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Grade_12u_organic_hydrocarbons_alkanes

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					Unit: Organic
  Chemistry

        Alkanes
Classifying Hydrocarbons
                             Hydrocarbons
                       (compounds with C, H – and
                         possibly O, N, halogens)



          Aliphatics           Aromatics      Derivatives
                                              (e.g.,
                                              alcohols,esters)
                                              etc
Alkanes    Alkenes      Alkynes
Non polar
 tetrahedral in
shape
 Has 4 bonds and
4 atoms for each C
Hydrocarbons


   Saturated Hydrocarbon –
    compounds that contain only
    single bond

   Unsaturated
    Hydrocarbons – a
    hydrocarbon that contains
    carbon-carbon double or
    triple bond
Alkane in the shape of a ring (cyclo-alkanes) have
the formula CnH2n

        H                 H       H
H       H       H     H H           H
                                  H
H H         H H       H H         H H

    H       H           H         H
Alkanes
   Physical Properties
       Non-polar molecules
                                        Rotation around single bond
       Not soluble in water
       Low density
       Low melting point      These go up as the number of
                               carbons increase
       Low boiling point
Comparing the Sizes and Boiling
Points of Alkanes
Size (# of atoms per   Boiling Point Range     Examples of Products
     molecule)                 (oC)
       1 to 5               Below 30           Gases: used for fuels to
                                                cook and heat homes

      5 to 16               30 to 275             Liquids: used for
                                              automotives, diesel, etc.

      16 to 22              Over 250          Heavy liquids: used for oil
                                             furnaces and lubricating oils
      Over 18               Over 400             Semi-solids: used for
                                               lubricating greases and
                                              waxes to make candles,
                                             waxed paper and cosmetics
      Over 26               Over 500           Solid residues: used for
                                                  asphalts and tars
Naming Straight-Chain Alkanes
      Name     Number of C atoms   Molecular Formula
     Methane          1                  CH4
     Ethane           2                  C 2H 6
     Propane          3                  C 3H 8
     Butane           4                 C4H10
     Pentane          5                 C5H12
     Hexane           6                 C6H14
     Heptane          7                 C7H16
     Octane           8                 C8H18
     Nonane           9                 C9H20
     Decane           10                C10H22
       Representing Structures
• Molecular Formula – shows ratios of atoms
                 C3H8

• Complete Structural Diagram – shows arrangement of
  atoms

• Line diagram – using lines to represent molecular
  structure

• Condensed Structural Diagram keeps it on one line.
     CH3 – CH2 – CH3

• Isomers have the same molecular formula but a different
  structural formula.
              C40H82 has ???? isomers
Isomerism in Alkanes
Carbon   Number of possible isomers
Number
1        1
2        1
3        1
4        2
5        3
6        5
7        9
8        18
9        35
10       75
15       4,347
20       366,319
30       4,111,846,763
40       62,491,178,805,831
Expanded Molecular Formulas
   Show groupings of atoms in a large
    molecule
             Name         Expanded Molecular
                               Formula
            Methane              CH4
             Ethane            CH3CH3
            Propane          CH3CH2CH3
             Butane         CH3(CH2)2CH3
            Pentane         CH3(CH2)3CH3
            Hexane          CH3(CH2)4CH3
            Heptane         CH3(CH2)5CH3
             Octane         CH3(CH2)6CH3
            Nonane          CH3(CH2)7CH3
            Decane          CH3(CH2)8CH3
Naming Alkanes
1)   Find the longest carbon chain. Use as base
     name with an ane ending.
2)   Number the chain from end which will give
     the lower set of substituent numbers. (alkyl
     or halogens)
3)   Name and number each substituent. Use
     base names with a yl ending.
4)   For multiple branch of the same type, modify
     name with di, tri,….
5)   List multiple branches alphabetically the di,
     tri … don’t count
  Other branches
•When other atoms are branches use
the following names
• Cl - chloro
• Br – bromo
• I – iodo
• F – Fluro
• NO2 - Nitro
• NH2 – amino
• OH - Hydroxy
Organic Nomenclature
Example - build




           3D Arrangement
Rules for Drawing Alkanes
1.   In a straight line, draw the carbon atoms in
     the parent chain. The number of carbon
     atoms is indicated by the root of the name.
2.   Give positions numbers to the carbon
     atoms in the parent chain carbon atoms.
3.   Add any groups to the assigned positions.
4.   Add enough hydrogen atoms and bonds for
     each carbon atom to have four bonds.
An Example
   2-ethyl-3,4-dimethylhexane


                    CH2CH3

              CH3   CH CH CH CH2 CH3
              1     2   3    4    5   6

                        CH3 CH3
                   Examples
                                            H
                                      H          H
                        cyclobutane   H H       H H

cyclopropane        H        H           H    H
                                      cyclopentane
               H                 H
                    H        H
               H                 H
                    H       H
                   cyclohexane
        Substituted cycloalkanes

                                                                  CH3
    H3C        CH3                    CH3

                           H     H    CH3
                           H H       H H
1,1-dimethylcyclopropane       H    H
                     1-ethyl-2-methylcyclopentane          H3C
                                                1-ethyl-2-methylcyclobutane
Naming Alkanes worksheet

Worksheet 1
http://www.arps.org/users/HS/thompsom/che
mcom/unit_3/Naming_Alkanes_Worksheet_1
.pdf

Worksheet 2
http://www.arps.org/users/HS/thompsom/che
mcom/unit_3/Naming_Alkanes_Worksheet_2
.pdf

				
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posted:11/19/2012
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