Stereoisomers from geometric and optical sources

Steps:

• Identify the double bond in each hex-2-ene for cis-trans (geometric) isomerism, requiring different substituents on each carbon.
• Check for chiral centers, needing four different substituents on a tetrahedral carbon.
• Calculate total stereoisomers: 2 per geometric isomer if present, times 2 per chiral center.
• Compare totals: A (1), B (2), C (4), D (2).

Why C is correct:

• 4-methylhex-2-ene has cis-trans isomerism at the double bond (different groups on C2 and C3) and one chiral center at C4 (attached to H, CH3, CH2CH3, CH=CHCH3), yielding 2 × 2 = 4 stereoisomers by the rule for independent stereogenic units.

Why the others are wrong:

• A: No cis-trans (C2 has two CH3 groups); no chiral centers; 1 stereoisomer.
• B: Cis-trans present; no chiral centers; 2 stereoisomers.
• D: Cis-trans present; C5 not chiral (two CH3 groups); 2 stereoisomers.

Final answer: C