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: typical reactions of alcohols (deprotonation, substitution, elimination, oxidation), rearrangements in organic chemistry, synthesis of ethers, reactivity of epoxides

Typical Reactions of Alcohols

Deprotonation of Alcohols

pKa of alcohols ~ 16-18 ⇒ strong bases are needed to deprotonate alcohols
Common strong bases: LDA, butyl lithium (BuLi), potassium hydride (KH)
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 Alkali metals can also deprotonate alcohols by reduction of H+
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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 and can be replaced with a better leaving group to favor SN reactions

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Mesyl Chloride CH3SO2Cl as a better leaving group:


 

Water as a better leaving group:

 

Carbocation Rearrangements - SN Reactions

During a SN1 reaction, a rearrangement of the secondary carbocation into a more stable tertiary can be observed. 2 rearrangements are possible: hydride shift or alkyl shift
 

Hydride shift:


 

Alkyl (CH3) shift:

Carbocation Rearrangements - E Reactions

During an E1 reaction, a rearrangement of the carbocation can be observed to favor the Zaitsev product (the most substituted alkene). 2 rearrangements are possible: hydride shift or alkyl shift
 

Hydride shift:

Same process with an alkyl shift

Ether Synthesis

Ether:

Class of organic compounds that contain an oxygen atom connected to two alkyl or aryl groups
Epoxide: cyclic ether with a three-atom ring
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Synthesis:

Linear and cyclic ethers by intramolecular SN reactions:


Epoxides by Williamson synthesis:

Reactivity of Epoxides


 

Mechanism of acid catalyzed ring opening: