aromatic OH

Lecture 4 - Reactions of aromatic compounds and properties and nomenclature of alcohols

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  1. Aromaticiity
    1. Compound shows aromaticity if the ring form of the compound has a higher stability than the open form.
    2. HŸckel Rule
      1. When ring has 4n+2e- in a planer ring the system will exhibit an aromatic quality
      2. Usually the system is a conjugated pi system
  2. Nomenclature of aromatic compounds
  3. Reactions of Aromatic compounds
    1. Halogenation
      1. Commonly need a Lewis acid to polarize or ionize the subsitiuting reagent.
      2. Steps
        1. Substituting group is polarized if ionized to create an electron-deficient species
        2. Cationic intermediate forms by bonding between electron on aromatic ring acting as a nucleophile
        3. hydrogen is lost from carbocation to restore the aromatic ring.
    2. Nitration
    3. Sulfonation
    4. Reaction direction
      1. Observed that aromatic compounds vary in their reactivity when they his different substitution.
      2. Ring activating groups make it easier to add more groups to the ring
      3. Ring deactivating groups make it hards to add more groups to the ring.
      4. Have para,ortho directing and meta directing groups
      5. para,ortho tend to place more charge on the ring. Have bonded electrons directly adjcent to the aromatic ring or electron rich atom
      6. meta directing tend to pull charge away from ring. Usually will have positive charge next to ring.
    5. Mechanism of selectivity
      1. As with other mechanisms selectivity is derived from the stability of the intermediates.
      2. See that with addition to ortho or para position for an ortho, para directing group a resonance structure of peticular stability will be found
      3. For phenol see two intermediates that have 8 e- on all atoms
      4. Not seen for meta product.
      5. Hard to form carbocation intermediate with electron withdrawing group
      6. meta substituent is the least destabilized
      7. See that other forms have adjacent positive charges, very unstable.
  4. Alcohols
    1. Properties and Examples
      1. Overview
        1. alcohols have a n OH on a alkyl chain
        2. OH bond on an aromatic ring gives a phenol
        3. Ether C-O-C
      2. Examples
        1. Methanol (methy alcohol)
          1. Simplest alcohol
          2. Commonly called wood alcohol. Once prepared by heating wood in absence of air
          3. Now usually made from CO
          4. Toxic to humans causing blindness
          5. Highly missiable in water
        2. Ethanol (ethyl alcohol)
          1. One of oldest organic compounds
          2. Product of fermentation of sugar (from grain, grapes)
          3. Beer and wine are 3-5 and 10-13 % respectively
          4. 14% is usually the highest that yeast can exist in
          5. Higher amounts occur through destination
          6. Highest can distill is 95%
          7. Methanol commonly added as a denaturant.
        3. 2-propanol (isopropanol)
          1. Rubbing alcohol
          2. Commonly used disinfectant
          3. Toxic but not as much as methanol
        4. ethylene glycol (1,2-ethanediol)
          1. Common component of antifreeze and as starting material for polyesters
          2. For mammals is a strong central-neverous-system depressant
          3. Sweet taste
          4. Highly solvable in water.
        5. Gylcerol (1,2,3 -propanetriol) Glycerin
          1. Miscible in water.
          2. Not toxic like ethylene glycol, but is sweet
          3. Commonly used in candies, cosmetics, plastics, antifreeze, shock-absorber fluid
          4. Backbone of fats and oils
      3. Properties
        1. Hydrogen bonding dominates charactisites of alcohols
        2. H-bonding
        3. Short chain alcohols like methanol and ethanol are very missiable in water and some organic solvents.
        4. See that have structural properties of both alkanes and water.
        5. Can hydrogen bond with other alcohols and water.
        6. Since can H-bond with itself see an increase in boiling point compared to hydrocarbons on similar MW
        7. As carbon chain increases in length bp increases and water solubility decreases.
        8. Longer carbon chains also more soluble in organic solvents, see that has more hydrocarbon character
    2. Nomenclature
      1. Often referred to by common names that identify alkyl group followed by "alcohol"
      2. IUPAC uses ending "-ol"
      3. Introduces the idea of a priority group
      4. Steps
        1. Name parent compound.
          1. Find longest chain that contains alcohol
          2. alcohol considered a priority group.
          3. As get more functional groups will see that some are named above
          4. Chain name by replacing -e at end of alkane name with "-ol"
        2. Number carbons on main chain
          1. Begin at end closest to hydroxyl group
          2. With more than one alcohol gives the lowest combination of numbers for alcohols
          3. In cyclic alcohol count direction that gives lowest numbers for substituents
        3. Write the name
          1. Number for alcohols is placed right before parent chain, as with alkenes
          2. For multiple -OH use idol, trio etc. Don't delete "-e"
          3. Diols many times called glycols
          4. Add names and numbers of substituents as before
      5. Further designation
        1. As with hydrocarbons can be classified as primary, secondary and tertiary
        2. Classified by the number of C-C that exist on carbon where -OH is attached.
  5. Homework
    1. 13.60, 61, .62, .76, .81
    2. 14.22, .26, .28, .30, .32