Chapter 22, Problem 73A

Interpretation Introduction

(a)

Interpretation:

The type of bond forms between −OH group of alcohol and water needs to be determined.

Concept introduction:

An organic compound can be soluble in water if it shows effective hydrogen bond formation with water molecules. The stronger is the interaction with water, more soluble is the compound.

Explanation of Solution

The bond formed between −OH group of alcohol and water is hydrogen bond. The hydrogen bond is formed between H atom (bonded with an electro negativity atom) and an electronegative atom in other molecule.

Interpretation Introduction

(b)

Interpretation:

A relationship between water solubility and alcohol size needs to be determined.

Concept introduction:

An organic compound can be soluble in water if it shows effective hydrogen bond formation with water molecules. The stronger is the interaction with water, more soluble is the compound.

Explanation of Solution

From the given table, it can be seen that from methanol to propanol, water solubility is infinite that means alcohol is completely soluble in water. As size of alcohol increases from butanol to heptanol, solubility in water decreases because it is 0.11, 0.030, 0.0058 and 0.0008 for butanol, pentanol, hexanol and heptanol respectively.

Interpretation Introduction

(c)

Interpretation:

An explanation for the relationship in part (b) needs to be provided.

Concept introduction:

An organic compound can be soluble in water if it shows effective hydrogen bond formation with water molecules. The stronger is the interaction with water, more soluble is the compound.

Explanation of Solution

If the carbon chain of an alcohol increases, its solubility in water decreases. Due to large number of carbon atoms in the carbon chain there is greater magnitude of dispersion forces between the chains. Therefore, more important intermolecular force is dispersion force in case of long carbon atom chain. This results in decrease in the solubility of higher alcohols in water.