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Chapter 10
STRUCTURE, SYNTHESIS AND REACTIONS OF ALCOHOLS AND
ETHERS
ORGANIC CHEMISTRY, 2ND EDITION PAULA YURKANIS BRUICE
RAED M. AL-ZOUBI, ASSISTANT PROFESSOR OF CHEMISTRY DEPARTMENT OF CHEMISTRY - N4L0
JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
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Structure of Alcohols
• Hydroxyl (-OH) functional group
• Oxygen is sp3 hybridized. =>
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Classification
• Primary: carbon with –OH is bonded to one other carbon.
• Secondary: carbon with –OH is bonded to two other carbons.
• Tertiary: carbon with –OH is bonded to three other carbons.
• Aromatic (phenol): –OH is bonded to a benzene ring. =>
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IUPAC Nomenclature
Steps:
1. Find the longest carbon chain containing the carbon with the -OH group.
2. Drop the -e from the alkane name, add -ol.
3. Number the chain, starting from the end closest to the -OH group.
4. Number and name all substituents.
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Hydroxy Substituent
• When -OH is part of a higher priority class of compound, it is named as hydroxy.
• Example:
4-hydroxybutanoic acid
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Naming Priority
• Acids
• Esters
• Aldehydes
• Ketones
• Alcohols
• Alkenes
• Alkynes
• Alkanes
• Ethers
• Halides
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Common Names
• Alcohol can be named as alkyl alcohol.
• Useful only for small alkyl groups.
• Examples:
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Naming Diols
• Two numbers are needed to locate the two -OH groups.
• Use -diol as suffix instead of -ol.
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Substitution Reactions of Alcohols
Alcohols and ethers have to be activated before they can undergo a substitution or an elimination reaction:
Convert the strongly basic leaving group (OH–) into the good leaving group, H2O (a weaker base):
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Primary, secondary, and tertiary alcohols all undergo nucleophilic substitution reactions with HI, HBr, and HCl: (SN1 or SN2 !!!!!!!)
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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:
Reaction carried out in 48% aqueous HBr. Recall that Br– is an excellent nucleophile in water.
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Dehydration of Secondary and Tertiary Alcohols by an E1 Pathway
To prevent the rehydration of the alkene product, one needs to remove the product as it is formed
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The major product is the most stable alkene product:
The most stable alkene product has the most stable transition state
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The rate of dehydration reflects the ease with which the carbocation is formed:
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Primary Alcohols Undergo Dehydration by an E2 Pathway
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The Stereochemical Outcome of the E1 Dehydration
(E or Z !!!!!)
Alcohols and ethers undergo SN1/E1 reactions unless they would have to form a primary carbocation
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Oxidation by Chromium (VI)
Oxidation of Alcohols
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Oxidation of Alcohols
Secondary alcohols are oxidized to ketones
Primary alcohols are oxidized to aldehydes and eventually carboxylic acids:
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A tertiary alcohol cannot be oxidized and is converted to a stable chromate ester instead:
No hydrogen on this carbon
PCC oxidizing agent oxidize primary alcohols to the
aldehyde
