Organic Chemistry - PowerPoint 8 by toVV2OW

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									Organic Chemistry


  The Study of the
Compounds of Carbon
Carbon’s Place on the
   Periodic Table
    Unique Properties of Carbon
• Carbon has a modest electronegativity and forms
  primarily covalent bonds
• Carbon is capable of catenation (bonding to itself)
• Carbon has four valence electrons and octet
  requirements require it to bond four times
• Depending on bonding (presence of single, double,
  or triple bonds) carbon compounds can exhibit
  tetrahedral, trigonal planar or linear geometries
• Though carbon and hydrogen form the backbone
  structure, carbon can also bond to other elements,
  like O and N, which are called heteroatoms
            Bond Polarities
• Electronegativity values for some elements
  found in organic compounds are as follows:
  C = 2.5         H = 2.1          O = 3.5
  N = 3.0         F = 4.0          Cl = 3.0
• Obviously C - C bonds are nonpolar
• C - H bonds are essentially nonpolar
• Electronegativity differences between carbon
  and O, N, Cl and F suggest that when carbons
  bonds with one of those elements the bonds will
  be polar
       Carbon Skeletons
Since carbon bonds four times, it can assume
a very complex set of bonding arrangements.

Single bonded carbons can rotate relative to
one another, so arrangements can be
represented in different ways, as shown
below:
                Consider the Diversity of
                 Carbon Compounds
    Single                              Double Bonds              Rings
    Bonds                                                                 C
C       C       C       C       C   C         C       C   C   C
                                                                  C           C
            C                                                         C       C
                                    C     C       C       C   C
                                                                                  C
    C       C       C       C             C
                                                                  C           C

            C                       C     C       C       C       C           C

    C       C       C                      C                      C           C
                                                                      C
            C                       C      C      C       C
                                                                  C           C
                  Hydrogen “Skins”
                                     H                          H
              H
                                   C C C                    C C C
        C C       H
                                                                C
              H                      H
A C atom single-bonded     A C atom single-bonded     A C atom single-bonded
to one other atom gets     to two other atoms gets    to three other atoms gets
three H atoms.             two H atoms.               one H atom.
                                                        H
          C                          H           C     C    C
      C C C
                               C     C
          C                                                         C    C      H
                                      H
A C atom single-bonded     A double-bonded C atom     A double- and single-
to four other atom is      is treated as if it were   bonded C atom or a
already fully bonded (no   bonded to two other        triple-bonded C atom is
H atoms).                  atoms.                     treated as if it were
                                                      bonded to three other
                                                      atoms.
Hydrocarbon Representations
  H H H H H H
H C C C C C C H        Expanded Structure
  H H H H H H


CH3CH2CH2CH2CH2CH3     Condensed Structure


                     Bond-line Representation



      C6H14             Molecular Formula
                       Isomers
Note that for the formula C6H14, several possible structures
exist. These alternate forms are called structural isomers.
Note that each of these isomers is a different compound
with different properties - and a different name.
                                            CH3
  CH3CH2CH2CH2CH2CH3                CH3CH2CHCH2CH3

      CH3                                  CH3
  CH3CHCH2CH2CH3                       CH3CHCHCH3
                                              CH3

 One more isomer exists. Can you suggest what it is?
Hydrocarbon Nomenclature
    PREFIX + ROOT + SUFFIX

                   Number of
    Roots           C atoms

    meth-               1
    eth-                2      Note that
    prop-               3      beginning
    but-                4      with 5 C’s,
    pent-               5      the roots are
    hex-                6
                               numerical
    hept-               7
    oct-                8
    non-                9
    dec-               10
Rules for Naming Alkanes
Note that alkanes contain only single bonds and have the
               generalized formula CnH2n+2
   Rules for Naming Organic Compounds
Alkane Nomenclature Examples
    Suggest appropriate names for the following:

  CH3                              Br
CH3CHCH2CH2CH3                 CH3CHCHCH2CH3

                                        CH3

   CH3    Cl                       CH2CH3     CH3
CH3CHCH2CHCHCH3            CH3CH2CHCHCH2CHCH3
               CH3                      Br
Alkane Nomenclature Examples (II)
         Suggest appropriate names for the following:


       CH3                              Br
    CH3CHCH2CH2CH3                  CH3CHCHCH2CH3

     2-methylpentane                         CH3
                                 2-bromo-3-methylpentane
      CH3    Cl                         CH2CH3     CH3
   CH3CHCH2CHCHCH3              CH3CH2CHCHCH2CHCH3
                  CH3                      Br
3-chloro-2,4-dimethylhexane   4-bromo-5-ethyl-2-methylheptane
      Alkane Nomenclature (III)
  Suggest reasonable structures for the following names:



5-bromo-2,2-dimethyloctane     3-ethyl-2,3,4-trimethylhexane
      Alkane Nomenclature (IV)
  Suggest reasonable structures for the following names:



5-bromo-2,2-dimethyloctane     4-ethyl-2,3,5-trimethylheptane



   CH3       Br                      CH3    CH2H3
CH3CCH2CH2CHCH2CH2CH3           CH3 CH CH CH CH CH2 CH3

   CH3                                   CH3     CH3
Cycloalkane Representations
  cyclopropane          cyclobutane
                               H   H
          H       H
              C              H C   C H

        H C       C H        H C   C H
          H       H            H   H
               Cycloalkanes
Cycloalkanes contain rings, and have the generalized
formula: CnH2n Cycloalkanes are usually represented
by polygons, as shown below:




   Cyclopropane                    Cyclobutane




   Cyclopentane                    Cyclohexane
    Cycloalkane Nomenclature
When only one substituent is on the ring, numbering is not necessary.

        Cl
                            Chlorocyclohexane


When two or more substituents are present, the substituent that is first
alphabetically is assumed to be on carbon one, and the others are
numbered, clockwise or counter-clockwise to give the smallest number
arrangement.

       CH3

                      1-chloro-3-methylcyclohexane

             Cl
             Cl
                    Alkenes
 Alkenes contain at least one double bond.
 Their molecular formula is CnH2n
 The double-bonded carbons have trigonal planar
  geometries.
 An expanded structure for ethene, the simplest alkene,
  is shown below:

           H                   H
               C        C          116.6o
           H                   H
                      121.7o
                   Alkenes (II)
 Note that there is no rotation around a double bond, in
 contrast to single bonds. This factor leads to the
 possibility of cis-trans, or geometric, isomerism. When
 atoms are bonded to double-bonded carbons, they are
 constrained to remain in the same position. For
 example, two kinds of 2-butene exist as is shown below:

CH3                   CH3    CH3                  H
      C        C                     C        C
  H                   H          H                CH3
       cis-2-butene                  trans-2-butene
CH3 groups are cis, or         CH3 groups are trans, or
same side of double bond       opposite one another
     Alkene Nomenclature
• The double bond plays a prominent role
  in alkene nomenclature. Despite
  whatever else is present, the carbon
  chain is numbered from whichever end
  is closest to the double bond.
• When a double bond is present, the
  name ending is changed from -ane to
  -ene.
     Alkene Nomenclature (II)
Example 1:      CH3                    CH2CH3
                         C        C
                    H                  H

This compound is called 2-pentene, or more correctly,
cis-2-pentene, since the continuing carbon chains are
situated on the same side of the double bond.
Generally, if sufficient structure information is provided,
you should assign a cis or trans designation to the name
      Alkene Nomenclature (III)
Other rules we have learned also apply to alkenes, except
that the double bond dictates the direction of chain
numbering. For example:

    CH3CH2                      H     Br
                   C       C
              H                 CH2CHCH3
                  trans-6-bromo-3-heptene


    Note that the double bond determines chain
    numbering, not the bromo group.
    Alkene Nomenclature (IV)
Provide a complete, correct name for the following:


                                      Br
         CH3                    CH2CCH3
                  C        C          CH3
              H                 H
    Alkene Nomenclature (IV)
Provide a complete, correct name for the following:


                                      Br
         CH3                    CH2CCH3
                  C        C          CH3
              H                 H

             cis-5-bromo-5-methyl-2-hexene
                   Cycloalkenes
Cycloalkenes, which have a molecular formula of CnH2n-2,
share many characteristics of alkenes, however, in order to
form rings, the double bond generally must be in the cis form.
When naming a cycloalkene, it is understood that the double-
bonded carbons are numbered 1 and 2. Examples:


                          Cyclohexene



                       3-
                       methylcyclohexene
            CH
            CH33
               Alkynes
• Hydrocarbons containing a triple bond are
  called alkynes, and have molecular
  formulas of CnH2n-2.
• The triple bonded carbons exhibit linear
  geometries, with bond angles of 180o.
• This geometry prevents them from
  forming rings.
• Nomenclature for alkynes is completely
  analogous to the method for alkenes.
      Aromatic Hydrocarbons
• Aromatic hydrocarbons are ring structures
  with multiple double bonds. The double
  bonds are conjugated, alternating double
  and single bonds.
• Aromatic hydrocarbons have molecular
  formulas approaching CnHn.
• These structures are planar, with all ring
  carbons exhibiting a trigonal planar
  geometry, and a high degree of resonance.
• A number of aromatics are notorious
  carcinogens
        Aromatic Nomenclature


   OH        NH2
             NH2       CH
                       CH33     OH
                                OH       COOH
                                         OH




Benzene   Aniline   Toluene   Phenol   Benzoic
                                        Acid
     Aromatic Nomenclature (II)
Nomenclature for aromatics is performed much like other
cyclic compounds.
If only one substituent is present, numbering is unnecessary
If one of the common names, such as phenol, is used, it is
understood that the substituent is on carbon 1. Other
substituents present are numbered or given a special
designation used in aromatic chemistry.
In general, substituents are numbered by counting
clockwise or counterclockwise to produce the lowest
numbering pattern.
    Aromatic Nomenclature (II)
• Nomenclature for aromatics is performed much like
  other cyclic compounds.
• If only one substituent is present, numbering is
  unnecessary
• If one of the common names, such as phenol, is used, it
  is understood that the substituent is on carbon 1. Other
  substituents present are either numbered or given a
  special designation used in aromatic chemistry.
• 1-2 substitution is called ortho
• 1-3 substitution is called meta
• 1-4 substitution is called para
    Aromatic Nomenclature (III)
Examples:

                            CH
                            CH33               OH
                                               OH
      NH2
                                                      CH
                                                      CH33


            Cl
                            Br
                            Cl                 CH
                                               CH33
 3-chloroaniline       4-bromotoluene
                                         2,4-dimethylphenol
        or                   or
meta-chloroaniline   para-bromotoluene
    Hydrocarbon Chemistry
• Hydrocarbons are generally derived
  from natural sources, particularly
  petroleum.
• The most plentiful compounds in
  petroleum are alkanes.
• A number of reactions can be used to
  convert one type of hydrocarbon into
  another.
• Organic compounds are much more
  reactive when heteroatoms, N and O,
  are present.
               Alkanes
• Alkanes are generally considered to be
  unreactive.
• They are commonly combusted as
  gasoline, diesel, kerosene, etc.
• They can also be reacted with the
  halogens, e.g. Cl2 and Br2, to form
  halogenated forms.
• The halogenated forms can be used to
  produce other compounds.
                    Alkenes
• The double bond in alkenes makes them much
  more reactive than alkanes.
• The pi electrons in the double bond are relatively
  loosely held, and the double bond is subject to
  attack by substances attracted to negative charge
  (electrophiles).
• Generally, substances are added to the doubly
  bonded carbons, and the double bond is lost.
• Ethylene and propylene are heavily used to
  produce polymers polyethylene and
  polypropylene.
                 Alkynes
• Alkynes have two pi bonds, and react
  much like alkenes, except that
  stoichiometrically they tend to react twice
  as much.
• The most common alkyne, acetylene, is
  capable of participating in unusual
  reactions with strong bases, and it
  combusts at very high temperature, which
  makes it ideal for welding torches.
       Aromatic Compounds
• Although aromatic compounds contain
  double bonds, they do not react like
  alkenes, because the loss of double bonds
  would eliminate their stabilizing resonance.
• Instead, aromatic compounds tend to
  undergo substitution reactions, where other
  substances replace hydrogen atoms on the
  ring carbons.
• A number of aromatic hydrocarbons are
  produced as pollutants when other
  hydrocarbons are burned.
          Functional Groups
• When organic compounds contain elements
  other than carbon, called heteroatoms, such
  as oxygen and nitrogen, the structural units
  containing the heteroatoms are called
  functional groups.
• These functional groups add unique
  chemical characteristics to the compound,
  which makes them very important in
  biological applications.
                  Alcohols
• When a carbon atom is bonded to an -O-H
  group, often designated as R-O-H, where R
  is used as a general designation for a carbon
  group, the molecule is called an alcohol.
• The -OH group is very polar, and most small
  alcohols have high boiling points and good
  water solubility.
• Besides simple alcohols, alcohols are found
  biologically in carbohydrates and various
  metabolites.
         Alcohol Nomenclature
• Alcohols often have common trivial names,
  but IUPAC nomenclature rules suggest that
  the alcohol name contain the -ol suffix.
• The alcohol group is considered higher
  priority than any carbon-containing group,
  and the chain should be numbered from
  whichever end is closest to the alcohol
  group.
• Other groups are named and numbered as
  shown previously
       Alcohol Nomenclature (II)
Examples:
                    Ethyl alcohol (trivial name)
CH3CH2-OH
                    Ethanol (IUPAC name)
  Cl     OH
                    4-chloro-2-pentanol
CH3CHCH2CHCH3

Br    CH3 OH
                    6-bromo-4-methyl-2-hexanol
CH2CH2CHCH2CHCH3

 OH
                    3-methylcyclohexanol

       CH3
                    Ethers
• Another oxygen-containing functional group
  is the ether. The ether group, sometimes
  designated as R1-O-R2, contains an oxygen
  bridge between two carbon atoms.
• Ethers, unlike alcohols, do not participate in
  hydrogen bonds, and are not considered
  polar.
• Ethers, which are important medical and
  industrial chemicals, are not commonly
  found naturally in biological systems.
        Ether Nomenclature

• Although IUPAC recommends a method
  for naming ethers, we will only focus on
  a trivial method that is in common use.
• With this method, the two carbon-
  containing groups connected by the
  oxygen are listed alphabetically,
  followed by the name “ether”.
       Ether Nomenclature (II)
Examples:


CH3-O-CH2CH3                    Ethyl methyl ether
       O
            CH3                 Cyclohexyl methyl ether


CH3CH2-O-CH2CH3                 Diethyl ether


Diethyl ether was used for years as an anesthetic until it
was replaced due to safety considerations.
             Carbonyl Groups
• The carbonyl group contains a carbon-
  oxygen double bond. This functional group
  can be found in the interior of a carbon
  chain, where it is called a ketone, or on a
  terminal carbon, where it called an aldehyde.
• A commonly used representations of
  ketones and aldehydes look as follows:
      O                   O
      ||                  ||
   R1-C-R2              R-C-H       or     RCHO

    Ketone                      Aldehyde
         Carbonyl Groups (II)
• Carbonyl groups, particularly aldehydes, are very
  reactive, and appear in many biological
  compounds.
• Like alcohols, carbonyl groups are found in
  carbohydrates, and they are observed during
  many metabolic processes
• These compounds are moderately polar, and the
  smaller ketones and aldehydes are water soluble.
• A number of ketones have common names, such
  as acetone and methyl ethyl ketone (MEK), and
  are widely used industrial solvents.
        Ketone Nomenclature
• When a ketone is present in a compound, it
  is considered higher priority than anything
  discussed thus far, and the chain is
  numbered from whichever end is closest to
  the ketone. If an alcohol is also present, it
  is given a number and is called a hydroxy
  group.
• When a ketone is present, the suffix for the
  name is changed to -one.
     Ketone Nomenclature (II)
Examples:
    O            Acetone (trivial name)
    ||
 CH3CCH3         2-propanone (IUPAC name)

    O            Methyl ethyl ketone (trivial name)
    ||
 CH3CCH2CH3      2-butanone (IUPAC name)


     O   OH
     ||  |
CH3CHCCH2CHCH3   5-hydroxy-2-methyl-3-hexanone
   |
   CH3
        Aldehyde Nomenclature
• When an aldehyde is present in a compound, it is
  considered higher priority than anything discussed
  thus far, and the chain is numbered from aldehyde
  end. The aldhyde group is understood to be on the
  terminal carbon, so it needs no number. If ketones
  are also present, they are called “oxo” groups and
  are given a number.
• When an aldehyde is present, the suffix of the name
  is changed to -al.
• Remember, aldehydes can be represented as:
                O
                ||
              R-C-H      or   RCHO
    Aldehyde Nomenclature (II)
Examples:
    O            Formaldehyde (trivial name)
    ||
 CH3C-H          Methanal (IUPAC name)


    O
    ||
 CH3CCH2CHO      3-oxobutanal



      O  OH
      || |
CH3CHCCH2CHCHO   5-chloro-2-hydroxy-4-oxohexanal
   |
   Cl
              Carboxylic Acids
• Carboxylic acids have the generalized formula:
                   O
                   ||
                 R-C-OH   or RCOOH

• The “carboxyl” name is a contraction of carbonyl
  and hydroxyl group names, which are both
  present.
• The hydrogen on the hydroxyl group is acidic, and
  carboxylic acids are notable for their acidic
  behavior.
• Carboxylic acids are found in many biological
  compounds, most notably amino acids.
   Carboxylic Acid Nomenclature
• The carboxylic acid structure requires that this
  functional group be on a terminal carbon.
• The carboxyl group has higher priority than
  any other functional group, and if it is present,
  it is understood to be on carbon number 1,
  and the chain is numbered away from it.
• Other groups present are numbered
  appropriately, and the name’s suffix is
  changed to -oic, followed by the word “acid”.
• There are many trivial names, such as acetic
  acid that are commonly used.
Carboxylic Acid Nomenclature (II)
Examples:
   O              Acetic acid (trivial name)
   ||
CH3C-OH           Ethanoic acid (IUPAC name)


OH                Gamma-hydroxybutyric acid or GHB
|                        (trivial name)
CH2CH2CH2COOH
                  4-hydroxybutanoic acid

      Cl CH3
      |  |
CH3CHCCH2CHCOOH   4,5-dichloro-2-methylhexanoic acid
   |
   Cl
                 Amines
• Amines act as bases in organic chemistry.
• They contain the amino functional group:
                  R-NH2
• These compounds are notable for their
  basic nature and strong odors.
• Nitrogen-containing compounds, or amines,
  are found in a variety of biological
  compounds including amino acids and
  nucleic acids.
            Amine Nomenclature
• Amines are commonly named by referring to the alkyl
  group attached to them, followed by the word “amine”.
• In IUPAC, or systematic, nomenclature, the amine is
  numbered from which ever end of the chain is closest.
• The final “e” of the name is replaced by the suffix -amine.
• If a higher priority group is present, the amine is called an
  “amino” group and given a number. All of the oxygen-
  containing functional groups are considered higher priority.
• Finally, though we won’t cover them, amines exist where
  more than one carbon group is attached to the nitrogen
  atom.
      Amine Nomenclature (II)
Examples:
   NH2           Isopropyl amine (trivial name)
   |
CH3CHCH3         2-propanamine (IUPAC name)

   NH2
   |
CH3CHCH2CH2-OH   3-amino-1-butanol


    NH2           Alanine (amino acid)
    |
 CH3CHCOOH        2-aminopropanoic acid

								
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