22 3 Summary of alkene hydration methods

Regiochemistry: Markovnikov addition.
Stereochemistry: No stereochemical control due to the formation of a carbocation intermediate.
Downside: Frequently leads to rearranged products due to carbocation stability.

Regiochemistry: Markovnikov addition product, similar to acid-catalyzed hydration.
Stereochemistry:
- Step 1: Anti-addition of OH and mercury complex.
- Step 2: Demercuration leads to a mixture of products; therefore, no control over stereochemistry.
Advantage: Seldom results in rearranged products, providing good regioselectivity.

Regiochemistry: Anti-Markovnikov addition product.
Stereochemistry: Very good stereospecific control, with syn addition of H and OH.
Advantage: Seldom sees rearrangements, making it highly reliable for anti-Markovnikov additions.

Process:
- Involves carbocation formation, which undergoes rearrangement to a more stable tertiary carbocation.
- Final product results from nucleophile attack on the stable carbocation, leading to rearrangements.

Process:
- Produces Markovnikov addition without rearrangement.
- Generates a more substituted alcohol directly from the reaction set.

Process:
- Results in the formation of a less substituted alcohol through anti-Markovnikov addition.
- The addition of H and OH occurs syn, on the same face of the double bond.

Methods for Generating Alcohols from Alkenes

Regiochemistry: This method follows Markovnikov's rule, leading to the addition of water across the double bond such that the more substituted carbon receives the hydroxyl (OH) group.
Stereochemistry: There is no stereochemical control during this process due to the formation of a carbocation intermediate.
Downside: The carbocation can rearrange to form a more stable species, which often results in a mixture of products, including unexpected rearranged compounds. This limits the predictability of the product distribution and can complicate product purification.

Regiochemistry: This approach also leads to a Markovnikov addition of water, similar to acid-catalyzed hydration, ensuring the more substituted carbon ends with the -OH group.
Stereochemistry: The process consists of two main steps:
- Step 1: An anti-addition occurs where the mercury compound adds to the alkene, forming a mercurinium ion, which results in anti addition of -OH and -Hg.
- Step 2: Demercuration takes place, leading to a mixture of alcohol products; hence, there is no control over the stereochemical outcome.
Advantage: This method rarely results in rearrangements, offering good regioselectivity and resulting in product yields that are more straightforward to optimize than with other methods.

Regiochemistry: This reaction results in the anti-Markovnikov addition of water, meaning that the hydroxyl group ends up at the less substituted carbon, which is beneficial in the synthesis of certain products.
Stereochemistry: Hydroboration provides excellent stereospecific control as it involves syn addition (addition of -H and -OH occurs on the same side) across the double bond, preserving the stereochemistry of the alkene.
Advantage: This method seldom shows rearrangements, making it a reliable choice for producing anti-Markovnikov alcohols while avoiding the complications often associated with carbocations.

Process: In this method, the reaction begins with the formation of a carbocation when the alkene is protonated. This carbocation may undergo rearrangement to a more stable tertiary carbocation, which shifts the structure towards a preferred product. The nucleophile (water) then attacks the stable carbocation, resulting in a final product that can include additional rearranged versions, complicating the final mixture of products.

Process: The reaction first converts the alkene into a mercurium ion, which is then attacked by a nucleophile (water), yielding a Markovnikov addition product without rearrangement. This process directly generates a more substituted alcohol through a single, straightforward set of reactions, providing an effective synthetic route in organic chemistry.

Process: This two-step reaction commences with the addition of diborane to the alkene, resulting in the formation of a trialkyl borane intermediate. The subsequent oxidation step with hydrogen peroxide leads to the creation of a less substituted alcohol through anti-Markovnikov addition. Here, the concerted mechanism of addition ensures that the -H and -OH groups are added to the same side of the double bond, contributing to the retention of stereochemistry.