For any symmetric product of a Wurtz reaction, count the total number of carbons and divide by 2 to get the chain size of the reactant. The product has 12 carbons total, so reactant 'A' must have exactly 6 carbons. All options have 6 carbons, but splitting the structure evenly reveals a tertiary carbon attachment, pointing safely to option (A).
Step 1: Understand the reaction in the figure.
The figure shows an alkyl halide 'A' that is heated with sodium metal in dry ether. This setup is the famous Wurtz reaction. The single product made is the alkane named 3,4-diethyl-3,4-dimethylhexane. We must find 'A'.
Step 2: Know what the Wurtz reaction does.
In the Wurtz reaction two molecules of the same alkyl halide join together. Each molecule loses its halogen, and the two carbon pieces bond to each other.
\[ 2\,\text{R-X} + 2\text{Na} \rightarrow \text{R-R} + 2\text{NaX} \]
Step 3: Use the idea of cutting the product in half.
Since the product is R joined to R, it is made of two equal halves. So if we cut the product right at its central bond, each half tells us what R was.
Step 4: Draw the product chain.
The product 3,4-diethyl-3,4-dimethylhexane is:
\[ \text{CH}_3\text{-CH}_2\text{-C}(\text{CH}_3)(\text{C}_2\text{H}_5)\text{-C}(\text{CH}_3)(\text{C}_2\text{H}_5)\text{-CH}_2\text{-CH}_3 \]
The two middle carbons (C3 and C4) are identical and joined together, so this is our cutting point.
Step 5: Take one half and add the halogen back.
One half is the group $\text{CH}_3\text{-CH}_2\text{-C}(\text{CH}_3)(\text{C}_2\text{H}_5)\text{-}$. The halogen sat on this carbon before the reaction, so put a chlorine there:
\[ \text{CH}_3\text{-CH}_2\text{-CCl}(\text{CH}_3)\text{-CH}_2\text{-CH}_3 \]
Step 6: Name compound A.
The longest chain has 5 carbons, so it is a pentane. The chlorine and a methyl both sit on carbon 3. Naming alphabetically gives 3-Chloro-3-methylpentane, which is option 1.
\[ \boxed{\text{3-Chloro-3-methylpentane}} \]
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