The incorrect statement regarding the geometrical isomers of 2-butene is:

Step 1: Analyze each statement about 2-butene geometrical isomers

(a) Not interconvertible at room temperature — TRUE ✓ Interconversion requires breaking the $\pi$ bond (requires ~250 kJ/mol), which doesn't happen at room temperature.

(b) cis-2-butene has LESS dipole moment than trans-2-butene — FALSE ✗

• cis-2-butene: both $\ce{CH3}$ on same side → dipole moments add → $\mu > 0$
• trans-2-butene: $\ce{CH3}$ on opposite sides → dipole moments cancel → $\mu = 0$
• Therefore cis-2-butene has MORE (not less) dipole moment than trans-2-butene

(c) trans-2-butene is more stable — TRUE ✓ Trans isomers have less steric repulsion (bulky groups far apart) → more stable.

(d) They are stereoisomers — TRUE ✓ Geometrical isomers are a type of stereoisomer (same connectivity, different spatial arrangement).

Step 2: Identify the incorrect statement

Statement (b) is incorrect → Option (b)

Key Points to Remember:

• Dipole moment: cis > trans (for symmetric disubstituted alkenes)
• Stability: trans > cis (less steric strain)
• Boiling point: cis > trans (higher dipole → stronger intermolecular forces)
• Melting point: trans > cis (better crystal packing due to symmetry)