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Why is p-nitrophenol more acidic (pKa=7.1) than o-nitrophenol (pKa=7.2) even though the nitro group is both an ortho-para directing group(deactivating) and electron withdrawing ???? Aieee comin close hurry up plssss.... Pls reply with the best soln as fast as possible !!! Always gonna be approved !!!

Geoffrey Richards , 14 Years ago

Grade 12

3 Answers

Gurwinder Kaur

In o-nitrophenol, there is intramolecular H-bonding b/w hydrogen and oxygen bcoz -NO2 group is very close to -OH group but in case of p-nirophenol there is no intramolecular H-bonding b/w hydrogen and oxygen bcoz -NO2 group is at opposite position to -OH group.So, proton can easily be released from p-nitrophenol.That is why p-nitrophenol is more acidic than o-nitrophenol.

Approved

Last Activity: 14 Years ago

Mukund jha

There can be two reasons behind this very first due to inter molecular hydrogen bonding and secondly there is minute change in ph values as on ortho position NO2 might create a ortho effect due to wich negative charge may not be able to do resonance with benzene ring hence less acidic than paranitrophenol

Last Activity: 9 Years ago

Mahanth

The pKa values of Ortho nitrophenol and para nitrophenol, illustrate that acidity will decrease, if the acidic hydrogen is involved in hyrogen bonding!

Last Activity: 8 Years ago