The structures of major products A , B and C in the following reaction are sequence
The structures of major products A , B and C in the following reaction are sequence
Show Hint
Pay attention to the reagents and reaction conditions to identify the type of reaction occurring in each step. \(LiAlH_{4}\) is a strong reducing agent, commonly used to reduce nitriles to amines.
The Correct Option is C
Solution and Explanation
Step 1: Reaction with\(NaHSO_{3}\) and Dilute HCl (Formation of A)
The starting compound is butan-2-one. The reaction with \(NaHSO_{3}\)followed by dilute HCl results in the formation of a cyanohydrin. The CN\(^-\) ion from NaCN attacks the carbonyl carbon, and the oxygen picks up a proton. The major product \(A\) is 2-hydroxy-2-methylbutanenitrile.
Step 2: Reduction with\(LiAl_{4}\) (Formation of B)
Lithium aluminum hydride \(LiAlH_{4}\)is a strong reducing agent. It reduces the nitrile group (CN) to an amine group \((NH_{2})\). The product \(B\) is 1-amino-2-methylbutan-2-ol.
Step 3: Hydrolysis with \(HCl/H_{2}O\) and Heat (Formation of C)
The amine group in \(B\) is hydrolyzed with \(HCl/H_{2}O\)and heat (\( \Delta \)) into a carboxylic group.
The major product \(C\) is 2-hydroxy-2-methylbutanoic acid.
Conclusion
The structures of \(A\), \(B\), and \(C\) correspond to option (4).
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Concepts Used:
Alkynes
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon-carbon triple bond. Alkynes are an organic molecule that contains triple bonds between the carbon atoms. Its general formula is CnH2n-2. They are also known as acetylenes. In this article, we will deal with the structure of alkynes.
Isomerism in Alkynes:
Alkynes show three types of isomerism
- Chain isomerism - Due to the different arrangement of carbon atoms in the chain that is straight chain or branched.
- Position isomerism - Due to the difference in the location of the triple bond.
- Functional isomerism - Isomeric with alkadienes both being represented by the general formula CnH2n-1.
Properties of Alkynes:
Physical Properties:
- Non-polar, unsaturated hydrocarbons.
- Highly soluble in organic and non-polar solvents and slightly soluble in polar solvents.
- High boiling point, in comparison to other hydrocarbons.
- Release a high amount of energy due to the repulsion of electrons in a reaction.
- More acidic than alkanes and alkenes due to SP hybridization.
Chemical Properties:
- Hydrogenation - Alkynes undergoes two types of hydrogenation reactions. Complete hydrogenation (in presence of Pd-C/ H2) and partial hydrogenation (in presence of Linder’s catalyst/H2).
- Act as a strong nucleophile by converting into acetylide.
- React with BH3 and undergo hydroboration reactions to form aldehydes and ketones.
- Undergo halogenation reactions in the presence of different halogenating agents by different mechanisms and forms haloalkanes.