Which of the given sequences helps convert pentane-1,5-dioic acid to heptane-1,7-dioic acid?
1: LiAlH4 followed by work up;
3: KCN followed by H3O+
Start by reducing glutaric acid into its corresponding diol using LAH reduction and workup:
The diol is converted to its corresponding dibromoalkane using PBr3.
The bromide groups are displaced by cyanide via substitution.
The dinitrile on hydrolysis yields the required heptanedioic acid: