Tautomerism is not shown by:

• A. CH₃NO₂
• B. C₆H₅COCH₃
• C. (CH₃)₂C = N - OH
• D. C₆H₅CHO

Tautomerism is a chemical phenomenon where compounds can exist in two interconvertible forms, typically involving the relocation of a hydrogen atom and a double bond. In the options provided, we need to identify which compound does not exhibit this behavior.

Analyzing the Options

• CH₃NO₂: This compound can show tautomerism due to the presence of a nitro group that can participate in hydrogen transfer.
• C₆H₅COCH₃: This ketone can also exhibit tautomerism, particularly with its enol form.
• (CH₃)₂C = N - OH: This compound can undergo tautomerism as well, involving the shift of the hydrogen atom.
• C₆H₅CHO: Benzaldehyde does not show tautomerism because it lacks the necessary structural features for hydrogen transfer.

Final Answer

The compound that does not exhibit tautomerism is C₆H₅CHO (benzaldehyde).