Question

Tautomerism is exhibited by
A. ${{R}_{3}}CN{{O}_{2}}$
B. $RC{{H}_{2}}N{{O}_{2}}$
C. ${{(C{{H}_{3}})}_{3}}CNO$
D. ${{(C{{H}_{3}})}_{2}}NH$

Answer 1

Tautomerism is a phenomenon where a single chemical compound tends to exist in two or more interconvertible structures which are different in terms of the relative position of one atomic nucleus which is generally the hydrogen.

Complete Step by step solution: The two structures formed in the process of tautomerism are known as tautomers and these types of isomer compounds usually differ only in the number of electrons and protons. They also exist in dynamic equilibrium. When a reaction occurs between these compounds there is only transfer of protons. Tautomerism is also known by some other name called desmotropism. Tautomerism is generally the shifting of a hydrogen from one place to another by exchanging the covalent bond. There are many types of tautomerism like keto-enol, lactam-lactim etc. There is a very simple method of tautomerism which extracts the acidic hydrogen and undergoes through the process of resonance and during this process it adds the hydrogen to another place. So the basic condition for compounds to show tautomerism is that it must have acidic hydrogen and that will undergo resonance too. Out of all the given option $RC{{H}_{2}}N{{O}_{2}}$ is the only case which have acidic hydrogen and go through the resonance process while ${{(C{{H}_{3}})}_{2}}NH$ also have acidic hydrogen but it does not give resonance structures.

So from the above discussion we conclude that option B is the correct answer.

Note: Acidic hydrogen refers to term which has tendency to be released as ${{H}^{+}}$ ion and we can also explain it in another way that if any H-atom is attached to another atom or group of atoms with higher electronegativity than that H atom is also known as potential acidic hydrogen.