(A) Compounds of the AX type :
Iodine monochloride, ICI
(i) It is prepared by adding iodine to liquid chlorine and the mixture is kept at 35∘C for 24 hours to ensure a complete reaction.
It is obtained as a dark liquid that solidifies on long-standing at room temperature.
(ii) It is also prepared by heating iodine with potassium chlorate.
(iii) It is also formed in an aqueous solution when hydrochloric acid reacts with a mixture of potassium iodide and potassium iodate.
6HCl+KIO3+5KI⟶ KKCl + 3H2O + 3l2
KIO3+2l2+6HCl⟶KCl+5Cl + 3H2O
The reaction is quantitative and the two stages can be observed by the appearance and disappearance of the red colour of the free iodine.
(i) It is a dimorphic solid. Its stable form is b-form which is ruby red needle-like crystals, m.p. 27.2∘C and the metastable form is b-form which is a red rhombic solid, m.p.14∘C and b.p. 97.4∘C. These two forms are identical in a gaseous state. These can be separated by cooling the liquid 1Cl below 14∘C and by adding to the liquid a crystal of either of the two forms.
(ii) Some metal chlorides like those of potassium, rubidium, caesium, and ammonium dissolve in the liquid iodine monochloride to form polyhalides.
while LiCl1NaCl and BaCl2 are insoluble in liquid ICl.
(iii) It is readily hydrolyzed by water (in a neutral solution).
(iv) It reacts with alkali to liberate Iodine.
(v) On electrolysis, Iodine is set free at the cathode and chlorine at the anode thereby indicating that the compound is a chloride of monovalent iodine (1+).
2Cl⟶1+ + ICl2−
At Cathode :21+ + 2e− ⟶ I2
At Anode : 2Cl2− − 2e− ⟶ I2+2Cl2
Therefore lig. ∣Cl is used as an ionizing solvent in which the heavier alkali-metal chlorides (KCl, RbCl, CsCl) dissolve.
(vi) It reacts with AlCl3 and AgClO4 in nitrobenzene.
AlCl3 + ICl ⟶ H+ + (AlCl4)−
At Anode : AgClO4+ICl⟶AgCl+IClO4
(vii) In strong hydrochloric acid it forms HICl2.
H+ + Cl+ + Cl ⟶ H+ + HCl2−
(viii) It reacts with many metals such as Mg, Ca, Ni, Cu, Zn, Fe, Co, etc. to form chlorides.
(ix) It converts acetanilide into 4−iodo ocetahylides and salicylic acid into 3,5 di-iodosalicylic acid.
(x) ICl forms charge transfer-type complexes with organic bases like pyridine and dioxane.
Chlorine monofluoride, CIF
(i) By the direct combination of Cl2and F2: Ruff (1928) obtained it by the direct combination of the elements at 250∘C in a copper tube.
(ii) It may also be prepared by the reaction of Cl2 with HF or CF3.
(i) It is a colourless gas of characteristic smell. It can be liquefied and solidified only at low temperatures.
(ii) Its m.p. is −155.6∘C and b.p. is 100.1∘C
(iii) it dissociates on heating.
(iv) It combines with carbon monoxide to form carbonyl chloro fluoride.