why the last one is the most basic?

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Fashionation

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pls check the attached picture.

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all of the other substituents are e- withdrawing thus stabilizing the conjugate base and making them less basic and the alkoxy group is e- donating which destabilizes the lone pair of the amino group and thus makes it more basic slightly

Right on with this one. If the stabilization is throwing you off, a quick rule to learn: The greater the amount of electron withdrawing groups on the ring, the less reactive it is toward electrophillic substitution (deactivating), and the more acidic the ring is. Now the reverse: The greater the amount of electron donating groups on the ring, the more reactive it is towards electrophillic substitution (activating), and the more basic the ring is.

In this problem, since we're looking for the most basic molecule we need to find the molecule with the greatest amount of electron donating groups, which explains your answer.
 
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sorry pls bear with my additional stupid question. Then how did you know Cl, NO2 are withdrawing while OCH3 is donating? Because O has extra electrons to share? So donating? while Cl needs extra-electron to stabilize? Then how about NO2? N has 2 lone pairs...
 
sorry pls bear with my additional stupid question. Then how did you know Cl, NO2 are withdrawing while OCH3 is donating? Because O has extra electrons to share? So donating? while Cl needs extra-electron to stabilize? Then how about NO2? N has 2 lone pairs...


the easiest way to deteremine if something is donating or withdrawing is if the atom attached to the ring has atoms attached to it that have lone pairs. for example no2 has two oxygens attached to it that have lone pair electrons. och3 does not have electron pairs. this is the easiest way for me to deteremine. this is an overall list found in your ochem books that would be really helpful. just remember withdrawing groups make the ring more acidic and donating groups make the ring more basic. just one of those things you have to memorize and practice. good luck
 
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