Question 56

The maximum number of RBr producing 2-methylbutane by above sequence of reactions is ________ -
(Consider the structural isomers only)

The reaction sequence shown is:

Formation of a Grignard reagent: $$RBr + Mg \xrightarrow{\text{dry ether}} RMgBr$$
Protonation (Hydrolysis): $$RMgBr + H_2O \rightarrow RH + Mg(OH)Br$$

Position 1 (Primary): Attachment at either of the two equivalent terminal methyl groups at the branched end.

Position 2 (Tertiary): Attachment at the central carbon atom.

Position 3 (Secondary): Attachment at the $$CH_2$$ group.

Resulting : 2-Bromo-3-methylbutane (or 2-bromo-2-methylbutane if numbered from the other side, but here it is a distinct environment).

Position 4 (Primary): Attachment at the terminal methyl group on the straight chain end.

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