Inductive Effect: The inductive effect refers to the polarity produced in a molecule as a result of higher electronegativity of one atom compared to another.Atoms or groups which lose electron towards a carbon atom are said to have +1 Effect. Those atoms or groups which draw electron away from a carbon atom are said to have -I Effect. Common examples of -I effect are: NO
2, F, Cl, Br, I, OH etc. Examples of +1 effect are (Electron releasing) (CH
3)
2C- , (CH
3)
2CH-, CH
3CH
2- CH
3- etc.
Electromeric effect: The electromeric effect refers to the polarity produced in a multiple bonded compound as it is approached by a reagent.
The atom A has lost its share in the electron pair and B has gained this share. As a result A acquires a positive charge and B a negative charge. It is a temporary effect and takes place only in the presence of a reagent.
- -I-effect as shown below: As the number of halogen atoms decreases, the overall -I- effect decreases and the acid strength decreases accordingly.
- +I-effect as shown below: As the number of alkyl groups increases, the +I-effect increases and the acid strength decreases accordingly.
