Chapter 4, Problem 113CP

(a)

Interpretation Introduction

Interpretation: The Lewis structure of caffeine where all the atoms have a formal charge of zero is to be determined. The ${\text{sp}}^{\text{2}}{\text{,sp}}^{\text{3}}$ and the $\text{sp}$ hybridized carbon and nitrogen atoms are to be identified. The number of sigma $\left(\sigma \right)$ and pi $\left(\text{π}\right)$ bonds is to be calculated.

Concept introduction: The hybridization of an atom can be obtained by finding its steric number. The sum of the numbers of atoms bonded to the required atom and the number of lone pairs the atom has is known as the steric number.

If the steric number is $4$, the atom is ${\text{sp}}^{\text{3}}$ hybridized.

If the steric number is $3$, the atom is ${\text{sp}}^2$ hybridized.

If the steric number is $2$, the atom is $\text{sp}$ hybridized.

Sigma bonds are the single bonds present between atoms in a compound. The second bonding that occurs between the atoms is known as the pi bonding.

If the electrons present in all the chemical bonds are assumed to be equally shared among the atoms, then the charge assigned to the atom is known as the formal charge.

To determine: The Lewis structure of caffeine, the ${\text{sp}}^{\text{2}}{\text{,sp}}^{\text{3}}$ and the $\text{sp}$ hybridized carbon and nitrogen atoms and the number of sigma $\left(\sigma \right)$ and pi $\left(\text{π}\right)$ bonds.

(b)

Interpretation Introduction

To determine: The ${\text{sp}}^{\text{2}}{\text{,sp}}^{\text{3}}$ and the $\text{sp}$ hybridized carbon and nitrogen atoms.