Chapter 18, Problem 39PP

Interpretation Introduction

Interpretation For the given compounds, it should be predicted which compound will react most readily and least readily in an ${\text{S}}_{\text{N}}\text{1}$ process

Concept introduction:

• Unimolecular nucleophilic substitution reaction in organic chemistry is called ${\text{S}}_{\text{N}}\text{1}$ reaction.
• The first step of a ${\text{S}}_{\text{N}}\text{1}$ process is loss of leaving group, forming a carbocation.
• A five membered ring will be aromatic if it contains six $\text{π}$ electrons. In order to have six $\text{π}$ electrons, one of the carbon atoms must possess two electrons. It should be a carbanion.
• The conditions for aromatic compound are,

1. 1. 1. It should be planar
   2. 2. It must obey the Huckel’s rule

The requirement of an odd number of electron pair is called Huckel’s rule. A     compound can only be aromatic if the number of $\text{π}$ electron in the ring is 2, 6,10,14,18 and so on. This series of number can be expressed mathematically as $\text{4n+2}$, where n should be an integer and the compound is aromatic.

1. 3. Continuous conjugated $\text{π}$ system(all carbon should be in ${\text{sp}}^{\text{2}}$ hybridized state)

If any compound which doesn’t satisfy one of the above condition then the compound is not aromatic

• The conditions for anti-aromatic compound is

  It satisfy all the conditions except Huckel’s rule in the conditions of aromaticity

• Aromatic compounds are more stable than non-aromatic compound