Question bank/JEE Main/Chemistry
JEE MainChemistryModerateOrganic Chemistry
Which one of the following is least reactive in a nucleophilic
substitution reaction?
Show answer and solution
The non reactivity of the chlorine atom in vinyl chloride may
be explained from the molecular orbital point of view as follows. If the
chlorine atom has sp^2 hybridization the C -Cl bond will be a σ bond
and the two lone pairs of electron would occupy the other two
[IMAGE] orbitals. This would leave a p -orbital
containing a lone pair and this orbital could not conjugate with the π
bond of the ethylenic link. Thus two M.O.S. will be required to
accommodate these four π electrons. Furthermore since chlorine is more
electronegative than carbon, the electron will tend to be found in the
chlorine atom has now lost full control of the one pair and so, is less
negative than it would have been had there been no conjugation. Since
two carbon atoms have acquired a share in the lone pair, each atom
acquires a small negative charge. Hence, owing to delocalization of
bonds (through conjugation), the vinyl chloride molecule has an
increased stability. Before the chlorine atom can be displaced by some
other group the lone pair must be localized again on the chlorine atom.
This requires energy and so the chlorine is more firmly bound than has
no conjugation occurred.
be explained from the molecular orbital point of view as follows. If the
chlorine atom has sp^2 hybridization the C -Cl bond will be a σ bond
and the two lone pairs of electron would occupy the other two
[IMAGE] orbitals. This would leave a p -orbital
containing a lone pair and this orbital could not conjugate with the π
bond of the ethylenic link. Thus two M.O.S. will be required to
accommodate these four π electrons. Furthermore since chlorine is more
electronegative than carbon, the electron will tend to be found in the
chlorine atom has now lost full control of the one pair and so, is less
negative than it would have been had there been no conjugation. Since
two carbon atoms have acquired a share in the lone pair, each atom
acquires a small negative charge. Hence, owing to delocalization of
bonds (through conjugation), the vinyl chloride molecule has an
increased stability. Before the chlorine atom can be displaced by some
other group the lone pair must be localized again on the chlorine atom.
This requires energy and so the chlorine is more firmly bound than has
no conjugation occurred.
Source: Grass-G / CH-10 Chemistry Paper-1 30 Oct New Jee main.docx
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