The hydrocarbon that cannot be prepared effectively by Wurtz reaction

Step-by-step solution

The Wurtz reaction 2R - X + 2Na dry ether R - R + 2NaX is effective only for symmetrical alkanes (even carbon count). Using two different alkyl halides gives a mixture of three products (R-R, R-R', R'-R'), making it ineffective for unsymmetrical alkanes. (1) 2,7-dimethyloctane: Symmetrical — can be split into two identical isopentyl fragments. Can be prepared effectively. (3) 1,4-dicyclohexylbutane: Symmetrical around the center. Can be prepared effectively. (4): Symmetrical structure with two identical cyclopentyl