H
H2B
H

44. 4) The major product form in the reaction between 1,5-cyclooctadiene with diborane
(0.5equivalent) is ?
GATE
2002
a)
BH2
b)
B
H
c) d)
BH2
H2B
B
H

45. Solution
H BH2 H
BH2
B
B
H
H
Less stable
More stable
H
B
H
B H
B

46. Reference:
Modern Organic Chemistry
By M.K.Jain and S.C.Sharma