OrganicMediumNEET: 1-2 questions Q3D

Conformations of Ethane & Butane

Organic Chemistry — Some Basic Principles

Rotate the C–C single bond and watch 3D geometry, Newman projection, and torsional energy update in lockstep. Compare staggered vs eclipsed in ethane, and anti vs gauche vs eclipsed in butane.

Loading lab

Drag the slider to rotate the back carbon. The 3D molecule, Newman projection, and energy curve are all linked.

How to use this lab

1Ethane (C₂H₆) ya Butane (C₄H₁₀) choose karo.
2Dihedral angle slider drag karo — staggered ↔ eclipsed.
3Newman projection aur torsional energy curve saath update hote hain.

What you're seeing

C–C single bond ke around rotation hoti hai, lekin har angle equally stable nahi hota. Front aur back carbon ke H/CH₃ jab same side mein aate hain (eclipsed), electron clouds clash karte hain — energy badh jaati hai. Jab opposite sides mein hote hain (staggered), repulsion minimum — energy kam. Yeh chhota sa difference NEET mein bahut baar pucha jaata hai.

Key NEET facts

▸Ethane barrier: 12.5 kJ/mol — Eclipsed → Staggered energy gap. Small enough that rotation happens millions of times per second at room temp.
▸Butane: Anti vs Gauche: ≈ 3.8 kJ/mol — Anti is more stable — the two CH₃ groups are as far apart as possible (180°).
▸Butane: Fully eclipsed peak: ≈ 19 kJ/mol — Highest energy conformation — both CH₃ groups directly eclipse each other. Worst-case torsional + steric strain.

Memory trick

Stability order (butane): Anti > Gauche > CH₃–H eclipsed > CH₃–CH₃ eclipsed. Yaad rakho: methyls jitne door, utne khush.

Test Yourself

Which conformation of n-butane has the LOWEST potential energy?

Next lab

SN2 Reaction — Backside Attack & Walden Inversion

Haloalkanes & Haloarenes

→

Surgery · timed challenge

Learned it? Now prove it under the clock.

5 minutes · +4 right, −1 wrong (real NEET marking) · one global leaderboard.

Current #1 · Rudresh Singh · 444 marks

Take the challenge →

Built by Animesh Singh · @neetlab

🧭 How to use this lab

Learned it? Now prove it under the clock.

How to use this lab