MolSynapsequestion bank

MolSynapse / Question bank / General Organic Chemistry II: Acids and Bases / Most acidic hydrogen in drawn molecules

JEE Advanced levelSingle correct optionDifficulty 3 of 3g2262

Which hydrogens of the compound shown are the most acidic?

Athe CH2 and N-H hydrogens are equally acidic
Bthe N-H hydrogens
Cnone, since there is no carboxylic acid group
Dthe CH2 hydrogens between the two carbonyl groups

Answer: D

The compound is barbituric acid. The CH2 hydrogens at C5 lie between two C=O groups; the enolate (equivalently the aromatic-like trione/enol anion) is strongly stabilised, giving pKa about 4.0. The imide N-H hydrogens (pKa above 10) are less acidic, a common error being to assume that N-H is more acidic than C-H.

Practice General Organic Chemistry II: Acids and Bases More on Most acidic hydrogen in drawn molecules

Previous questionNext question

More questions on Most acidic hydrogen in drawn molecules

Which hydrogen of the compound shown is the most acidic? NEET level
Which hydrogens of the compound shown are the most acidic? NEET level
The structures shown are four anions, each obtained from the molecule drawn by removing one proton. Which anion results from loss of the mos... JEE Main level
Which hydrogens of the compound shown are the most acidic? JEE Main level
The compound shown is a cyclic 1,3-diketone. Select ALL the correct statements. JEE Main level
Which hydrogen of the compound shown is the most acidic? JEE Main level