 We know that phenols are more acidic than alcohols because on ionization, the phenoxyriene formed is much more stable than the alkoxyriene formed. As you can see here, the negative charge in the phenoxyriene is stabilized through resonance whereas no such resonance stabilization exists in the case of alkoxyriene. In fact, the electron donating alkyl group adds more electron density onto the oxygen atom and this decreases the polarity of the CO bond. And as a result, ionization is not favored in the case of alcohols. Alright, so that is something that we already know that phenols are more acidic than alcohols. Let's now go one step further and look at the effects of substituents on the acidic strength of phenols. How does the acidic strength vary if we have an electron donating or electron withdrawing group attached to our benzene ring? So let's explore that by solving a question. So the question is, is methanitrophinol more acidic than paranitrophinol? Okay, so here we have the substituent which is a strong electron withdrawing group, the nitro group and in one case we have the nitro group at the metaposition and in the other case we have it at the paraposition. So let's pause the video here and see if we can find out the answer to this question. Okay, now the clue is draw the resonance structures of the corresponding conjugate bases. Alright, so in single word the answer to this question is no, methanitrophinol is not more acidic than paranitrophinol. Now in this case you can see that the nitro group at the metaposition has no effect on stabilizing the negative charge but if you compare that with paranitrophinoxidion, in this case you can see that the electron withdrawing nitro group is effectively able to draw the electron density away from the benzene ring and even if you look at the resonance structures you can see that in the case of metanitrophinoxidion the negative charge is delocalizing onto the less electronegative carbon atoms right at the paraposition and at the autopositions. But in this case you can see that the negative charge delocalizes onto the more electronegative oxygen atom and this is why metanitrophinol is less acidic than paranitrophinol because the conjugate base is more stable in the case of paranitrophinol. Okay, so let's look at one more question. Here we need to figure out which among the two is most acidic. Now the most acidic molecule would be that which has the most stable conjugate base correct? So let's explore the stability of the conjugate base in both of these situations. Now if you look at the conjugate base formed here with paranitrophinol you can see that these are the resonance structures that are formed. Now methoxy group here is an electron donating group via resonance because the lone pair of electrons on the oxygen atom can delocalize with the pi electrons of the ring but as you can see here the electron donation is actually destabilizing the molecule especially if you look at this structure you can see that you have two negative charges very close proximity with each other this is very destabilizing and not just that because of this electron donation via plus r effect the CO bond polarity decreases and as a result it would not want to ionize and form protons. In other words the acidic strength decreases and if you contrast that with the conjugate base of paranitrophinol as we saw in the previous case we can see that the nitro group at the para position effectively draws the electron density away from the ring. It increases the polarity of the CO bond favoring more ionization and also it stabilizes the negative charge as the negative charge can delocalize onto the more electronegative oxygen atom. Now because the conjugate base of paranitrophinol is more stable than the conjugate base of paramethoxyphenol the most acidic molecule here would be paranitrophinol. So from here we have confirmed once again that the acidic strength depends on the stability of the conjugate base and if you go further and talk about the substituent effect electron donating group decreases the acidic strength by decreasing the polarity of the CO bond whereas electron withdrawing group increases the acidic strength by stabilizing the molecule and by making the CO bond more polar.