Compound 'A' undergoes following sequence of reactions to give compound 'B'. The correct structure and chirality of…

Step 1: Grignard formation

Compound A (alkyl halide) + Mg in ether → Grignard reagent

$\ce{R-X + Mg ->[Et2O] R-MgX}$

Step 2: Reaction with D₂O

Grignard reagent + $\ce{D2O}$ (deuterium oxide) → deuteration

$\ce{R-MgX + D2O -> R-D + Mg(OD)X}$

The C-Mg bond is replaced by C-D bond.

Step 3: Determine structure of B

If compound A is: $\ce{R-CH2-X}$ (primary halide)

After Grignard + D₂O: $\ce{R-CH2-D}$ (deuterated alkane)

Step 4: Check for chirality

For compound B to be chiral, it must have a carbon with 4 different groups.

If the structure is: $\ce{R1-CHD-R2}$ where R1 ≠ R2

Then the carbon bearing D has:

• $\ce{-R1}$
• $\ce{-D}$
• $\ce{-H}$
• $\ce{-R2}$

All 4 different → Chiral ✓

Step 5: Match with options

Option (c) shows:

• Deuterated compound with D replacing H
• Chiral center present

Answer: (c)

Key Points:

Grignard reactions:

• $\ce{R-MgX + H2O -> R-H}$ (protonation)
• $\ce{R-MgX + D2O -> R-D}$ (deuteration)
• $\ce{R-MgX + CO2 -> R-COOH}$ (carboxylation)

Deuterium labeling:

• D (²H) is isotope of hydrogen
• Used as tracer in mechanism studies
• D and H are different for chirality

Chirality:

• Carbon with 4 different groups
• D ≠ H for chirality determination
• $\ce{C(R1)(R2)(H)(D)}$ is chiral if R1 ≠ R2