Haloalkanes and Haloarenes
Physical and Chemical Properties of Haloalkanes
- Physical properties of Haloalkanes:
(a) Insoluble in water, though polar, because of being incapable of forming H-bond.
(b) Branches decrease boiling points.
- (c) Boiling point for same halogen increase in R group CH3Cl < CH3CH2Cl < CH3CH2CH2-Cl
(d) Boiling point increase for same alkyl group as I > Br > Cl > F
C2H5I > C2H5Br > C2H5Cl > C2H5F
(e) Density increases with increase in number of halogens and mass of halogen
C2H5I > C2H5Br > C2H5Cl > C2H5F ; CH3Cl > CH2Cl2 > CHCl3 > CCl4
(f) Dipole moment
CH3Cl (1.860D) > CH3F (1.847 D) > CH3Br (1.830D) > CH3I (1.636 D)
(g) Stability: RF > RBr > RCl > RI
(h) Alkyl iodides become dark due to the formation of I2
2RI → R − R + I2
- Some physical properties of haloarenes:
(a) Insoluble in water due to lack of formation of H-bond.
(b) Density and b.p. same as in case of haloalkanes.
(c) Dipole moment:
(d) O-Dichloro benzene has less dipole moment than the expected value because the steric effect of two Cl-atoms at -O- positions increases the bond angle than 60°.
(e) P-Dichloro benzene is used as antimoth compound and room freshener in ODONIL.
(f) Melting points: P-Dichloro benzene, because of best packing in solid state, among dichloro benzenes, has highest m.p 53°C and meta isomer the lowest 33°C, O-Dichloro benzene melts at 43°C
(g) Boiling points: O-Dichloro benzene (179°C) > para isomer (172°C) ≈ meta isomer.
View the Topic in this Video from 30:30 to 36:40
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