Question

Which one of the following compounds is most acidic? a- ClCH2CH2OH. b- phenol. c- Ortho nitro phenol. d- Ortho cerosol. Please explain it to me

Answer 1

c)Ortho nitro phenol

o-Nitrophenol is more acidic than o-cresol. It can be verified with the help of their pKa values. ... The greater acidic character of the first one can be explained on the basis of greater stability(or less basicity) of its conjugate base due to negative Inductive Effect and Delocalisation

The nitro-group is an electron-withdrawing group. The presence of this group in theortho or para position decreases the electron density in the O?H bond. As a result, it is easier to lose a proton. ... Hence, ortho and para nitrophenols are strongeracids than phenol.

And also we know that phenol is more acidic than alcohols like 2-chloroethanol(ClCH2CH2OH.) because it is very tough to remove the H ion from alcohol.Phenol can lose ion easily because phenoxide ion formed is stabilised to some extent,This is as the negative charge on the oxygen atom is delocalised around the ring i.e having a cyclic structure in phenol helps it stay stable even after hydrogen is removed.Delocalized charge means negative charge is distributed almost equally through the compounds.The more stable ion is,the more likely it is to form .In this case phenol,the alcohol is almost similar to being non charged even after the hydrogen ion is removed and thus can have some acidic effect.

So Ortho nitro phenol. is most acidic in the given compounds