Inductive and Mesomeric Effects: Inductive Effect: Case of Chlorobactene

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Learning Outcomes

After studying this lesson, you shall be able to:

  • Inductive effect examples
  • Classify a group into or group

Inductive Effect

  • Let us consider the case of chlorobactene to understand this.
  • Here, acquires slight positive charge due to the electronegativity of which in turn acquires slight negative charge .
  • thus, becomes electron deficient and it exerts a pull on the electrons forming covalent bond between and but less strongly.
  • As a result, acquires a lesser positive charge as that on .
  • similarly acquires even lesser positive charge and so on.
  • Thus, a polarity is slowly induced throughout the carbon chain.
Inductive Effect
  • However, the effect is very less beyond carbon 3 or 4.
  • In other words, the effect diminishes as one moves further in the carbon chain relative to the position of the group.
  • The phenomenon of transmission of charge arising due to electronegativity difference in a covalent bond (i.e.. dipole) through a chain of carbon atoms linked by sigma bonds is called inductive effect.
  • Such an effect is therefore propagated in the entire chain of carbon atoms, which were otherwise non-polar (in the absence of group ) .
  • So, the atom/group responsible for the induction in polarity is .
  • Remember that group attracting electrons towards itself is normal due to the difference of electronegativity but induction of polarity in an otherwise non-polar bond due to the attachment of a more electronegative atom in the chain is known as inductive effect.
  • The atoms/groups like Cl which are more electronegative than carbon gain a slight negative charge on them and withdraw the electrons of the carbon chain towards themselves are known to exert -I Effect (pronounced as “minus I effect” )
  • Similarly, if a more electropositive group (say Y) is attached to an otherwise non-polar carbon chain, the group Y gets a fractional positive charge and the carbon linked to it gets a fractional negative charge.
  • This slightly electron rich carbon then acquires induced electropositive character and shares its excess electron density with the next carbon, which also acquires a fractional negative charge and so on.

e. g. Induced electronegative character

Inductive Effect
  • The atoms/groups which are more electropositive than carbon gain a slight positive charge on them and push the electrons of the carbon chain away from themselves are known to exert + I Effect (pronounced as “plus I effect” )
  • There are very few atoms or groups forming compounds with carbon which are more electropositive than carbon e. g. H and Mg.
  • However, the most important group exhibiting + I effect is the alkyl group, which due to a difference in electronegativities of hydrogen and carbon, makes the carbon slightly electron rich.

Inductive effect has the following characteristics:

1. It is a permanent effect.

2. It operates through sigma bonds. (Note that all the single, double and triple bonds have a sigma bond in them) .

3. Its magnitude goes on decreasing with increase in distance from the atom/group responsible for the same. Inductive effect is almost negligible after the third or fourth atom.

4. effect of some groups is in the order

+ I effect of some of the groups is in the following order:

Inductive effect is not a hypothetical phenomenon but is actually operative in the molecules. This has been demonstrated by the fact that it is commonly used to explain the properties like origin of dipole moment, increase or decrease in bond lengths, strength of acids or bases, etc.

MCQs

1. The slightly electron rich carbon acquires

a) Induced electronegative character

b) Induced electropositive character

c) becomes neutral

d) None of the above

Answer: B

2. In case of chlorobactene, acquires slight positive charge due to .

a) electronegativity of

b) electronegativity of

c) electro positivity of

d) All of the above

Answer: A

#Inductive effect examples

#Classify a group into or group

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