已知丙烷与Br
2发生一元取代反应的机理如下(R·、X·表示自由基):
(1)Br
2(g)→2Br·(g)ΔH
1 (2)CH
3CH
2CH
3(g)+Br·(g)→CH
3CH
2CH
2(g)+HBr(g)ΔH
2 CH3CH2CH3(g)+Br·(g)→CH3CHCH3(g)+HBr(g)ΔH2'
(3)CH
3CH
2CH
2(g)+Br·(g)→CH
3CH
2CH
2Br(g)ΔH
3 CH3CHCH3(g)+Br·(g)→CH3CHBrCH3(g)ΔH3'
其中,(2)是决定反应速率的关键步骤,其“能量-反应进程”如图所示。
下列说法错误的是( )