INRODUCTION AND INDUCTIVE EFFECT
Dissociation of a Covlant Bond
- Reactions of Organic Compounds always involve the making and breaking of covalent bonds. \
- A Covalent Bond may break by two fundamentally different ways.
Hetrolytic Cleavage of Bond
- In Heterolytic Cleavage of bond, there is an unequal distribution of electrons. One atom gains both the electrons of the bond which makes the other atom lose them.
- This type of bond breaking is also called ionic cleavage.
- Positively charged carbon is called carbocation while the negatively charged carbon is called carbanion.
Homolytic Cleavage of Bond
- Bond cleavage in which equal distribution of electrons takes place during the chemical reaction is known as Homolytic Cleavage.
- This type of cleavage of bond also known as Homolysis produces neutral, unpaired electron species, known as free radicals.
Electronic Effect
The effects which appear due to electronic displacement of covalently bonded
electrons are known as Electronic Effects or Electron Displacement Effects.
Inductive Effect
- Polarization of sigma - bonded electrons either due to the electronegativity difference between the atoms forming the bond or/and due to the electronegativity difference between the atoms attached to these atoms when compared to atom.
- If an atom or group or ion pushes electrons away from itself when compared to atom then it is said to be exhibiting + effect.
- If an atom or group or ion pulls electrons towards itself when compared to atom then it is said to be exhibiting − effect.
- Lets check the inductive effect of −I group.
- Lets replace one of with another and then check.
- Increasing chain increases + effect but the rate of increase decreases.
- Lets replace one of with another and then one of with a .
- I effect decreases with distance.
- Lets replace the with a sp2 carbon.
- sp2 carbon has − I effect. So does sp carbon.
- Inductive effect is a particle effect. This means it is the manifestation of the particle nature of electrons.
- Inductive effect dissipates with distance.
- Inductive effect is a permanent effect.
- Inductive effect is a weak effect.
- Inductive effect is an ‘always’ effect.
- All negatively charged ions show + I effect.
- Negatively charged ions have greater + I effect than neutral atoms of groups.
- Among negatively charged ions + I effect decreases with increase of electronegativity.
- More the number of carbons in straight chain alkyl groups more is + I effect.
- For the same number of carbons in two different alkyl groups + I effect decreases with distance.
- +I effect increases with increase of mass of an isotope.
- Groups with complete positive charge or partial positive charge or those with electronegativity higher than show − effect.
- Groups with complete positive charge have greater − I effect than those with partial positive charge which have greater − effect than those without any charge. As ‘s-character’ of an atom increases its electronegativity increases which consequently increases its − effect. E.g. C (triple bond) C > C (Double Bond) C
- −I power: N(sp) > N(sp2 ) > C(sp) > N(sp3 ) > C(sp2)
