What is Q in the given reaction-

(A) Isobutane
(B) Isopropane
(C) Tertiary Butyl chloride
(D) Propane

Hint: The compound containing Magnesium is a Grignard reagent. The carbon attached to the magnesium metal will be nucleophilic in nature and will attack the more electrophilic atom of the other compound.

Complete step by step answer:
- In the above reaction we know that reactant A is Grignard reagent because it has the composition of RMgX.
- Grignard reagents are a group of reagents, which are generated by reacting organic halides and magnesium metal (Mg) mostly in the presence of ether. They have the general formula RMgX. R denotes an organic group (alkyl or alkenyl) while X represents a halogen. They are applied in the Grignard reaction.
- Now we will know about the Grignard reaction. Suppose we take any alcohol. Let us take R-OH, where R is an Alkyl group. We want to make this alcohol react with the Grignard Reagent (R’MgX).
- We have a nucleophile –R but unfortunately, we don't have any suitably electrophilic carbon. So, the nucleophilic alkyl group will attack on the hydrogen atom of hydroxyl group and will give an alkane as a final product. The final reaction can be given as below.

Thus, we can see that Propane will be formed at the end of this reaction with an organo-magnesium compound.

Hence option D is correct.

Note:
Remember that the nucleophilic carbon atom of Grignard reagent will not attack the carbon atom which is directly bonded to the hydroxyl group because C-O bond is strong enough that it cannot be broken by this reagent. When a Grignard reagent reacts with water, the same reaction occurs and it gives alkane as the product.