preparation and properties of interhalogen compounds

1. BrF3(Bromine trifluoride)
Preparation
Br2(vapour) + 2F2 N 2BrF3
 ClF3 + Br2 10oC BrF3 + BrCl
 3F2 + 2HBr → 2BrF3 + H2
 3BrF → BrF3 + Br2
Properties
It is a colourless fuming liquid with b.pt=127.6o and is exceedingly reactive
It is violently decomposed by H2O and organic materials
It reacts with glass and silica materials and sets fire to wood, paper etc. it
displaces O2 from oxides like SiO2,CuO etc
3SiO2 + 4BrF3 → 3SiF4 +2Br2 +3O2
BrF3 +Br2 → 3BrF
It has high electrical conductivity and ionizes as
2BrF3→ BrF2+ + BrF4-
←

2. Action on metal fluorides
KF+ BrF3→ K+[BrF4]3-
Action on metals, metal oxides and chlorides
6M +2BrF3→6MF+ Br2
3MCl + BrF3→ 3MF+ BrCl2
ICl3 (Iodine trichloride)
Preparation
3Cl2(excess) +I2 → 2ICl3
Cl2(excess) + Icl → ICl3
I2O5 (heated) + 10 HCl (dry gas) → 2ICl3 + 5H2O + 2Cl2
4HI + 4Cl2 → 4HCl +I2 +ICl +ICl3
Properties
It is a lemon-yellow crystalline solid which fumes readily. It is soluble in organic solvents.
Liq.NH3 and liq.SO2
MCl+ICl3 ICl3.MI (addition compound) expose to air ICl3 + MC

3. 2ICl3 +3H2O → 5HCl + HIO3 + Icl
ICl3 → Icl + Cl2
4ICl3 + 3CS2→CCl4 + 2CsCl2 + 2S2Cl2+ 2I2
3 ICl3 +12KOH → 9KCl + KI + 2KIO3 +6H2O
4ICl3→ [ICl2]+ + [ICl4]- (ionisation)
←
2[ICl2]+ + 2e- → I2 +2Cl2 (at cathode)
2[ICl4]- -2e- → I2 + 4Cl2 (at anode)
ClF5 (chlorine pentafluoride)
Preparation:
ClF3+ F2(excess) 350oC ClF5
Heated at 200oC
KCl + 3F2 → ClF5 + KF
Properties:
It is a colorless gas with a sweet odor.
ClF5 → ClF3 + F2
←
ClF5 +2H2O → ClO2F(chloryl fluoride) + 4HF

4. BrF5( Bromine pentafluoride)
Preparation
5F2 (excess)+ Br2 → 2BrF5
F2+BrF3 → BrF5
Properties
It is a colourless liquid
Metals and non metals catch fire when dropped into it
BrF5+ H2O → 2HF + BrOF3(oxy fluoride)
2 BrF5 → Br2 + 5F2
IF5(iodine pentafluoride)
Preparation
I2(excess) + 5F2 → 2IF5
2I2O5 (heated)+ 10F2 → 4IF5 + 5O2
5AgF + 3I2 red heat→ IF5 + 5AgI
10AgF + I2 → 2IF5 + 10Ag

5. Propeirtes:
It is a colourless liquid. It vapours attack respiratory organs. It is a very poor conductor
7IF5 →I2 + 5IF7
2IF5 +5H2O → I2O5 +10HF
3IF5 + I2O5 → 5IOF3
3IOF3 →100oC IF5(black) + IO2F(white solid)
It is a good conductor of electricity and ionizes as
2IF5 → IF4+ + IF6-
←
IF7(iodine heptafluoride) : preparation
7F2(excess)+ I2 300oC 2IF7
IF5+ F2 270oC IF7
Properties
It is a colourless gas having mustly odour. It can be condensed to a colourless liquid. It
react with metals, non metals , water to give periodate and fluoride ions. It explodes
when heated with H2. it is slowly decomposed by water. Two of fluorine atoms present
in IF7 can easily be removed

6. ClF (Chlorine monofluoride)
Preparation:
 It is formed by the action of Cl2 on HF at the temperature of liquid air
Cl2+ HF→ ClF+ HCl
 it is also formed when F2 and Cl2 are heated together in a copper vessel at 50oC
F2+Cl2→ 2ClF
Properties
It is colorless gas
It dissociates when heated strongly
2ClF → Cl2+F2
It reacts with a number of metals, even more vigorously than F2. it inflames cotton-wool
and filter paper in the same way as F2

7. ICl (iodine monochloride)
Preparations:
It is obtained as a dark red liquid by passingCl2 over I2 or by heating I2 with KClO3
I2+ Cl2→ 2ICl
KClO3 + I2 → KIO3 +ICl
Properties:
i) It solidifies on standing even at room temperature(15-25oc). from this solid two forms
of the compound may be obtained.
 These are a) α-form which is ruby-red. It is a stable form(m.pt-27.2o)
 b) β-form which is red rhombic. It is a meta stable form(m/pt-14o, b.pt-97.4o)
 These two forms are identical in the gaseous state.These can be separated by cooling the
liquid below 14o and by adding to the a crystal of either of the two forms.
ii) ICl is soluble in water and gets hydrolysed by it
5ICl +3H2O → 2I2+ HIO3 +5HCl

8. iii) It dissolves in alkalies to form I2, iodate and chloride
5ICl + 6NaOH → 2I2 + NaIO2 + 5NaCl + 3H2O
iv) It is an electrical conductor when in the molten state. Thus when ICl is in the molten state,
it ionizes as
2ICl ←
→ I+ + ICl2- (ionization)
2I+ + 2e- → I2 (at cathode)
2ICl2
- → I2 +2Cl2 +2e- (at anode)
The liberation of I2 at cathode and both I2 and Cl2 at anode shows that ICl is an ionic compound and in
it iodine is present as I+ ion (unipositive iodine)
v) ICl forms charge-transfer complexes with organic bases like pyridine and dioxane
Uses:
 it is used to iodate and chlorinate organic compounds
 the solution of ICl is used as a catalyst in oxidizingAs2O3 by Ce(SO4)2
 It is also used to prepare polyhalides
 a solution of Icl in glacial acetic acid is used for the determination of iodine number
which measures the unsaturation of oils and fats

9. ClF3(chlorine trifluoride)
Preparations:Cl2 is heated with excess of F2 in copper vessel at 250oC
Cl2 + 3F2 → 2ClF3
Properties
It is a colorless gas which condense to give a pale-green liquid(b.pt=-12oc).
It is exceedingly reactive and attacks a number of metals.
It also attacks glass vigorously.
It reacts with water to give a red liquid which crystallize at -70oC. The compound
formed is ClFO.
ClF3+ H2O → ClFO + 2HF
Uses:
 it has been used as a fluorinating agent, as an incendiary and in cutting oil well
tubes
 It is used as an oxidizer for propellants