Concept Explanation: Periodate (HIO₄) Cleavage of Diols

Periodic acid (HIO₄) specifically cleaves vicinal diols (1,2-diols) where the two hydroxyl (-OH) groups are on adjacent carbon atoms. The reaction breaks the carbon-carbon bond between these carbons, oxidizing each carbon to carbonyl compounds (aldehydes or ketones).

Step 1: Identify Vicinal Diols - Check if the compound has two -OH groups on neighboring carbons.

Step 2: Apply HIO₄ Cleavage Rule - Only vicinal diols undergo cleavage. Non-vicinal diols (like 1,3-diols) or compounds without adjacent -OH groups are not cleaved.

Step 3: Evaluate Each Option:

Glycerol (HO-CH₂-CH(OH)-CH₂-OH): Contains vicinal diol (C1-C2) and cleavable by HIO₄.
Propan-1,2-diol (CH₃-CH(OH)-CH₂-OH): Vicinal diol (C1-C2) - cleavable.
1,3-Propanediol (HO-CH₂-CH₂-CH₂-OH): Non-vicinal (1,3-diol); -OH groups are separated by one carbon. Not cleaved by HIO₄.
Glycol (typically ethylene glycol, HO-CH₂-CH₂-OH): Vicinal diol - cleavable.

Final Answer: 1,3-Propanediol is not cleaved by HIO₄ because it lacks adjacent hydroxyl groups.

Related Topics

Oxidative Cleavage Reactions
Properties of Diols (Glycols)
Organic Oxidation Mechanisms

Key Formulae and Theory

General reaction for vicinal diol cleavage:

R - CH (OH) - CH (OH) - R^{'} \overset{HIO₄}{\to} R - CHO + R^{'} - CHO + {HIO}_{3} + H_{2} O

Theory: HIO₄ cleavage involves a cyclic periodate ester intermediate formed only when -OH groups are adjacent. This leads to C-C bond rupture. Non-vicinal diols cannot form this intermediate.