Reactions of Alcohols,

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Chapter 12 Reactions of Alcohols, Ethers,
Epoxides, and Sulfur-Containing
Compounds Organometallic Compounds
Irene Lee Case Western Reserve University Clevelan
d, OH
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Reactions of Alcohols

• reaction with hydrogen halides
• acid-catalyzed dehydration (E1 Rxn)
• reaction with thionyl chloride
• reaction with phosphorous tribromide PCl3
• conversion to sulfonate esters

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Secondary and tertiary alcohols undergo SN1
reactions with hydrogen halides
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Primary alcohols undergo SN2 reactions with
hydrogen halides
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ZnCl2 can be used to catalyze certain SN2
reactions
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Rearrangement of secondary or tertiary alcohols
can occur in the SN1 reaction
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Amines do not undergo substitution reactions
because NH2 is a very strong base (a very poor
leaving group)
RCH2F gt RCH2OH gt RCH2NH2 HF H2O
NH3
pKa 3.2
pKa 15.7
pKa 36
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Other Methods for Converting Alcohols into Alkyl
Halides
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Activation by SOCl2
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Converting Alcohols into Sulfonates (Excellent
Leaving Groups)
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Several sulfonyl chlorides are available to react
with -OH group
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SN2 Reactions of Activated Sulfonates
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Dehydration of Alcohols
To prevent the rehydration of the alkene product,
one needs to remove the product as it is formed
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Carbocation Rearrangement
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Ring Expansion
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Primary Alcohols Undergo Dehydration by an E2
Pathway
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Stereochemistry of the E1 Dehydration
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Milder Dehydration
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Substitution Reactions of Ethers
Activation of ether by protonation
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Reactions of Epoxides
Epoxides
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Nucleophilic attack of hydroxide ion on ethylene
oxide and on diethyl ether
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Ring Opening
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When a nucleophile attacks an unprotonated
epoxide, the reaction is a pure SN2 reaction
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Epoxides Are Synthetically Useful Reagents
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Crown Ethers
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A crown ether specifically binds certain metal
ions or organic molecules to form a hostguest
complex, an example of molecular recognition
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Thiols are sulfur analogs of alcohols
ethanethiol
1-propanethiol
2-mercaptoethanol
3-methyl-1-butanethiol
They are stronger acids (pKa 10) than alcohols,
but do not exhibit hydrogen-binding
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In protic solvent, thiolate ions are better
nucleophiles than alkoxide ions
CH3OH
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The sulfur analogs of ethers are called sulfides
or thioethers
Sulfur is an excellent nucleophile because its
electron cloud is polarized
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Organometallic Compounds
An organic compound containing a carbonmetal bond
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Preparation of Organolithium Compounds
hexane
1-bromobutane
butyllithium
hexane
phenyllithium
chlorobenzene
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Preparation of Organomagnesium Compounds
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Alkyl halides, vinyl halides, and aryl halides
can all be used to form organolithium and
organomagnesium compounds
However, these organometallic compounds cannot be
prepared from compounds containing acidic groups
(OH, NH2, NHR, SH, CCH, CO2H)
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Coupling Reactions
Formation of carboncarbon bonds
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