E1 REACTION (Part 1)

 E1 reaction, also known as Elimination-Unimolecular reaction, is a type of chemical reaction that involves the removal of a leaving group and a proton from adjacent carbon atoms in a molecule, resulting in the formation of a double bond.

The reaction mechanism involves a two-step process: in the first step, a leaving group departs from the molecule, generating a carbocation intermediate. In the second step, a proton is removed from an adjacent carbon atom, resulting in the formation of a double bond and the regeneration of a protonated leaving group.

E1 reactions typically occur in the presence of a strong base or heat, and they are most commonly observed in reactions involving secondary or tertiary alkyl halides. The rate of an E1 reaction depends only on the concentration of the substrate, as the reaction involves the formation of a carbocation intermediate that can be stabilized by neighboring groups.

Zaitsev and Hoffman products refer to two possible products that can be formed during an elimination reaction, particularly when a base is used to remove a proton from a beta-carbon atom in a molecule.

The Zaitsev product is the more stable and predominant product, which is formed when the elimination reaction occurs through the transition state that leads to the most substituted alkene. This product is also known as the "Saytzeff" product.

On the other hand, the Hoffman product is the less stable and less substituted product, which is formed when the elimination reaction occurs through the transition state that leads to the least substituted alkene. This product is also known as the "anti-Zaitsev" product.

The preference for the formation of Zaitsev or Hoffman products depends on the reaction conditions, the nature of the substrate, and the strength of the base used. Generally, Zaitsev products are favored in reactions involving strong bases and substrates that can stabilize the negative charge of the alkene intermediate through resonance or inductive effects. Meanwhile, Hoffman products are favored in reactions involving weaker bases or substrates that cannot stabilize the negative charge of the alkene intermediate.

It is important to note that while Zaitsev products are generally more stable and predominant, there are some instances where Hoffman products may be preferred, such as when steric hindrance around the beta-carbon atom makes it difficult for the base to approach and remove the proton from that position.

ANSWER (a)

Dehydration of Tertiary Alcohol

The dehydration of tertiary alcohols follows the E1 mechanism (elimination unimolecular), which involves the formation of a carbocation intermediate.

In the first step of the reaction, a proton from the beta-carbon adjacent to the hydroxyl group is removed by a strong acid, such as sulfuric acid (H₂SO₄) or phosphoric acid (H₃PO₄), resulting in the formation of a carbocation intermediate. Tertiary carbocations are relatively stable due to the presence of three alkyl groups that can stabilize the positive charge of the carbocation.

In the second step, a water molecule acts as a base and removes a proton from the beta-carbon, leading to the formation of a double bond and the release of a protonated water molecule (H3O+). The resulting product is an alkene, which is typically the major product of the reaction.

The (c) is the major product, (b) and (d) are the minor product. The (a) is not the product because the proton that has been remove is not in beta position. Furthermore, the hydride shift do not occur because its already tertiary carbocation.