• When two different halogens react with each other, interhalogen
compounds are formed.
• In general, XYn where n=1 , 3 , 5 , 7
X is halogen atom which is less electronegative and larger in size.
Y is halogen atom which is more electronegative than X and smaller in
• The interhalogen compounds can be grouped into four categories :
1) XY : ClF , BrF , BrCl , ICl , IBr
2) XY3: ClF3 , BrF3 , IF3 , ICl3
3) XY5 : ClF5 , BrF5 , IF5
4) XY7 : IF7
PREPARATION OF INTERHALOGEN
i) Halogen molecules react directly to form interhalogen compounds.
Ex: Equal volume of chlorine and fluorine combine at 473K to form
ii)A halogen molecule reacts with lower interhalogen to form a new
Ex: Fluorine reacts with iodine pentafluoride at 543K to form iodine
SOME PROPERTIES OF INTERHALOGEN
• PHYSICAL STATE : These molecules are covalent in nature.
• COLOUR : These compounds are colourless.
• BOILING POINT : Boiling point increases with increase with
• THERMAL STABILITY: Thermal stability decreases with decrease in
• REACTIVITY : AB type of compounds are more reactive than A2 and B2
INTERHALOGEN COMPOUNDS OF XY TYPE
Eg : Iodine monobromide (IBr)
PREPARATION : It is obtained by the direct combination of elements.
It is hard, crystalline solid of grey violet colour.
Its vapour dissociate to a small extent on heating.
IBr is an electrical conductor when in molten state.
INTERHALOGEN COMPOUNDS OF XY3 TYPE
Eg : Chlorine trifluoride (ClF3)
PREPARATION : It is prepared by the action of Cl2 on F2 at 200-300◦C in a Cu vessel.
It is a colourless gas which condenses to give a pale green liquid.
Hydrolysis: It is hydrolysed by H20 forming ClOF.
Action of F2 and Br2:
i)When ClF3 reacts with F2 , it gets fluorinated with F2 , forming the higher
ii) When ClF3 reacts with Br2 at 10 ◦C, BrF3 is obtained. Bent T Shape
INTERHALOGEN COMPOUNDS OF XY5 TYPE
Eg : Iodine pentafluoride (IF5)
PREPARATION: It is prepared by the direct combination of I2
and F2 (excess).
It is a colourless liquid whose melting point is 9.6 ◦C.
Good conductor of electricity.
Hydrolysis: It is hydrolysed by water to give halogen acid and oxy-acid of
larger halogen atom.
INTERHALOGEN COMPOUNDS OF XY7 TYPE
Eg : Iodine heptafluoride (IF7)
PREPARATION: It is prepared by the action of F2 on IF5 at 250◦C -300◦C.
It is gas at ordinary temperature.
Hydrolysis: It is hydrolysed by water giving HF and H5IO6.
PROPERTIES OF PSEUDOHALOGENS
These are volatile.
Pseudohalogens, like the halogens, add at ethylenic double bond
Pseudohalogens , like the halogens, react with alkalies.
Pseudohalogens form covalent pseudohalides.
• Eg : Thiocyanogen (SCN)2
PREPARATION: It is prepared by Pb(SCN)2 with Br2
at 0 ◦C.
in the real solution
It is yellow solid
Insoluble in water.
It oxidises Cu(I) salts to Cu(II) salts.
Sulphur is precipitated from H2S.