what is saytzeff's rule?

In dehydrogenation reaction (removal of Hydrogen and Halogen atoms) from alkyl halide,

• halogen atom is removed from alpha carbon (the carbon with with halogen is attached) and
• hydrogen is removed from beta carbon (the carbon attached to the alpha carbon directly) which is itself attached with more no. of alkyl groups.
• The product is alkene which has greater no. of alkyl groups attached to the doubly bonded carbon atoms.
• This is saytzeff rule.

Hence, 2-Bromopentane gives Pent-2-ene as the major product.

The second carbon from right is alpha carbon while 1st and 3rd is beta carbon. 3rd carbon is attached with other ethyl group (C-4 ), so hydrogen is removed from this to get alkene according to above said rule.