Haloalkanes and Haloarenes
Halogen Derivatives
Hydrocarbons are the parent of all organic compounds. When one or more hydrogen atoms of a hydrocarbon are replaced by halogen atoms, the compound becomes a halogen derivative.
Hydrocarbon and Haloalkane
In halogen derivative compounds, the halogen atom acts as a functional group. Halogen derivatives are classified as bromo, chloro, fluoro or iodo according to the type of halogen present.
Haloalkanes
The halogen derivatives of alkanes are called haloalkanes.
Haloalkanes
Chloroethane
2-Iodopropane
1-Bromo-1-iodoethane
Haloarenes
In haloarenes, the halogen atom is directly attached to an aromatic ring.
Haloarenes
Chlorobenzene
1,4-Dibromobenzene
2-Chlorotoluene
Halogen containing compounds are very useful in medical cares. For example, chloromycetin (a chlorine containing antibiotic) is used for the treatment of typhoid fever. Halothane (an anaesthetic agent) is used during surgery.
For more theory, please refer to Wikipedia.
Nature of the C-X Bond
The C-X bond (carbon-halogen bond) is polar because halogens are more electronegative than carbon atoms.
The strength of carbon-halogen bond decreases with the size of halogen atom due to increase in bond length and decrease in bond dissociation energy.
Strength of C−X bond → C−F > C−Cl > C−Br > C−I.
Nomenclature of Haloalkanes and Haloarenes.
Refer to nomenclature of haloalkanes and haloarenes. If you want to learn nomenclature from the very basics, refer to nomenclature introduction.
Questions
Question : Which of the following order regarding bond enthalpy ε(C−X) in an alkyl halide (RX) is
correct?
Answer : Bond enthalpy C−X (where X is Cl, Br, I) decreases with increase in atomic number of X.
Hence, the correct order is : ε(C−Cl) > ε(C−Br) > ε(C−I).