Organic Chemistry

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Organic Chemistry

• Organic Chemistry The chemistry of carbon
• and carbon-based compounds

Organic Chemistry in everyday life Smells
tastes fruits, chocolate, fish,
mint Medications Aspirin, Tylenol,
Decongestants, Sedatives Addictive substances
Caffeine, Nicotine, Alcohol, Narcotics Hormones/Ne
urotransmitters Adrenaline, Epinephrine Food/Nut
rients Carbohydrates, Protein, Fat,
Vitamins Genetics DNA, RNA Consumer products
Plastics, Nylon, Rayon, Polyester
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Drawing Organic Structures
Shortcuts make structures easier faster to draw

• Butane C4H10

Lewis Structure
Carbon Atoms

• Line Structure
• Only shows bonds
• C atoms assumed at each end and intersection of
  bonds
• H atoms not shown
• Assume 4 bonds to each C
• Fulfill Cs 4 bonds by adding Hs

Condensed Structures
CH3CH2CH2CH3
CH3(CH2)2CH3
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Types of Organic Compounds

• Classified according to functional group

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Big Idea in Organic Chemistry

• Structure controls Function

Each functional group has predictable reactivity
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Alkanes or Paraffins

• All C atoms are tetrahedral and sp3 hybridized
  (only C-C single bonds)
• General formula CnH2n2 (CH4, C2H6, C3H8,
  C4H10, etc.)
• Can have linear or branched alkanes

C5H12
1
3
2

• Same molecular formula, different structure
  structural isomers
• Branches are called substituents
• Primary (1) carbon atom bound to one other C
  atom
• Secondary (2) C atom bound to 2 other C atoms
• Tertiary (3) C atom 3
• Quaternary (4) C atom 4

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Names of Linear Alkanes and Alkyl Substituents
of C atoms

• Alkane

Alkyl substituents
CH4 CH3CH3 CH3CH2CH3 CH3CH2CH2CH3
Methyl Ethyl Propyl etc.
Methane Ethane Propane Butane Pentane Hexane Hepta
ne Octane Nonane Decane
-CH3 -CH2CH3 -CH2CH2CH3
1 2 3 4 5 6 7 8 9 10
Root number of C atoms Suffix functional group
(-ane for alkanes) (-yl
for alkyl groups)
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Methane CH4
Butane C4H10
Methyl -CH3
Butyl -C4H9
Where R any other C atom or arrangement of C
atoms
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First Ten Hydrocarbons Properties
Number of Carbon Atoms
Molecular Formula
Melting Point, oC
of Isomers
Boiling Point, oC
Name

• -182.5
• -183.2
• -187.7
• -138.3
• -129.7
• 95.3
• 90.6
• 56.8
• 53.6
• 29.7

• -161.5
• -88.6
• -42.1
• -0.5
• 36.1
• 68.7
• 98.4
• 125.7
• 150.8
• 174.0

• 1
• 1
• 1
• 2
• 3
• 5
• 9
• 18
• 35
• 75

Methane Ethane Propane Butane Pentane Hexane
Heptane Octane Nonane Decane
1 2 3 4 5 6 7 8 9 10
CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18
C9H20 C10H22
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Properties of Alkanes
Nonpolar ? only London Dispersion Forces IMF
Larger molecular weight ? Stronger London
dispersion forces

• Compound
• Methane
• Ethane
• Propane
• Butane
• Pentane

MW 16 30 44 58 72
Boiling point (C) -164 -88.6 -42.1 -0.5 36.0
Formula CH4 C2H6 C3H8 C4H10 C5H12
Linear Alkanes 1 - 4 C atoms gas at room temp 5
- 15 C atoms liquid at room temp gt15 C atoms
solid at room temp
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Fractional Distillation of Crude Oil
Kelter, Carr, Scott, Chemistry A World of Choices
1999, page 429
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Naming Branched Alkanes (IUPAC)
4-ethyl
Octane
4-ethyl-3,5-dimethyloctane
2
8
3
5
6
4
1
7
3,5-dimethyl
3-methyl and 5-methyl

• Root name name of longest continuous C chain
  (parent chain)
• 2 equally long? Choose the one with more
  branches
• Number C atoms in chain, starting at end with
  first branch
• Identify substituents, give each a number (C it
  is connected to)
• Two or more identical substituents use prefixes
  (di-, tri-, tetra-, etc.)
• List substituents alphabetically before root name
• Do not alphabetize prefixes
• Punctuation commas separate numbers from each
  other
• hyphens separate numbers from names
• no space between last substituent root name

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Common Names of other Alkyl Substituents
Remember that R any carbon chain
R
isopropyl
alphabetized as i
iso indicates symmetry
R
isobutyl
alphabetized as i
2o
R
2o
sec-butyl
alphabetized as b
3o
3o
tert-butyl
alphabetized as b
R
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Naming Practice
Expanded Structure
Line Structure
2 - methylbutane
butane
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Naming Practice
H
H
C
C
C
H
Line Structure
H
H
H
C
C
H
H
H
C
H
H
hexane
4,4-dimethyl
hexane
3,3-dimethyl
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Isomers
The fat dog shook himself, and then rolled over
on the wet rug.
OR
The dog shook the fat rug, then rolled over and
wet on himself.
These two statements use the same words... but
have very different meanings!
Likewise, isomers may have the same formula, but
have very different structures
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Structural Isomers of C4H10
2-methylpropane or
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Structural Isomer Practice

• On piece of your own paper, draw AND name ALL of
  the isomers for the following alkanes

isomers
Formulas
C5H12 C6H14 C7H16
Pentane Hexane Heptane
3 5 9
Some of your drawings may look different, but
they are only different structures (isomers) if
they also have different names
If you complete that, try to draw and name all of
the isomers for octane (C8H18). There are 18 of
them!
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Structural Isomers Pentane (C5H12)
pentane
2-methylbutane
2,2-dimethylpropane
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Structural Isomers Hexane (C6H14)
hexane
2,3-dimethylbutane
2-methylpentane
2,2-dimethylbutane
3-methylpentane
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Structural Isomers Heptane (C7H16)
heptane
2,2-dimethylpentane
2-methylhexane
2,3-dimethylpentane
3-methylhexane
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Structural Isomers Heptane (C7H16)
2,4-dimethylpentane
3-ethylpentane
3,3-dimethylpentane
2,2,3-trimethylbutane
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Comparing Structural Isomers
(Same formula, different structure)

• C5H12

Name
Structure
Boiling point (C)
36.0
pentane
27.9
2-methylbutane
9.5
2,2-dimethylpropane
More branching ? weaker London dispersion forces
BP/MP of Linear alkanes gt BP/MP of branched
alkanes
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Reactions of Alkanes

• Combustion
• exothermic reaction
• alkanes used as fuel source

13/2
4
5
C4H10 ___ O2 ? ___ CO2 ___ H2O

• Incomplete Combustion with insufficient O2
  produces CO
• Poor ventilation, cigarettes

9/2
4
5
C4H10 ___ O2 ? ___ CO ___ H2O
CO is poisonous because it binds to the
hemoglobin in the blood, preventing the
absorption of O2