CBSE Class 12 Chemistry Notes: Haloalkanes – Physicsl Properties

1. Physical State, Colour, Odour:-

They are colourless when pure, methylchloride, ethyl chloride and some chlorofluoromethanes are gases at room tem.

Higher chlorobromo, iodo compounds are liquids or solids

2. Melting and Boiling Points:-

   i.   The boiling point and melting poils of chlorides and iodides are higher than those of hydrocarbons of comparable mass because of Polarity of bond.

 ii. For same halogen boiling points increases with increase in size alkyl group

Example:

CH₃Cl               CH₃CH₂Cl         CH₃(CH₂)₂Cl     CH₃(CH₂)₃Cl

249^oC               285.5^oC                        320^oC               351.5^oC

Physical Properties of Haloarenes:-

1. The b.p. of haloarenesare same as haloalkanes of same no. of 6 atom.
2. The melting and boiling points increases as the size of halogen atom increases

Iodoarenes > Bromoarenes > chloroarenes > Arenes

• 3. Dipole moments:-

    i. Haloalkanes:-

Dipole moment for them decrease as electronegativity of the halogen decrease form Cl to Br to I.

CH₃Cl(1.860D)> CH₃F(1.847D) > CH₃Br(1.830D)

  ii.Haloarens:-

Flcorobenzene(1.60D), chloro benzene(1.69D), and bromobenzene(1.70D) have lower Dipole moments than corresponding methyl halides.

4. Stability:-

Since the strength of C – X bond decreases in order C – F > C – Cl> C – Br > C – I therefore stability of alkyl halide is

Alkyl fluorides > Alkyl chlorides > Alkyl bromides > Alkyl iodides.

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