Further Reactions of Alcohols and the Chemistry of Ethers | Organic Chemistry 1

The reactivity of alcohols and the chemistry of ethers are studied in this chapter: the typical reactions of alcohols (deprotonation, substitution, elimination, oxidation), the rearrangements in organic chemistry, the ethers synthesis, the reactivity of epoxides.

Typical Reactions of Alcohols

Deprotonation of Alcohols

Strong bases are needed to deprotonate alcohols.
Common strong bases: LDA, Butyl Lithium (BuLi), Potassium Hydride (KH).

 

 

 Alkali metals can also deprotonate alcohols by reduction of H+.

 

Substitution of Alcohols

One of the typical reactions of alcohols is the substitution of HO- by another chemical group.
This can lead to the synthesis of alkyl halides:
 


 

However, HO- is a bad leaving group.
We must modify it to favor SN reactions.

 

- Mesyl Chloride CH3SO2Cl as a good leaving group:


 

- Water as a good leaving group:

 

Carbocation Rearrangements - SN Reactions

Rearrangement of the secondary carbocation into the more stable tertiary one.
The rearrangement is only observed during a SN1 reaction.
2 rearrangements are possible: hydride shift or alkyl shift.
 

- Hydride shift:


 

- Alkyl shift:

Carbocation Rearrangements - E Reactions

The more substituted alkenes are preferred.
The rearrangement is only observed during a E1 reaction.
2 rearrangements are possible: hydride shift or alkyl shift.
 

- Hydride shift (same process with alkyl shift):

Ether Synthesis

Ether chemical function: R-O-R'.
Different synthesis methods depending on the desired ether (linear, cyclic or epoxide):

- Intramolecular SN reaction for linear and cyclic ethers

 


 

 

 - Williamson Synthesis for epoxides

 

Reactivity of Epoxides


 

Mechanism of acid catalyzed ring opening: