Question

Explain why methyl alcohol is soluble in water in all proportions, while stearyl alcohol [CH₃(CH₂)₁₆OH] is a waxy solid that is not soluble in water.

Short answer

Hydrophilic interactions predominate in methyl alcohol, and hydrophobic interactions predominate in stearyl alcohol. So,methyl alcohol is soluble in water in all proportions, while stearyl alcohol [CH₃(CH₂)₁₆OH] is a waxy solid that is not soluble in water.

Step-by-step solution

To explain the methyl alcohol is soluble in water in all proportion

The smaller alcohols (methyl alcohol) are soluble in water because they have a hydroxyl group. Hydroxyl groups can form hydrogen bonds with water molecules.

Alcohols with long carbon chains (stearyl alcohol) also can engage in favourable water-alcohol hydrogen bonds, but the difference is that the larger alcohols have larger nonpolar, hydrophobic regions in addition to their hydrophilic hydroxyl group.

When the hydrophobic effect overcomes the hydrophilic effect, water solubility is lost. This usually happens at about four or five carbons.

Hence Hydrophilic interactions predominate in methyl alcohol, and hydrophobic interactions predominate in stearyl alcohol.