2. BENZENE
Benzene is an organic chemical
compound with the molecular formula
C₆H₆. The benzene molecule is
composed of six carbon atoms joined in
a planar ring with one hydrogen atom
attached to each.
3. GENERAL PROPERTIES OF BENZENE
:-
Chemical formula :-C6H6
Appearance:-Colorless liquid
Odor:- Sweet aromatic
Melting point:-5.53 °C (41.95 °F;
278.68 K)
Boiling point:-80.1 °C (176.2 °F; 353.2 K
4. Discovery Of Benzene:-
*Benzene was first discovered by the English
scientist Michael Faraday from illuminating gas.(1825)
*The name benzene was given by German
Chemist Mitscherich in 1833.
*German chemists Joseph Loschmidt (in 1861)
and August Kekule von Stradonitz (in
1866) discovered its shape.
* American professor Linus Pauling proposed that
benzene exhibited a hybrid structure composed
of delocalized electrons.
5. STRUCTURE OF BENZENE:-
• Benzene is a closed ring of six carbon
atoms linked by bonds that alternate
between single and double bonds.
• According to MOT, benzene ring
involves the formation of three
delocalized π – orbitals spanning all six
carbon atoms, while the valence bond
theory describes two stable resonance
structures for the ring.
6. Resonance of Benzene:-
The oscillating double bonds in the benzene ring are
explained with the help of resonance structures as per
valence bond theory.
The hybrid structure is represented by inserting a
circle in the ring as shown below in the figure.(fig.was
proposed by kalke for benzene)
7. Aromaticity of Benzene:-
Benzene (aromatic compound) as the C-C
bonds formed in the ring are not exactly
single or double, rather they are of
intermediate length.
HUCKLE RULE :-
According to Huckel rule, for a ring to be aromatic it should
have the following property:
*Planarity
*Complete delocalization of the π electrons in the ring
*Presence of (4n + 2) π electrons in the ring where n is an
integer (n = 0, 1, 2, . . .) ..
