Compound ‘A’ undergoes following sequence of reactions to give compound ‘B’. The correct structure and chirality of compound ‘B’ is
[where Et is –C2H5]
[where Et is –C2H5]
The Correct Option is C
Approach Solution - 1
The problem involves a sequence of reactions that transform compound 'A' into compound 'B'. Let's analyze the steps to determine the structure and chirality of compound 'B'.
Step 1: Formation of Grignard Reagent
The first step involves the reaction of compound 'A' with magnesium (Mg) in the presence of diethyl ether (Et2O). This is a typical method to form a Grignard reagent. The bromine atom in compound 'A' is replaced by a magnesium-bromide (MgBr) unit:
Step 2: Reaction with D2O
In the second step, the Grignard reagent reacts with D2O (deuterium oxide). Grignard reagents are highly reactive with protic solvents like water and deuterium oxide. The deuterium from D2O replaces the magnesium-bromide group, resulting in the formation of a deuterated compound.
The overall reaction can be summarized as the introduction of a deuterium (D) atom in place of the bromine atom:
Conclusion: Structure and Chirality of Compound 'B'
Compound 'B' is a deuterated isobutane. The introduction of deuterium does not create a new chiral center; therefore, the compound remains achiral.
Out of the provided options, this analysis aligns with the option that shows isobutane with D in place of the Br group, having no chiral center.
Approach Solution -2
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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.