Question

Which of the following are chiral molecules? I. Pentan-3-ol, II. 3-Methylheptane, III. 3-Bromo-3-methylpentane, IV. 3-Bromo-2-methylpentane

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

Hint:

Look for the carbon attached to 4 unique groups!

Answer 1

The Correct Option is B

Step 1: Rule for chirality.
A molecule is chiral when at least one carbon is bonded to four different groups. That carbon is called a chiral center. If any two groups on a carbon are the same, that carbon is not chiral.

Step 2: Check Pentan-3-ol (I).
The C3 carbon carries -OH, -H, and two ethyl groups. Two groups are identical (both ethyl), so it is not chiral.

Step 3: Check 3-Methylheptane (II).
The C3 carbon holds -H, -CH$_3$, an ethyl group, and a butyl group. All four are different, so this is chiral.

Step 4: Check 3-Bromo-3-methylpentane (III).
The C3 carbon holds -Br, -CH$_3$, and two ethyl groups. Two ethyls are the same, so it is not chiral.

Step 5: Check 3-Bromo-2-methylpentane (IV).
The C3 carbon holds -Br, -H, an ethyl group, and an isopropyl group. All four differ, so this is chiral.

Step 6: Collect the chiral ones.
Only II and IV have a chiral center.

Step 7: Conclusion.
So the answer is II, IV only. \[ \boxed{\text{II, IV only}} \]