Alcohols, Phenols and Ethers

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Alcohols, Phenols and Ethers
Fundamentals of General, organic and Biological
chemistry McMurry et al., 5ed, Prentice Hall
Alcohol and Phenols have OH group (hydroxyl
functionality). Polar. The presence of the
hydroxyl group makes them miscible with
water The OH group participates in
H-bonding Alcohols up to C5 are very soluble in
water. After that solubility decreases with
increasing number of Carbon atoms
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Alcohols
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Naming alcohols

• Start with the parent chain and replace the
  hydrocarbon e ending with ol
• Number the hydrocarbon chain. The carbon
  containing the OH group should
• have the lowest number
• Number the position of the OH group
• Number and name other side chains or
  functionalities using IUPAC rules

                                             
1-butanol
2-methyl-1-propanol
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Primary /secondary/tertiary
2-butanol A 2o alcohol (secondary)
2-methyl-2-propanol A 3o alcohol (tertiary)
                                        
                                 
1-propanol (1o alcohol)
Distinguish the difference between 1o, 2o and 3o
structures
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Nomenclature contd.
In a cyclic alcohol, it is understood that the
OH group is on C-1
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Alcohols
                                              
      
What is the identitity of this molecule?
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2-isopropyl-5-methylcyclohexanol

Menthol
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Alcohols (diols, triols)

• -diols or triols mean two or three hydroxy
  groups in the molecule
• Number the hydroxy group carbons with the lowest
  possible numbers
• Prefix uses the full parent name, i.e butane

                        ,
Ethane-1,2-diol (ethylene glycol)
Propane-1,2,3-triol (glycerol)
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Properties of alcohols

• Alcohols are polar compounds because the OH
  group participates in H-bonding
• Smaller straight chain alcohols are usually
  liquids
• Alcohols such as 1-heptanol (C8) tends to act
  more like alkanes
• Diols and triols have higher b.ps and are more
  water soluble

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Reactions of alcohols

• Dehydration Loss of water to form an alkene.
  Occurs in presence of acid catalyst
• Oxidation In presence of oxidizing agents
• alcohols get oxidized to carbonyl compounds

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Dehydration reaction
Fundamentals of General, organic and Biological
chemistry McMurry et al., 5ed, Prentice Hall
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Dehydration of alcohols
Hint- More substituted alkene will be major
product
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Dehydration of alcohols
Predict the starting alcohol in the following

?
?
Write all possible structures then keep the most
substituted ones!
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Oxidation
Note- Depending upon the alcohol and reaction
conditions a different types and mixtures of
carbonyl products may be formed
Image Adapted from http//www.chem.ucalgary.ca/cou
rses/351/Carey5th/Ch15/ch15-4-6.html
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Oxidation of alcohols
Secondary alcohols get converted to ketones upon
oxidation but no further
Q What is oxidation reaction for a tertiary
alcohol
Image Adapted from http//www.chem.ucalgary.ca/cou
rses/351/Carey5th/Ch15/ch15-4-6.html
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Oxidation of alcohols
?
?
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Hydroxybenzene (a.k.a Phenol)

• Have been used as an antiseptic
• Many OTC sore throat medications contain
  substituted phenols
• Most phenols are somewhat water soluble
• BHA and BHT are often used as food preservatives

BHA
BHT
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Acidity of phenols
Alcohols and Phenols are weakly acidic They
dissociate in water to give the alkoxide or the
phenoxide anion
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Phenols

• Methanol and Ethanols are as acidic as water, i.e
  weak acids,
• Ka 10-15
• Their anion (alkoxide ion) is a strong base,
  similar to the hydroxide
• ion
• Phenols are more acidic than alcohols
• Phenolic Ka is 1.0X 10-10