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Alcohols_ Phenols_ Ethers.ppt

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					Alcohols, Phenols, & Ethers

         Chapter 13
              Introduction
• Hydroxy groups: –OH functional group
  – Alcohol – has an –OH group attached to an
    aliphatic cation. General formula R-OH
  – Phenol – has an –OH group on a benzene
    ring


• Ether – a compound that has the
  functional group
                        Alcohols
Structure, nomenclature, physical properties, preparation, chemical
             reactions, mechanisms and synthesis.

At the end of this section, you should be able to:

1. Give the general structure of an alcohol.
2. Name alcohols by the IUPAC system.
3. Draw structures corresponding to IUPAC names of given
   alcohols.
4. Predict relative acidities of molecules.
5. Synthesize alcohols.
6. Predict products of reactions involving alcohols.
7. Formulate the mechanisms of reactions involving alcohols.
8. Explain how the Lucas test is used to distinguish between
   primary, secondary and tertiary alcohols.
9. Explain the anti-Markovnikov's addition of water via
   hydroboration.
          Important Alcohols
• Methanol (wood alcohol): CH3OH
                          catalysts

  – Production: CO + 2H2     →         CH3 – OH
                          heat, pressure

  – Useful as a solvent and industrial starting
    material.
  – Highly toxic, causes blindness and/or death.
     Important Alcohols cont.
• Ethanol (ethyl alcohol, grain alcohol)
  CH3CH2OH.
  – Produced commercially from ethylene and
    through biological (yeast) fermentation of
    carbohydrates.
  – Useful as a solvent, industrial starting
    material, fuel (gasohol) and found in alcoholic
    beverages
  – Moderately toxic.
                      Alcohol Overdose
       http://www.alcohol-treatment-info.com/What_To_Do_in_the_Event_of_Alcohol_Overdose.html




• http://www.thehealthcarenet.com/IMAGES/ACC_Alcohol.jpg
       Important Alcohols cont.
• 2-propanol (isopropyl alcohol) is the main
  component of rubbing alcohol

• 1,2,3-propanetriol (glycerol) is used as a food
  moistening agent (nontoxic) and for its soothing
  qualities (soaps)
             Triglycerides
• An example of the esterification process
  with glycerol and a fatty acid
     Important Alcohols cont.
• Antifreezes
  1,2-ethanediol (ethylene glycol).




 1,2-propanediol (propylene glycol).
           Fat and Cholesterol
                                  Squalene
• Trans and saturated fats are
  correlated with heart
  disease.
• Linked to high cholesterol
  level.
• Cholesterol is rigid
• Squalene is a precursor to
  steroid formation. All higher
  organisms produce
  squalene. It is a key
  intermediate in the
  biosynthesis of cholesterol.
             Naming Alcohols
• Step 1: Name the longest chain to which the –OH group
  is attached. Use the alkane name of the chain, drop the
  –e ending, and replace it with –ol.
• Step 2: Number the longest chain to give the lowest
  number to the carbon with the –OH
• Step 3: Locate the –OH position


Example:
       Naming Alcohols cont.
• Step 4: Locate and name any other groups
  attached to the longest chain.
• Step 5: Combine the name and location of other
  groups, the location of the –OH, and the longest
  chain into the final name.


Example:
Classification of Alcohols
Physical Properties of Alcohols
• The –OH group is polar and capable of
  hydrogen bonding.
  – This makes low molecular weight alcohols
    highly soluble in water.
  – Hydrogen bonding in a water – methanol
    solution
   Physical Properties of Alcohols
               cont.
• Larger alkanes have greater hydrophobic
  regions and are less soluble or insoluble in
  water.
  – Water interacts only with the –OH group of 1-
    heptanol.
  Physical Properties of Alcohols
              cont.
• The –OH group can hydrogen bond
  between alcohol molecules leading to
  relatively high boiling points.
  – Hydrogen bonding in pure ethanol;
          Alcohol Reactions
• The removal of water (dehydration) from
  an alcohol is an elimination reaction and
  produces and alkene.
      Alcohol Reactions cont.
• Under slightly different conditions, a
  dehydration reaction can occur between
  two alcohol molecules to produce an ether.
      Alcohol Reactions cont.
• Oxidation – the removal of hydrogen atoms.
  – Alcohol oxidations with an oxidizing (O) agent:
     • Primary alcohols →aldehyde → carboxylic acid.
     • Secondary alcohols → ketone.
     • Tertiary alcohols → no reaction.
      Alcohol Reactions cont.
• Primary alcohol oxidation




• Secondary alcohol oxidation
                Phenols
• Phenol behaves as a weak acid in water




• And can react with bases to form salt.
             Phenols cont.

• Phenols are slightly acidic because the
  aromatic ring stabilizes the phenoxide ion.
  Aliphatic alcohols do not have stabilizers.
                Phenols cont.
• In benzene, the six p orbital bonding electrons of
  the sp2 hybridized carbon atoms can move freely
  around the ring.
  A hybrid orbital view of the benzene structure
             Uses of Phenols
• In a dilute solution, phenol is a disinfectant.

  Phenol derivatives used as disinfectants
      0-phenylphenol
      2-benzyl-4-chlorophenol


• Phenol derivatives used as antioxidants in food
     BHA (butylated hydroxy anisole)
     BHT (butylated hydroxy toluene)
                  Ethers
• Naming ethers – the –O-R group is called an
  alkoxy group. The –yl ending of the smaller
  R group is replaced by –oxy.
              Cyclic Ethers
• Heterocyclic rings contain atoms other than
  carbon in the ring.
         Properties of Ethers
• Much less polar than alcohols.
• More soluble in water than alkanes, but less
  soluble than alcohols.
• Low boiling and melting points because of the
  inability to hydrogen bond between
  molecules.
    Properties of Ethers cont.
• Hydrogen bonding of dimethyl ether:
  (a) with water and      (b) no hydrogen
                              bonding in the
                              pure state:
           Ether Reactions
• Like alkanes, ethers are inert and do not
  react with most reagents.
• Also like alkanes, they are highly
  flammable.
 Thiols: the –SH (sulfhydryl) group
• Most distinguishing characteristic is their
  strong and offensive odor.
  – Ethanethiol – added to natural gas.
  – 1–propanethiol – odor in garlic and onions.
  – Trans –2 –butene–1 –thiol – odor associated
    with skunks
           Thiol Reactions
• Oxidation forms disulfide (-S-S-) linkages
  which are important structural features of
  some proteins.

 2R–SH + M2+ → R–S–M–S–R + 2H+
        Thiol Reactions cont.
• Oxidation reactions can be reversed with a
  reducing agent (H).
     R–S–S–R +2(H) → 2R–SH

• Reacts with heavy metals (Pb2+, Hg2+) to form
  insoluble compounds, with adverse biological
  results.
     2R–SH + M2+ → R–S–M–S–R + 2H+
   Polyfunctional Compounds
• Compounds with two or more functional
  groups. Functional groups determine
  chemical properties of compounds

Example:

				
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