1-chloro-4-nitrobenzene synthesis

[NA19]

The answer is A: Of the two substituents, the chloro group is para-directing, so it should be installed first, eliminating choices C and D. While HCl/H2O will add H/Cl across alkenes, these conditions will not substitute Cl in EAS reactions, eliminating Choice B. Also note that Na, NH3 results in the trans hydrogenation of alkenes but will not install a nitro group in an EAS reaction.

Okay, so my question is:

What does the Cl being para directing have to do with in being installed first? Can someone explain this question fully to me? The answer made no sense to me.

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[ashtonjam]

I'm 99% sure that EAS is not covered on the MCAT so it doesn't make a difference either way, but for curiosity's sake:

If you put on the nitro group first, it would direct meta since it's electron withdrawing. That would give you a 1,3 product instead. In addition, putting on the nitro group would make adding the chlorine really hard because the ring would be deactivated. So, two reasons.

Putting on chlorine first doesn't deactivate the ring and directs properly.

 

[sshah92]

Not on MCAT

 

[BerkReviewTeach]

Hasn't been on the MCAT since 2004. Please stop posting non-MCAT questions in the MCAT forum.

 

[NA19]

Really? This is from the TPR Science Workbook? So EAS is not on the MCAT at all?