Question

The less reactivity of chlorine atom in \[{\rm{C}}{{\rm{H}}_{\rm{2}}} = {\rm{CH}} - {\rm{Cl}}\] is due to
A. Inductive effect
B. Resonance stabilisation
C. Electromeric effect
D. Electronegativity

Answer 1

Hint: Chlorine belongs to the group of halogens, that is, the 17th group. The reactivity of any halogen is dependent on the ability of the halogen to leave the compound. Here, we have to understand the C-Cl bond, to understand the reactivity of the Chlorine.

Complete Step by Step Solution:
Let’s discuss resonance stabilisation in detail. It describes an effect in which polarity results in a compound because of the interaction of a \[\pi \] bond and a lone pair or due to the interaction of two \[\pi \] bonds in neighbouring atoms. The resonance stabilisation of \[{\rm{C}}{{\rm{H}}_{\rm{2}}} = {\rm{CH}} - {\rm{Cl}}\]is shown as follows:

\[{\rm{C}}{{\rm{H}}_{\rm{2}}} = {\rm{CH}} - {\rm{Cl}} \rightleftharpoons {}^ - {\rm{C}}{{\rm{H}}_{\rm{2}}} - {\rm{CH}} = {\rm{C}}{{\rm{l}}^ + } \rightleftharpoons {}^ + {\rm{C}}{{\rm{H}}_{\rm{2}}} - {\rm{CH}} = {\rm{C}}{{\rm{l}}^ - }\]

Due to the resonance, the C-Cl bond acquires a double bond character. Therefore, Chlorine shows less electronegativity.

Hence, option B is right.

Additional Information: The inductive effect is the effect that happens due to the polarisation of a sigma bond (\[\sigma \]) because of the electron-donating effect of an adjacent group towards an electronegative atom. All the alkyl groups give the inductive effect. Electronegativity defines an atom's capacity to attract electrons to stabilise it. Fluorine has the highest electronegative character among all the halogens.

Note: It is to be noted that there is a difference between resonance and electromeric effect. The electromeric effect defines a complete shifting of pi electrons in the presence of a reagent. The nature of this effect is temporary. When the reagent is removed, the pi bond again gets reformed.