Oxidations of alcohols are their other, alternative, reactions. a. Possible oxid
ID: 480279 • Letter: O
Question
Oxidations of alcohols are their other, alternative, reactions. a. Possible oxidation outcomes vary by alcohol class (primary, secondary, ...). Describe the type of oxidation possible for each class, using examples b. Two special oxidation types are presented in Ch. 16. One is the biochemical oxidation process, in which alcohol hydroxyls become carbonyl groups. The other is the special oxidation of vicinal diols by periodic acid (per-eye-odic, not the word meaning something that happens from time to time;;-)). Show that reaction of a vicinal diol of your choice.Explanation / Answer
10a)
Primary alcohols can be oxidised to either aldehydes or carboxylic acids depending upon the choice of reagent.
With mild oxidising agents like PCC in non-aqueous media, primary alcohols are oxidised till aldehydes only,
CH3CH2OH ---------> (with PCC/CH2Cl2) CH3CHO
With stronger oxidising agent like KMnO4 or K2Cr2O7 in aqueous acidic medium , they are oxidised to carboxylic acids directly without isolation of aldehydes.
CH3CH2OH -------> (with KMNO4/H+) CH3COOH
Secondary alcohols are oxidised by KMnO4 or chromic acid to give ketones.
CH3CH(OH)CH3 ------> (with K2Cr2O7) CH3COCH3
Tertiary alcohols resist oxidation.
b) special oxidation of vicinal diols by periodic acid.
The vicinal diols undergo oxidative cleavage with periodic acid.Terminal CH2OH is oxidised to HCHO and middle CHOH are oxidised to HCOOH
CH2OH-CH2OH ------->(with HIO4) -----> 2 HCHO
CH3CHOH-CH2OH ------>(with HIO4) -----> CH3CHO + HCHO
CH2OH -CHOH-CH2OH ------>(with HIO4) -----> 2HCHO + HCOOH
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