Chapter 13, Problem 27P

Interpretation Introduction

Interpretation:

The reason behind hydrogens attached to third carbon in 1,4-pentadiene being more susceptible to abstraction by radicals is to be explained. Also, the reason behind hydrogens attached to third carbon in 1,4-pentadiene being more acidic than hydrogens attached to methyl group of propene is to be explained.

Concept introduction:

舧 Electrophiles are electron-deficient species, which has positive or partially positive charge. Lewis acids are electrophiles, which accept electron pair.

舧 Nucleophiles are electron-rich species, which has negative or partially negative charge. Lewis bases are nucleophiles, which donate electron pair.

舧 Free radical is an atom, molecule, or ion that has an unpaired electron, which makes it highly chemically reactive.

舧 Conjugated systems consist of a phenomenon known as conjugation, which can be defined as an interaction between p-orbitals with another across an intervening sigma bond. Conjugated systems, in simple words, can be represented as a system in organic compounds having alternate double bonds and single bonds.

舧 Delocalization of unpaired electrons results in more stability. Alkyl groups attached to the carbon atom having the positive charge or radical, helps in more stabilization of charge. Thus, tertiary carbocations or radicals are more stable than secondary and secondary carbocations are more stable than primary carbocations or radicals.

舧 Resonance is having 2 different shapes of a chemical entity but the change is only in the electron pair positions.

舧 Resonance enhances the acidity of the compound and makes it easier for the compound to give up protons. Higher resonant structures increase acidity of the compound.

The rules for drawing resonance structures are as follows:

舧 Only non-bonding electron pairs and pi electrons can participate in conjugation in the formation of various resonating structures.

舧 The single bonds present in the molecule do not break or form in the resonance structures.

舧 The placement of atoms present in the molecule remains fixed.

舧 The octet of all atoms is completely filled.

舧 More the number of resonance structures indicate higher stability of a compound.