A reaction A -> B -> C has an endothermic first step (Delta H = +20 kJ mol^-1) and a highly exothermic second step (Delta H = -60 kJ mol^-1). B is an intermediate lying higher than A and C. According to the Hammond postulate

the first transition state resembles A and the second resembles C

the first transition state resembles A and the second resembles B

the first transition state resembles B and the second resembles C

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A reaction $A B C$ has an endothermic first step ( $Δ H = + 20 kJ mo l^{- 1}$ ) and a highly exothermic second step ( $Δ H = - 60 kJ mo l^{- 1}$ ). B is an intermediate lying higher than A and C. According to the Hammond postulate

Athe first transition state resembles A and the second resembles C
Bthe first transition state resembles A and the second resembles B
Cboth transition states resemble the intermediate B
Dthe first transition state resembles B and the second resembles C

Answer: C

In step 1 the transition state is close in energy to B, because the step is endothermic. It is late and looks like B. In step 2 the step is strongly exothermic, so the transition state is close to its reactant B and is early. Thus both transition states resemble the intermediate B.

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A reaction A​B​C has an endothermic first step (ΔH=+20 kJ mol−1) and a highly exothermic second step (ΔH=−60 kJ mol−1). B is an intermediate lying higher than A and C. According to the Hammond postulate

Answer: C

More questions on Hammond postulate and reactivity-selectivity

A reaction $A B C$ has an endothermic first step ( $Δ H = + 20 kJ mo l^{- 1}$ ) and a highly exothermic second step ( $Δ H = - 60 kJ mo l^{- 1}$ ). B is an intermediate lying higher than A and C. According to the Hammond postulate