Chapter 21, Problem 84A

Interpretation Introduction

Interpretation:

The reason for the use of structural formula by chemists for organic compounds rather than molecular formula needs to be explained.

Concept introduction:

A scale model which represents the arrangement of atoms in the molecule is said to be molecular model.

Explanation of Solution

• Molecular formula: It represents chemical symbols of the elements in the molecule and the number of atoms of each element is represented by subscript.
• Structural formula: It consists of symbols of the elements and lines for the chemical bonds.

The reasons for the use of structural formula by chemists for organic compounds rather than molecular formula are:

• The identification of atoms and the structure of the compound is given by structural formula.
• The structures are not indicated by molecular formula, it helps in determining the exact number of atoms of every element present in the compound.
• The cause of reactivity of a compound can be explained from its structural formula.
• The reactive groups such as lone pairs, $\pi$-bonds etc. are included in the structural formula and not in the molecular formula.
• For a given molecular formula, there is a possibility of so many isomers. For example: for ${\text{C}}_{\text{5}}{\text{H}}_{\text{12}}$ there is in total 5 isomers (linear and branched chain) whereas from structural formula such confusion of isomers cannot exist.