Chapter 2, Problem 18PP

Interpretation Introduction

Interpretation:

The reaction between trimethyl amine and $\text{HCl}$ is to be shown and the expected hybridization state for the nitrogen atom in the product is to be predicted.

Concept Introduction:

▸ Lewis acids are electron pair acceptors.

▸ Lewis bases are electron pair donors.

▸ The valence shell electron pair repulsion (VSEPR) theory predicts the arrangement of atoms in molecules and ions.

▸ Amines are the organic compounds that contain an amino group $(-{\text{NH}}_2)$.

▸ They can act as nucleophiles and electrophiles in organic reactions.

▸ Amines can be classified into three categories: primary amines, secondary amines, and tertiary amines.

▸ If the nitrogen atom is directly attached to only one other carbon atom, the amine is a primary amine.

▸ If the nitrogen atom is directly attached to two other carbon atoms, the amine is a secondary amine.

▸ If the nitrogen atom is directly attached to three other carbon atoms, the amine is a tertiary amine.

▸ Higher the electron density around the nitrogen atom, more available is the electron pair to donate. Electron donors are Lewis bases.

▸ The reaction is Lewis acid- base reaction. The trimethyl amine donates a pair of electrons, so it acts as a Lewis base and $\text{HCl}$ accepts a pair of electrons, and so acts as a Lewis acid.

▸ Hybridization is the concept of mixing atomic orbitals into new hybrid orbitals which are suitable for pairing of electrons to form chemical bonds in valence bond theory.

▸ Hybrid orbitals are very useful in the explanation of molecular geometry.

▸ A trigonal planar geometry has $s{p}^2$ hybridization which has a bond angle of ${\text{120}}^{\text{o}}$.

▸ A tetrahedral geometry has $s{p}^3$ hybridization which has a bond angle of $\text{109}{\text{.5}}^{\text{o}}$.

▸ When one s-orbital and one p-orbital combine, it forms two $s{p}^3$ hybrid orbitals.

▸ When one s-orbital and two p-orbital combine, it forms three $s{p}^3$ hybrid orbitals.

▸ When one s-orbital and three p-orbital combine, it forms four $s{p}^3$ hybrid orbitals.