Chemical propertiesDensity:Haloalkanes are generally more dense than the alkane they are derived from and
usually more dense than water. Density increases with the number of carbon and halogen
atom. It also increases with the increase in mass of halogen atom.
Solubility:The haloalkanes are only very slightly soluble in water, but dissolves in organic
solvents. This is because for dissolving haloalkanes in water the strong hydrogen bonds
present in the latter has to be broken. When dissolved in organic (non polar) solvents, the
intermolecular attractions are almost same as that being broken.
Bond Length:C—F < C—Cl < C—Br < C—I
bond length(pm)
C-F 138
C-Cl 177
C-Br 193
C-I 214Larger atoms means larger bond lengths, as the orbitals on the halogen is larger the heavier
the halogen is. In F, the orbitals used to make the bonds is 2s and 2p, in Cl, it’s 3s and 3p,
in Br, 4s and 4p, and in I, 5s and 5p. The larger the principal quantum number, the bigger
the orbital. This is somewhat offset by the larger effective nuclear charge, but not enough
to reverse the order.
44.3 Chemical properties
Bond strength:C—F > C—Cl > C—Br > C—I
bond strength(kJ mol-1)
C-F 484
C-Cl 338
C-Br 276
C-I 238The orbitals C uses to make bonds are 2s and 2p. The overlap integral is larger the closer
the principal quantum number of the orbitals is, so the overlap is larger in the bonds to
lighter halogens, making the bond formation energetically favorable.
Bond reactivity:C—F < C—Cl < C—Br < C—I
Stronger bonds are more difficult to break, making them less reactive. In addition, the
reactivity can also be determined by the stability of the corresponding anion formed in
solution. One of the many trends on the periodic table states that the largest atoms are
located on the bottom right corner, implying that iodine is the largest and fluorine being
the smallest. When fluorine leaves as fluoride (if it does) in the reaction, it is not so stable
compared to iodide. Because there are no resonance forms and inductive stabilizing effects