(De)Hydration, Oxymercuration & Hydroboration

Hydration Reaction

adding water (H₂O) across a double bond

Dehydration

going backwards from a hydration reaction, removing water. Dehydrations can happen in acidic conditions.

Hydride shift

A hydrogen moves with its two bonding electrons. (see image) The positive charge moves to a more substituted carbon. The goal is always: Make a more stable carbocation.

Migration

Sometimes there isn't a hydrogen that can move. Instead, an entire carbon group moves. CH3 moves to the neighboring carbon. The positive charge shifts to a more stable location.

Adding H₂O, H-OH

the same thing

Adding HX

Adding Hydrogen + a halogen.

Reagant

a chemical added to make a reaction happen.

Oxymercuration & Hydroboration

Both reactions turn an alkene into an alcohol. The only big difference is where the OH goes

Oxymercuration

1. Add Reagents: Hg(OAc)₂ & THF/H₂O

2. Add NaBH₄

The OH goes to the more substituted carbon (The carbon with the most carbons attached) (Major Product, Markovnikovs Product)

Hydroboration

1. Add Reagents: BH₃ & THF

2. then add H₂O₂/OH

OH goes to the less substituted carbon (The carbon with the least carbons attached)

This is called: Anti-Markovnikov (minor product)

H₂/Pt

makes an alkane

Hydrogen + Halogens

• HBr

• HCl

• HI

Hydration

H₂O/ H⁺ hydration —> alcohol (adding water to a double bond and making an alcohol).

Oxymercuration

Adding:

• Hg(OAc)₂, THF/H₂O

• and NaBH₄

Hydroboration

Adding:

• BH3, THF

• and H₂O₂/OH^-