Skip to content

Steric effect

What is the steric effect?

  • Steric effect is the spatial interaction (non-bonding) due to spatial crowding of bulky groups in a molecule , which affects their stability, properties and reaction rate.
  • Steric effect is one of the factor which affects the stability of a molecule.
  • The stability of bulky groups decreases due to the repulsion caused by the steric effect.
  • It causes obstruction to the attacking agent known as steric hindrance.

Steric effect

Applications of steric effect

1. Stability

(a) Trans-but-2-ene and cis-but-2-ene

In cis isomer, bulky methyl groups are close by and have steric repulsion, so they are less stable. But in trans, methyl groups being on opposite side are far away from each other so that there is no steric repulsion and hence more stable.

Steric effect

(b) Conformational isomers of butane

  • Anti form is most stable since two methyl groups are on opposite side..
  • The repulsion of the bulky groups causes the fully eclipsed form to be the least stable.

conformational isomers showing steric effect

2. Basicity of amines

  • Unexpectedly lower basicity of tertiary amine is due to steric hindrance to the approach of H+ ions and also to the stabilization of the conjugate base through solvation.

basicity of amines showing steric effect

3. Acidity of carboxylic acid

In 2,6-di(t-butyl) benzoic acid, since there is steric hindrance to the stabilization of carboxylate ion through solvation, it is less acidic than benzoic acid.

benzoic acid is more acidic due to no steric hindrance
Benzoic acid
2,6-di(t-butyl) benzoic acid is less acidic due to the steric hindrance
2,6-di(t-butyl) benzoic acid

4. Reactivity

(a) SN2 reactivity of alkyl halides

SN2 reactivity of tertiary halides is least because of steric hindrance.

SN2 reactivity of alkyl halides due to steric effect

(b) Rate of esterification of carboxylic acid

Steric hindrance to the approach of alcohol to the reaction site on carboxylic acid will lower the rate of esterification.

Benzoic acid gives esterification due to no steric hindrance

2,4,6-trimethyl benzoic acid gives no esterifcation due to the presence of steric hindrance

Order of esterification rate carboxylic acid due to the steric effect

 

Recommended video

 

 

1 thought on “Steric effect”

  1. Pingback: Cannizzaro Reaction - Chemistwizards

Leave a Reply

Your email address will not be published. Required fields are marked *

Verified by MonsterInsights