Q76E - Organic Chemistry (Mcmurry)

Question

Each of the following reaction schemes contains one or more flaws.

What is wrong in each case? How would you correct each scheme?

(a)

(b)

(c)

Step-by-Step Solution

Answer

(a) Grignard reagent addition to a conjugated ketone yields the 1,2 product, not the 1,4 product. LiAlH₄ reduces a ketone to an alcohol. 

(b) Oxidation of alcohol with acidic CrO₃ converts primary alcohol to carboxylic acid, not an amine. 

(c) Treatment of cyanohydrin with H₃O⁺ produces a carboxylic acid, not an amine.

Step 1: Carbonyl Compounds

In organic compounds, a carbonyl group is a functional group composed of carbon atom double bonded to an oxygen atom (C=O).Aldehydes and ketones are called carbonyl compounds as they have carbonyl group (C=O) in their chemical composition, due to the electrophilic nature of carbonyl carbon, they are very reactive towards nucleophilic chemical species and give variety of reactions in order to form various chemical compounds like ester, acids alcohol etc.

Step 2: identify flaws in reaction (a)

(a) Grignard reagent addition to a conjugated ketone yields the 1,2 product, not the 1,4 product. LiAlH₄ reduces a ketone to an alcohol. The correct scheme:

                

                                    Correct scheme of reaction (a)

Step 3: identify flaws in reaction (b)

(b) Oxidation of alcohol with acidic CrO₃ converts primary alcohol to carboxylic acid, not an amine. The correct scheme:

                                     Correct scheme of reaction (b)

Step 4: identify flaws in reaction (c)

(c) Treatment of cyanohydrin with H₃O⁺ produces a carboxylic acid, not an amine. The correct scheme:

                                        Correct scheme of reaction (c)