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Organic Chemistry II CHEM 271

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Organic Chemistry II CHEM 271 Powered By Docstoc
					Organic Chemistry II

    CHEM 271
      Chapter One
Alcohols, Diols and Thiols
Nomenclature of Alcohols
 Functional Class Nomenclature
  of Alcohols( Common Names)
Name the alkyl group and add "alcohol" as a
separate word.
                                 CH3
    CH3CH2OH
   Ethyl alcohol               CH3CCH2CH2CH3

                                 OH
CH3CHCH2CH2CH2CH3

  OH                          1,1-Dimethylbutyl
                                   alcohol
1-Methylpentyl alcohol

                4
    IUPAC Nomenclature of Alcohols
•Name as "alkanols." Replace –e ending of alkane
name by -ol.
•Number chain in direction that gives lowest number
to the carbon that bears the —OH group.
   CH3CH2OH                    CH3
    Ethanol
                            CH3CCH2CH2CH3
CH3CHCH2CH2CH2CH3              OH

   OH                      2-Methyl-2-pentanol

  2-Hexanol
                      Name these:

      CH3
                                         OH
CH3   CH CH2OH
                              CH3        CH CH2CH3
2-methyl-1-propanol
                                    2-butanol

            CH3                                     OH
      CH3   C OH
            CH3
                                    Br        CH3
   2-methyl-2-propanol
                          3-bromo-3-methylcyclohexanol
                                                  =>
                                                         6
         Unsaturated Alcohols

 Number the chain in thedirection that gives the
  lowest number to the carbon that bears the OH
  group

                 OH
   CH2   CHCH2CHCH3          4-penten-2-ol (old)

     pent-4-ene-2-ol
                       =>



                                                    7
                Naming Priority
•   Acids                   •     Alkenes
•   Esters                  •     Alkynes
•   Aldehydes               •     Alkanes
•   Ketones                 •     Ethers
•   Alcohols                •     Halides
•   Amines

                                            =>


                     Chapter 10                  8
          Hydroxy Substituent

• When -OH is part of a higher priority class of
  compound, it is named as hydroxy.
• Example:

   OH
   CH2CH2CH2COOH

  4-hydroxybutanoic acid                           =>



                                                        9
• Primary: carbon with –OH is bonded to one
  other carbon.    -CH2OH

• Secondary: carbon with –OH is bonded to two
  other carbons.   -CHOH

• Tertiary: carbon with –OH is bonded to three
  other carbons.        -COH
                                   =>


                                                 10
      CH3                       CH3
                         CH3    C    OH
CH3   CH CH2OH
                                CH3


                  OH
            CH3   CH   CH2CH3       =>
                                          12
                     Diols

• Two numbers are needed to locate the two
  -OH groups.
• Use -diol as suffix instead of -ol.


      HO                           OH

            1,6-hexanediol

                                             =>
                      Chapter 10                  13
                    Glycols
• 1, 2 diols (vicinal diols) are called glycols.
• Common names for glycols use the name of the
  alkene from which they were made.

      CH2CH2                 CH2CH2CH3
     OH OH                   OH OH
  1,2-ethanediol           1,2-propanediol

  ethylene glycol          propylene glycol
                                              =>
                                                   14
              Glycrol
• 1, 2,3 Triols are called glycrol>

          C H2 CHCH2


          OH OHOH
                         Thiols

• Contains an –SH (sulfhydryl) group.

• Is named by selecting the longest carbon chain that
  contain the -SH. We add -thiol to the name of the parent
  alkane.

• Parent chain is numbered from the end nearest tothe -SH
  group.
    Methanethiol          Ethanethiol
       CH3─S─H            CH3─CH2─S─H
    Physical Properties of Alcohols

1. Alcohols are polar molecules (because of O-H and C-
   O).
2. Have higher boiling point than Alkanes, Alkenes &
   Alkynes due to Hydrogen bonding involves oxygen of
   one molecule and hydrogen of another in alcohol
   molecules.
3. As the molecular weight increase, boiling point
   decrease.
4. As the molecular weight increase, solubility in water
   decrease .
5. The solubility of alcohols in water is due to hydrogen
   bonding between alcohol and water molecules.
6. They are weak acids (weaker than Phenol).
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:
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:
          Acidity of Alcohols
pKa range: 15.5-18.0 (water: 15.7)
Acidity decreases as alkyl group
 increases.
Halogens increase the acidity.
Phenol is 100 million times more acidic
 than cyclohexanol!
                                 =>

                   Chapter 10              21
Preparation of Alcohols by Hydration of
                Alkenes
Water molecule add to double bond in accordance with
Markovnikov’s rule
      Preparation of Alcohols by Grignard
                         Reagents
By reaction of grignard reagents with aldehydes and
ketones to form Primary, Secondary and Tertialy
Alcohols.
                      H
                                  Ether
CH 3CH2MgBr    +          C   O           CH 3CH2CH2OH
                                  H3O +
                      H                   primary alcohol


                   H3 C                          CH 3

                                  Ether
CH 3CH 2MgBr   +          C   O           CH 3CH 2CHOH
                                  H3O +
                     H                    Secondry alcohol

                   H3 C                          CH 3

                                  Ether
CH 3CH 2MgBr   +          C   O           CH 3CH 2COH
                                  H3O +
                   H3 C                          CH 3

                                          Tertiary alcohol
Preparation of Alcohols by Reduction of
        Aldehydes and Ketone
Preparation of Alcohols by reduction of
     Carboxylic acids and Esters
Preparation of Alcohols from
         Epoxides
        Preparation of Diols
Diols formed by reduction of dialdehyde by
catalytic hydrogenation as the following
reaction.
Mechanism of Reaction
        Preparation of Thiols

By the reaction of alkyl halide with
thiourea to give thiol compound
      Reactions of Alcohols

1- Reaction with Hydrogen Halide
2- Reaction with Thionyl Chloride
3- Acid Catalyzed Dehydration
 4- Conversion of Alcohols to Ethers
By Heating primary alcohols in the presence of
Sulfuric acid (Condensation reaction)
5- Esterification
6- Oxidation of Alcohols
Primary alcohol is oxidized under strong or mild
oxidizing agents to give acid or aldehyde




PCC : Pyridinium Chlorochromate
      Reaction of Diols
Oxidative Cleavage of Vicinal Diols
         Reactions of Thiols
Thiols are weak acids but more acidic
than alcohols.
2- Oxidation of Thiols

				
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