1. Alkanes and Aromatic Hydrocarbons
Organic Compounds
Bonding in Hydrocarbons
Naming Alkanes
Properties of Alkanes
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2. Timberlake LecturePLUS
“The most important hypothesis in all of
biology…is that everything that animals do,
atoms do. In other words, there is nothing
that living things do that cannot be
understood from the point of view that
they are made of atoms acting according
to the laws of physics.”
Richard Feynman ( )
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Organic Compounds
Contain carbon
Have covalent bonds
Have low melting points
Have low boiling points
Burn in air (oxygen)
Are soluble in nonpolar solvents
Form large molecules
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Alkanes
Contain C and H only
Contain single bonds C-C
Have 4 bonds to every carbon (C) atom
Are nonpolar
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5. Complete Structural Formulas
Show the bonds between each of the atoms
H H
 
H  C  H H C H
CH4 , methane
In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.
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More Alkanes
H H Condensed Structural Formulas
H C C H CH3 CH3
H H Ethane
H H H
H C C C H CH3 CH2 CH3
H H H Propane
The complete structural formula for ethane shows the single bonds between two carbon atoms and six H atoms. The complete structural formula of propane shows the 3-carbon chain with single bonds to the attached H atoms. To write a condensed structural formula, the H atoms are written as a group next to their respective C atoms.
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IUPAC Names
Name # carbons Structural Formula
Methane 1 CH4
Ethane 2 CH3CH3
Propane 3 CH3CH2CH3
Butane 4 CH3CH2CH2CH3
Pentane 5 CH3CH2CH2CH2CH3
The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family.
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IUPAC NAMES
Name # carbons Structural Formula
Hexane CH3CH2CH2CH2CH2CH3
Heptane CH3CH2CH2CH2CH2CH2CH3
Octane CH3CH2CH2CH2CH2CH2CH2CH3
Nonane CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
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Learning Check Alk1
A. What is the condensed formula for
H H H H
H C C C C H
B. What is its molecular formula?
C. What is its name?
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Solution Alk1
A. CH3CH2CH2CH3
B. C4H10
C. butane
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Reactions of Alkanes
Combustion
alkane + O CO2 + H2O + heat
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Combustion In the Cell
Metabolic oxidation is combustion
C6H12 O6 + 6O CO2 + 6H2O + heat
glucose
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Learning Check Alk2
Complete the combustion reaction for
C3H8 + O
Balance your equation
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Solution Alk2
Step 1
C3H8 + O CO2 + H2O
Step 2
C3H8 + O CO2 + 4 H2O
Step 3
C3H8 + 5 O CO H2O
To balance the atoms in the formula C3H8, we place a coefficient of 3 in front of CO2 and a coefficient of 4 in front of H2O. The total O in the products is 10 O (6 O in 3CO2 and 4 O in 4 H2O). To balance the 10 O, a coefficient of 5 is placed in front of the O2.
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Learning Check Alk3
Complete and balance the reaction for the complete combustion of C7H16
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Solution Alk3
Step 1
C7H16 + O CO2 + H2O
Step 2
C7H16 + O CO2 + 8 H2O
Step 3
C7H O CO2 + 8 H2O
The carbon has a subscript 7, which means we need to place a coefficient of 7 in front of CO2. The H subscript 16 is balanced by placing a coefficient of 8 in front of H2O. Finally, the total O of 22 ( ) indicates that a coefficient of 11 in front of O2 will balance the O atoms.
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