Question about DAT Bootcamp's QotD

[RamsFan1991]

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http://datquestionoftheday.com/category/organic-chemistry/

It says to rank the EAS functional substituents from most reacting to least. According to Chad from Chad's videos, the most donating to withdrawing would be -NR2, -OR, -CH3, Halogens, C double bond OR, then NO2 SO3H CN NR3 and CF3 equally withdrawing. Why is the answer choice A then? Thanks.

 

[CoFe2]

which part are you confused with? the answer coincides with what Chad says pretty much exactly.
The most reactive group is the NH2 group (same thing as NR2)
the second most reactive group is an OR group
The third most reactive is just a plain benzene ring because the other two groups are withdrawing so plain benzene is most reactive than those
the fourth most is the Ester.. Chad didn't really directly talk about these but it's reasonable to believe that it would be withdrawing but now quite as withdrawing as a carboxy acid (which should be somewhere near the end of your list)
and then the NO2 is the least reactive.

The only part that doesn't directly go with Chad is the ester but it's the only answer choice that put 3 and 4 first

 

[RamsFan1991]

how is NO2 the least reactive when Chad specifically put NR2 are the most donating/most reactive?

 

[Thanhn]

NR2 means 2 alkyl attached to the nitrogen. Alkyl groups are electron donating due to the hyperconjugation (s orbital) and the nitrogen also has a lone pair that will add to the benzene -- this means that NR2 groups are very activating/electron donating.

NO2 is O-N=O; (+) charge on nitrogen and (-) charge on an oxygen. This is deactivating because if you push the electrons around in the resonance forms, the benzene will get an overall positive charge. The oxygens in the -NO2 group can both have a negative charge in one of the resonance forms. This makes the NO2 very deactivating/electron withdrawing.

 

[RamsFan1991]

Thank you for explaining, makes much more sense.

 

[CoFe2]

ahh sorry I didn't realize that's where the confusion was coming from!