Geometrical isomerism: cis- and trans-but-2-eneज्यामितीय समावयवता: समपक्ष और विपक्ष ब्यूट-2-ईन

NCERT Sec 9.3.3 · interactive diagram

Parts and their functions

• cis isomer (समपक्ष (cis) समावयव) — Similar groups (the two CH₃) on the same side of the double bond. The bond dipoles add up, so cis-but-2-ene is polar and boils higher (277 K).
• trans isomer (विपक्ष (trans) समावयव) — Similar groups on opposite sides. The dipoles cancel (μ ≈ 0), so it is non-polar with a lower b.p. (274 K), but it packs better in the solid, so its melting point is higher.
• Condition for cis–trans (cis–trans की शर्त) — The π bond does not allow free rotation about C=C, so the two arrangements are different compounds. Each double-bond carbon must carry two different groups — CH₂=CHCl or (CH₃)₂C=CH₂ show no geometrical isomerism.

Original diagram drawn by Simple Learning Hub, based on NCERT Sec 9.3.3. Report a mistake