Elimination with a small base

The base takes a hydrogen next to the leaving group. A small base reaches the more crowded position, so the more substituted alkene forms.

mechanism writtenBalanced: every atom is accounted for

What it needs, and what it gives

Reaction class: Elimination
Typical conditions: An alkoxide or hydroxide, warm. A bulky base gives the other alkene.
Mass balance: balanced — the co-products are written out, not dropped
Mechanism: Bimolecular elimination, one concerted step

Conditions are what the literature ordinarily uses, recorded so you can see whether yours are in the usual range. They are not a procedure and they are not scaled to your flask.

How it is thought to happen

One step. The base takes a hydrogen from one carbon while the leaving group departs from the next, and a double bond forms between them.

The base takes a hydrogen as the leaving group goes

This is the pathway taught for the class, not a record of what was observed. On the platform it is drawn on the structures you supply, with the curly arrows on the atoms that actually move.

Read the Bimolecular elimination mechanism

Try it on your own structures

Enter your reactants in the Reaction Lab. If this transformation matches what you drew, it is applied and the outcome is shown next to the records that back it — with the count of documented reactions doing the same thing on substrates like yours, rather than a confidence score.

Open the Reaction Lab Browse recorded reactions