Chapter 10--Alkanes by G2iv1V

VIEWS: 10 PAGES: 47

									CHAPTER 10--ALKANES
Dr. Ellen Wilson, RPh, PhD
CHE1230
WHY ARE THERE SO MANY
  ORGANIC COMPOUNDS?
                                           Carbon




WHY ARE THERE SO MANY CARBON COMPOUNDS?
                                            forms
                                           stable,
                                          covalent
                                           bonds
                                             with
                                            other
                                           carbon
                                           atoms

                                           What
                                          does this
                                           mean?
                                TYPES OF BONDING
  Covalent Bonding                  Ionic Bonding

  Sharing of electrons            Transfer of electrons
   CH3CH2CH2CH2CH3                   Na+ + Cl- = NaCl
Organic chemistry bonding       Inorganic chemistry bonding
  Partial charges & dipole           Full charges, ions
          moments                    Lattice structures
    Discrete molecules              Dissociate in water
Dissolve but don’t dissociate           Electrolytes
      Nonelectrolytes
               WHY ARE THERE SO MANY
                 ORGANIC COMPOUNDS?
Carbon forms stable, covalent bonds with other
   atoms such as H, O, N, S, and halogens
           WHAT IS A FUNCTIONAL GROUP?



 A specific group of atoms within a molecule that
                        help
define the properties and reactivity of the molecule

 Will have the same properties regardless of the
        molecule to which it is attached
COMMON FUNCTIONAL GROUPS




See inside back cover of text for these examples and more….
FUNCTIONAL GROUPS MAKE A BIG
DIFFERENCE




                  Butane      Pentane   Butanol
                    Gas        Liquid    Liquid
                  BP=-0.5oC    36.1oC   117.73oC
                   Insoluble in water   Soluble
FUNCTIONAL GROUPS GIVE UNIQUE PROPERTIES
   Many biologically active molecules are esters,
    ethers, carboxylic acids, and amines
FUNCTIONAL GROUPS ALLOW US TO
PREDICT PROPERTIES OF MOLECULES

 All alcohols will have the same general properties
 All amines will have the same general properties

 All carboxylic acids will have the same general
  properties

   Even within a larger molecule, the functional
    group will have predictable properties even if
    they are not the properties of the entire molecule
            WHY ARE THERE SO MANY
              ORGANIC COMPOUNDS?
Carbon can form double and triple bonds
with other carbon atoms or other atoms
                WHY ARE THERE SO MANY
                  ORGANIC COMPOUNDS?
The number of ways that carbon and other atoms
       can combine is almost limitless
TWO COMPOUNDS CAN HAVE EXACTLY
THE SAME MOLECULAR FORMULAS BUT
              HAVE
DIFFERENT PROPERTIES BASED ON THE
   ARRANGEMENT OF THE ATOMS
Each of the statements given below is true but
John Dalton may have had trouble explaining them
with his atomic theory. Give explanations for each
of the following statements:

     ethyl alcohol and dimethyl ether have the same
      composition by mass—52% carbon, 13% hydrogen,
      and 35% oxygen. However, they have different
      melting points, boiling points, and solubility in
      water.
COMPOUNDS THAT HAVE THE SAME
   MOLECULAR FORMULA BUT
DIFFERENT STRUCTURAL FORMULAS
ARE CALLED STRUCTURAL ISOMERS
IN LAB, YOU HAVE ALREADY DISCOVERED SOME
OF THE PROPERTIES OF HYDROCARBONS



WHAT MAKES THE PHYSICAL PROPERTIES OF
HYDROCARBONS DIFFERENT FROM THE
PHYSICAL PROPERTIES OF INORGANIC
COMPOUNDS?
    BONDING MAKES THE DIFFERENCE
  Covalent Bonding                  Ionic Bonding

  Sharing of electrons            Transfer of electrons
   CH3CH2CH2CH2CH3                   Na+ + Cl- = NaCl
Organic chemistry bonding       Inorganic chemistry bonding
  Partial charges & dipole           Full charges, ions
          moments                    Lattice structures
    Discrete molecules              Dissociate in water
Dissolve but don’t dissociate           Electrolytes
      Nonelectrolytes
      HOW DO MELTING/BOILING POINTS
                DIFFER?
    Organic Compounds       Inorganic Compounds

   Low MP and BP          High MP and BP
       HOW DOES SOLUBILITY DIFFER?
    Organic Compounds       Inorganic Compounds

 Often insoluble in     Soluble in water
  water                  Why?
 Why?

 Why not?
      HOW DO REACTION RATES DIFFER?
    Organic Compounds         Inorganic Compounds

   Often slow to react      Much easier to react
                   COMPARISON
       METHANE                    NaCl

 Type of bonding?        Type of bonding?
 BP = -164oC             BP = 1433oC

 MP = -182oC             MP = 801oC

 Slightly soluble in     36g/100mL water
  water                   Nonflammable
 Flammable               Quick to react
 Slow to react           Exists at S at RT
 Can be S, L or G        Electrolyte
 Nonelectrolyte
          OVERVIEW OF HYDROCARBONS


                       Hydrocarbons




                aliphatic         aromatic




  Alkanes
                alkenes           alkynes
&cycloalkanes
WHAT ARE ALKANES?
 Saturated
 Base molecule contains only C and H

 No double or triple bonds
THE FIRST FOUR ALKANES
 Methane,    ethane, propane, butane


 CH4,   C2H6, C3H8, C4H10
  A MOLECULAR FORMULA
     CH4, C2H6, C3H8, C4H10

GIVES THE TYPE AND NUMBER OF
 ATOMS IN THE COMPOUND BUT
  TELLS NOTHING ABOUT THE
STRUCTURE OF THE COMPOUND
A STRUCTURAL FORMULA
GIVES THE ACTUAL ARRANGEMENT
OF THE ATOMS IN A MOLECULE


           H H H H
       H             H
           H H H H
A CONDENSED FORMULA
REPRESENTS THE ARRANGEMENT
OF THE ATOMS WITHOUT DRAWING
ALL THE BONDS

             CH4
            CH3CH3
          CH3CH2CH3
         CH3CH2CH2CH3
STRUCTURAL AND CONDENSED FORMULAS
ARE ESPECIALLY USEFUL WHEN
DEALING WITH STRUCTURAL ISOMERS

       butane                isobutane

       C4H10                  C4H10

  CH3CH2CH2CH3               (CH3)3CH

                                   H
       H H H H                 H       H

   H             H       H                 H
                     H                         H
       H H H H           H         H       H
REMEMBER, REMEMBER, REMEMBER……

            CARBON FORMS 4 BONDS

          HYDROGEN FORMS 1 BOND
STRUCTURAL AND CONDENSED FORMULAS
ARE ESPECIALLY USEFUL WHEN
DEALING WITH ISOMERS

      pentane               isopentane

      C5H12                     C5H12

CH3CH2CH2CH2CH3     CH3CH(CH3)CH2CH3
                                H
    H H H H H               H       H

H               H       H               H   H
                    H                           H
    H H H H H           H       H       H   H
PRACTICE:
   Write the structural formulas from the
    following condensed formulas:

       CH3CH2C(CH3)3

       (CH3)3CC(CH3)3

       (CH3)3CBr
PRACTICE:
                           H           H       H        H
                       H                                    H
                           H           H                H
                                                        H
                                           H                H
                                                        H


Write the                                  H
                                               H
                                                    H
                                                                            H        H
                                                                        H       HH       H
condensed formulas                                              H                            H
                                                            H                                    H
from the following                                              H                    H
                                                                                     H
                                                                                             H


structural formulas:
                                                                        H                H
                                                                                     H
                                                                        H       H
                                                                            H
                                               H
                                           H        H

                                   H                    H           H
                               H                                        H
                                   H                    H           H

                                               Br
NOMENCLATURE OF ALKANES
   NAME the parent compound
       The first TEN straight chain alkanes are:
                               Methane
                                Ethane
                               Propane
                                Butane
                               Pentane
                               Hexane
                               Heptane
                                Octane
                               Nonane
                                Decane
NOMENCLATURE OF ALAKNES
   NUMBER the parent compound

       Find the longest chain

       Start numbering so that any substituents get the
        lowest number possible
REPRESENTATIVE SUBSTITUENTS
                --CH3
              --CH2CH3
            --CH2CH2CH3
          --CH2CH2CH2CH3
        --CH2CH2CH2CH2CH3

                --F
               --Br
               --Cl
                --I
EXAMPLES:
   Name & number the longest continuous carbon
    chain

   Name and number the substituent


                      H   H      H
                  H                   H
                      H          H

                          Br
EXAMPLES:
   Name & number the longest continuous carbon
    chain

   Name and number the substituent


                               Cl
                  H     H             H
              H                           H
                  H     H      H      H
EXAMPLES:
   Name & number the longest continuous carbon
    chain

   Name and number the substituent


                    I
                H       H    H    H     H
            H                               H
                H   H   H    H          H

                                  I
MORE EXAMPLES:
   Name & number the longest continuous carbon
    chain

   Name and number the substituent


                       H               H               H
                   H       H       H       H       H       H
           H   H               H               H               H   H   H
       H                                                                   H
           H   H       H       H       H       H       H       H   H   H
MORE EXAMPLES:
   Name & number the longest continuous carbon
    chain

   Name and number the substituent


                                      H
                                  H       H
                 H   H       H                H
             H                                    H
                 H   H                        H
                         H       HH       H
                             H        H
REACTIONS OF ALKANES
   Combustion
       An alkane + oxygen
        gives carbon dioxide
        plus water

       An important side
        reaction?
REACTIONS OF ALKANES
   Halogenation—an alkane plus a halogen gives
    an alkyl halide (substituted alkane) plus a
    hydrogen halide (acid)



             CH4 + Br2 → CH3-Br + HBr

         CH3CH3 + Cl2 → CH3CH2-Cl + HCl
IS YOUR CYCLOALKANE A
BOAT OR A CHAIR?
IS YOUR HYDROGEN AXIAL OR
EQUATORIAL?

								
To top