Provide an example of the Hoffmann and Saytzeff rules.

The Hoffmann and Saytzeff rules are two principles used in organic chemistry to predict the outcome of elimination reactions.

The Hoffmann rule states that in elimination reactions, the least substituted alkene is favored. This is because the transition state leading to the least substituted alkene has a lower energy barrier, making it more likely to occur. For example, in the reaction of 2-bromo-2-methylbutane with sodium ethoxide, the Hoffmann product (2-methyl-1-butene) is formed as the major product.

On the other hand, the Saytzeff rule states that in elimination reactions, the most substituted alkene is favored. This is because the more substituted alkene is more stable due to the increased number of alkyl groups attached to the double bond. For example, in the reaction of 2-bromo-2-methylbutane with potassium tert-butoxide, the Saytzeff product (2,3-dimethyl-1-butene) is formed as the major product.

The choice between the Hoffmann and Saytzeff products depends on the reaction conditions and the substrate being used. In general, reactions with strong bases and bulky substrates tend to favor the Hoffmann product, while reactions with weaker bases and less bulky substrates tend to favor the Saytzeff product. Understanding these rules can help predict the outcome of elimination reactions and aid in the synthesis of desired products.