Question

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

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

Hint:

Hybridization of carbon can be identified from the number of \(\sigma\)-bonds: \[ sp^3 \rightarrow 4 \sigma \text{ bonds} \] \[ sp^2 \rightarrow 3 \sigma \text{ bonds} \] \[ sp \rightarrow 2 \sigma \text{ bonds} \] Aromatic ring carbons and alkene carbons are generally \(sp^2\) hybridized.

Answer 1

The Correct Option is D

Step 1: Identify compounds with NO sp\(^3\) carbons.
sp\(^3\) carbon requires 4 single bonds (tetrahedral). Compounds with only sp or sp\(^2\) carbons have no sp\(^3\) carbon.

Step 2: Check each compound.
I (Acetone): CH\(_3\)-CO-CH\(_3\) -- the two CH\(_3\) carbons are sp\(^3\). II (Acetic acid): CH\(_3\)-COOH -- the CH\(_3\) carbon is sp\(^3\). III (Buta-1,3-diene): CH\(_2\)=CH-CH=CH\(_2\) -- all four carbons are sp\(^2\), no sp\(^3\). IV (Propyne): CH\(_3\)-C\(\equiv\)C-H -- the CH\(_3\) carbon is sp\(^3\). V (Naphthalene): all aromatic carbons are sp\(^2\), no sp\(^3\). Only III and V have no sp\(^3\) carbons. \[ oxed{III ext{ and } V} \]