Q29E - Organic Chemistry (Mcmurry)

Question

Reduction of 2-butanone with NaBH₄ yields 2-butanol. Is the product chiral? Is it optically active? Explain.

Step-by-Step Solution

Answer

The reaction followed is shown below.:

Step 1: Reagent sodium borohydride (NaBH 4 )

The reducing reagent that is used to reduces the carbonyl group, ketone, and aldehyde to the primary alcohol, but this reagent is not used to reduce carboxylic acid and ester.

Step 2: Reagent sodium borohydride

2-butanone on reaction with sodium borohydride leads to the formation of the intermediate in which oxygen has the negative charge. This is followed by hydrolysis, oxygen gains the hydrogen and the formation of hydroxyl occurs.

Step 3: Chirality

The carbon is said to be chiral when all the surrounding atoms are different, and the chiral molecule is the active molecule, as shown below. Both the products are optical active because the carbon having a hydroxyl group is chiral. One bond is of hydrogen, the 2nd is methyl ring, the 3rd for another carbon, and the 4th for hydroxyl: