Question

Which of the following compounds do not have sp$^3$ carbon atom(s)?
I. Acetone\quad II. Acetic acid\quad III. Buta-1,3-diene\quad IV. Propyne\quad V. Naphthalene

• A. I only
• B. II, III only
• C. IV, V only
• D. III, V only

Hint:

Look for single bonded C atoms to identify sp$^3$ hybridization.
Aromatic and conjugated systems typically contain sp$^2$ hybridized carbons.

Answer 1

The Correct Option is D

\begin{itemize} \item sp$^3$ carbon = carbon with four sigma bonds (single bonded). \item In Buta-1,3-diene (III), all carbon atoms are involved in double bonds or conjugation $\Rightarrow$ No sp$^3$ C. \item Naphthalene (V) is fully aromatic; all carbon atoms are sp$^2$ hybridized. \item Acetone (I), Acetic acid (II), and Propyne (IV) each contain at least one sp$^3$ hybridized carbon. \end{itemize}