Interhalogen compounds

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) 350 o C ClF5 Heated at 200 o C 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 2I 2 O 5 (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 Cl 2 on HF at the temperature of liquid air Cl 2 + HF → ClF + HCl it is also formed when F 2 and Cl 2 are heated together in a copper vessel at 50 o C F 2 +Cl 2 → 2ClF Properties It is colorless gas It dissociates when heated strongly 2ClF → Cl 2 +F 2 It reacts with a number of metals, even more vigorously than F 2 . it inflames cotton-wool and filter paper in the same way as F 2

7. ICl (iodine monochloride ) Preparations: It is obtained as a dark red liquid by passing Cl2 over I2 or by heating I2 with KClO3 I2+ Cl2 → 2ICl KClO3 + I2 → KIO 3 + ICl Properties: 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 5 ICl +3H2O → 2I 2 + HIO 3 +5HCl

8. iii) It dissolves in alkalies to form I2, iodate and chloride 5ICl + 6NaOH → 2I2 + NaIO 2 + 5NaCl + 3H 2 O 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- → I 2 (at cathode) 2ICl 2 - → I 2 +2Cl 2 +2e- (at anode) The liberation of I 2 at cathode and both I 2 and Cl 2 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 oxidizing As2O3 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: Cl 2 is heated with excess of F 2 in copper vessel at 250 o C Cl 2 + 3F 2 → 2ClF 3 Properties It is a colorless gas which condense to give a pale-green liquid(b.pt=-12 o c). 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 -70 o C. The compound formed is ClFO . ClF 3 + H 2 O → 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