ZAISTAV vs HOFMANN ELIMINATION

zaistav elimination:

Normal elimination of alkyl halides (attacking of a base(nucleophile) on hydrogen instead of carbon) lead to form more substituted alkene as major product (Zaistav elimination product). The elimination proceeds by E1 or E2 mechanism.

Hofmann elimination:

Amines on exhaustive methylayion gives Quaternary ammonium salts which on treatment with moist silver oxide and on heating eliminates tertiary amine and forms less substituted alkene as the major product ( contrary to Zaistav product)

Explanation:

• For the Elimination(E2) of ''H'' and ''tertiary amine'' from quaternary ammonium salt , both should be anti-peri planar arrangement.
• In the Newmann projection to form more substituted alkene( Zaistav product) there is " Gauche interaction", which cause less stability. Hence less substituted alkene is the minor product.

• In the Newmann projection to form less substituted alkene (Hofmann product) there is no Gauche interaction between tertiary amine and hydrogen which is relatively more stable and E2 elimination leads to form Hofmann elimination product