Page 46 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

VI- Potassium Bromate, KBrO3
Properties
Strong primary standard oxidant

Applications

Potassium bromate solution is used as a source of bromine

Reaction of BrO3–/ Br– in acid solution
On acidification, BrO3–/ Br– mixture is quantitatively converted to

Br2

BrO3− + 5Br− + 6H+ 3Br2 + 3H2O

Reduction Half reaction of Br2

3Br2 + 6e 6Br−

BrO3− ≡ 3Br2 ≡ 6Br− ≡ 6e

Note Standard Br2 solutions cannot be used as such due to volatility of
Br2

Determination of Phenol (back titration)

Substitution Reaction (Redox reaction)----Bromination of phenol

OH OH
Br Br
+ 3 Br2
+ 3HBr

C6H6O + 3Br2 → Br
-2, +6, 6C = - 4
C6H3OBr3 + 3HBr
-2, -3, +3, 6C = +2

Phenol ------------loss of 6e
3Br2 → 6Br− ------------- gain of 6e
C6H6O ≡ 3Br2 ≡ 6Br− ≡ 6e

Eq.wt phenol = Mw / 6

- xss unreacted Br2 is titrated iodometrically

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