Q21E - Organic Chemistry (Mcmurry)

Question

Draw the structure of the carbonyl compound(s) from which each of the following alcohols might have been prepared, and show the products you would obtain by treatment of each alcohol with (1) Na metal, (2) ${\mathbf{SOCl}}_{\mathbf{2}}$, and (3) Dess-Martin periodinane.

(a)

(b)

Step-by-Step Solution

Answer

Step 1: Reaction of alcohol

There are different types of reactions that can be observed with alcohols, such as converting alcohol to alkyl chloride using ${\mathbf{SOCl}}_{\mathbf{2}}$, converting alcohols to ketones using Dess-Martin periodinane, and alkoxide formation from alcohols by treating with Na metal. For the reduction of alcohols, the reagents used are ${\text{NaBH}}_{\text{4}}$and ${\text{LiAlH}}_{\text{4}}$.

Step 2: The products obtained

The given alcohol is (S)-5-Methyl-2-hexanol. It is obtained when 5-Methyl-hexan-2-one is treated with ${\text{NaBH}}_{\text{4}}$and ${\text{H}}_{\text{3}}{\text{O}}^{\text{ + }}$, the ketone group gets reduced to an alcohol.

Now, when (S)-5-Methyl-2-hexanol is treated with Na metal, alkoxide formation is seen.

When (S)-5-Methyl-2-hexanol is treated with ${\text{SOCl}}_{\text{2}}$, alkyl chloride is formed.

When (S)-5-Methyl-2-hexanol is treated withDess-Marin periodinane, oxidation of alcohol to ketone occurs.

The reduction product is a racemic mixture, and the reaction with (S) enantiomer is shown below,

Products obtained when (S)-5-Methyl-2-hexanol is treated with Na metal, ${\text{SOCl}}_{\text{2}}$and Dess-Marin periodinane

Step 3: The products obtained by the treatment of (b) alcohol with (1) Na metal, (2) SOCl 2 ,and (3) Dess-Martin periodinane.

(a) The given alcohol is (S)-3-Methyl-1-pentanol. It is obtained when 3-Methyl-pentanal or 3-Methyl-pentanoic acid or 3-Methyl-pentanoate treated with ${\text{LiAlH}}_{\text{4}}$, and ${\text{H}}_{\text{3}}{\text{O}}^{\text{ + }}$, the aldehyde or carboxylic acid or ester group gets reduced to an alcohol.

Now, when (S)-3-Methyl-1-pentanol is treated with Na metal, alkoxide formation occurs.

When (S)-3-Methyl-1-pentanol is treated with ${\text{SOCl}}_{\text{2}}$, the product formed is alkyl chloride.

When (S)-3-Methyl-1-pentanol is treated withDess-Marin periodinane, oxidation of ${\text{CH}}_{\text{2}}\text{OH}$ to CHO group takes place.

The reduction product is a racemic mixture, and the reaction with (S) enantiomer is shown below[A1] ,

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Products obtained when (S)-3-Methyl-1-pentanol is treated with Na metal, and${\text{SOCl}}_{\text{2}}$ Dess-Marin periodinane