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Organic Chemistry. Alkanes. Alkanes. Contain C and H only Contain single bonds C-C Have 4 bonds to every carbon (C) atom Are nonpolar. Complete Structural Formulas. Show the bonds between each of the atoms H H H C HH C H - PowerPoint PPT Presentation
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Alkanes
Organic Chemistry
Timberlake LecturePLUS 2
Alkanes
Contain C and H only
Contain single bonds C-C
Have 4 bonds to every carbon (C) atom
Are nonpolar
Timberlake LecturePLUS 3
Complete Structural Formulas
Show the bonds between each of the atoms
H H
H C H H C H H H
CH4 , methane
Timberlake LecturePLUS 4
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
Timberlake LecturePLUS 5
IUPAC Names
Name # carbons Structural Formula
Methane 1 CH4
Ethane 2 CH3CH3
Propane 3 CH3CH2CH3
Butane 4 CH3CH2CH2CH3
Pentane 5 CH3CH2CH2CH2CH3
Timberlake LecturePLUS 6
IUPAC NAMES
Name # carbons Structural Formula
Hexane 6 CH3CH2CH2CH2CH2CH3
Heptane 7 CH3CH2CH2CH2CH2CH2CH3
Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3
Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
AlkanesAlkanes are a family of hydrocarbons containing only single bonds between
the carbon atoms
Methane
Tetrahedral
Expanded structural formula: showing each bond line.
CH4Molecular formula
Ethane
C2H6 Molecular formula
Expanded structural formula
CH3 – CH3
Condensed structural formula: with each carbon atom and
its attached hydrogen atoms.
Alkanes
Homologous Series general formulaCnH2n+2
n: number of carbon atoms
Naming of Alkanes
CnH2n+2Prefix + ane
No of C atoms Prefix1 meth-2 eth-3 prop-4 but-5 pent-6 hex-7 hept-8 oct-9 non-
10 dec-
• Carbon-to-carbon chains can be (A) straight, (B) branched, or (C) in a closed ring.
• (Some carbon bonds are drawn longer, but are actually the same length.)
Review
• Work through the Sample Problem page 175
• Complete the revision questions page 175 (1 – 3)
Timberlake LecturePLUS 15
Learning Check Alk1
A. What is the condensed formula for H H H H
H C C C C H
H H H H
B. What is its molecular formula?C. What is its name?
Timberlake LecturePLUS 16
Solution Alk1
A. CH3CH2CH2CH3
B. C4H10
C. butane
17
Reactions of Alkanes
• Alkanes burn in oxygen to form carbon dioxide and water - oxidation or combustion reaction
• CH4(g) + O2(g) CO2(g) + 2H2O(g)
• Alkanes react with chlorine or fluorine in a reaction called a substitution reaction (one of the chlorine or fluorine atoms takes the place of one or more of the hydrogen atoms
Timberlake LecturePLUS 18
Reactions of Alkanes
Combustion
alkane + O2 CO2 + H2O + heat
Timberlake LecturePLUS 19
Combustion In the Cell
Metabolic oxidation is combustion
C6H12 O6 + 6O2 6CO2 + 6H2O + heat
glucose
Timberlake LecturePLUS 20
Learning Check Alk2
Complete the combustion reaction for
C3H8 + O2 +
Balance your equation
Timberlake LecturePLUS 21
Solution Alk2
Step 1
C3H8 + O2 CO2 + H2O
Step 2
C3H8 + O2 3 CO2 + 4 H2O
Step 3
C3H8 + 5 O2 3 CO2 + 4 H2O
Timberlake LecturePLUS 22
Learning Check Alk3
Complete and balance the reaction for the complete combustion of C7H16
Timberlake LecturePLUS 23
Solution Alk3
Step 1
C7H16 + O2 CO2 + H2O
Step 2
C7H16 + O2 7 CO2 + 8 H2O
Step 3
C7H16 + 11 O2 7 CO2 + 8 H2O
Review
• Complete the revision questions page 175 (4 - 6)
Isomers• Straight chain alkanes: An alkane that has all its carbons connected in a row.• Branched chain alkanes: An alkane that has a branching connection of carbons.• Isomers: Compounds with same molecular formula but different structures.
• There is only one possible way that the carbons in methane (CH4), ethane (C2H6), and propane (C3H8) can be arranged.
• However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.
29
Butane
Different isomers are completely different compounds. They have different structures, different physical properties such as melting point and boiling point, and may have different physiological properties.
Timberlake LecturePLUS 31
Review
• Complete revision questions page 176 (7 – 9)