Organic Chemistry

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Unit 5

• Organic Chemistry

2

• The most important hypothesis in all of
• biologyis 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 (1918-1988)

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Organic Chemistry and Hydrocarbons

• Organic originally referred to any chemicals
  that came from organisms
• 1828 - German chemist Friedrich Wohler
  synthesized urea in a lab
• Today, organic chemistry is the chemistry of
  virtually all compounds containing the element
  carbon

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Allotropes of carbon

• Carbon exists naturally in three forms
• Graphite
• Diamonds
• Fullerenes

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Organic Chemistry and Hydrocarbons

• Over a million organic compounds, with a dazzling
  array of properties
• Why so many? Carbons unique bonding ability!

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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

Straight chain alkanes

• Contain any number of carbons atoms, one after
  the other, in a chain. Each carbon atoms is
  bonded to 1 or 2 other carbon atoms.

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Complete Structural Formulas

• Show the bonds between each of the atoms
• H H
• ? ?
• H ? C ? H H C H
• ? ?
• H H
• CH4 , methane

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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

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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

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IUPAC NAMES

• Name carbons Structural Formula
• Hexane 6
  CH3CH2CH2CH2CH2CH3
• Heptane 7 CH3CH2CH2CH2CH2CH2C
  H3
• Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3
  
• Nonane 9 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
• H H H 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 O2 CO2 H2O heat

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Combustion In the Cell

• Metabolic oxidation is combustion
• C6H12 O6 6O2 6CO2 6H2O heat
• glucose

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Learning Check Alk2

• Complete the combustion reaction for
• C3H8 O2
• Balance your equation

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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

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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 O2 CO2 H2O
• Step 2
• C7H16 O2 7 CO2 8 H2O
• Step 3
• C7H16 11 O2 7 CO2 8 H2O

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Branched chain alkanes

• Occur when a carbon atoms bonds with three or
  four carbon atoms.

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Branched chain alkanes

• Substituents take place of a hydrogen atom on a
  parent hydrocarbon.

substituent
c c c c c c
c c c c c c c
Parent alkane (propane)
Parent alkane (hexane)
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Hydrocarbon substituents

• Are called alkyl group
• Name ending with yl
• Methyl group (CH3-)
• Ethyl group (CH3CH2-)
• Propyl group (CH3CH2CH2-)

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Rules for naming branched alkanes

1. Find the longest chain of carbons in the molecule
   or parent chain. (not necessarily a straight
   line)

2. Number the carbons in parent chain. Start at
the end that will give the groups attached to the
chain the smallest numbers.
3. Identify with numbers the positions of the
substituents on the chain.
4. Use prefixes to indicate the appearance of
the same group more than once di- (twice), tri-
(three times)
5. List the names of the substituents groups in
alphabetical order.
6. Commas separate numbers, hyphens separate
numbers and words. Name is written without spaces
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Ex. 1 Name the following alkane

• CH3 CH2 CH CH3
• CH3

1
2. Number parent chain in a way that
substituents have smallest numbers.
2- methyl (located in carbon 2)
3. Identify position of substituent group and
name it.
4. Not applicable
6. Separate letters and numbers with hyphen
5. List substituent groups in alphabetical order.
butane
2-methyl
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Ex.2 CH3 CH CH2 CH2 CH3
CH2
CH3
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Ex.2 CH3 CH CH2 CH2 CH3
CH2
CH3

• Parent alkane

• Does not have to be a straight line, only longest
  chain.

• Name of parent alkane hexane

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

• Number Parent alkane

• Number in way that substituent group has smallest
  number.

• Name and position of substituent group 3-methyl

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

• Name of organic compound

• 3-methylhexane

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Cw p 226 1
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Writing structural formulas

• Write the complete structural formula for
• 2,2-dimethylpropane

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Writing structural formulas

• Write the complete structural formula for
• 2,2-dimethylpropane

Write only the carbons first. Start with the
parent alkane.
2,2-dimethylpropane
C C C
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Writing structural formulas

• Write the complete structural formula for
• 2,2-dimethylpropane

Number the parent alkane from left to right.
C C C
1
2
3
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Writing structural formulas

• Write the complete structural formula for
• 2,2-dimethylpropane

Identify the substituent groups and their
position
2,2-dimethylpropane
There are two (di) methyl groups (CH3-) in carbon
2
CH3 C
C C
CH3
1
2
3
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Writing structural formulas

• Write the complete structural formula for
• 2,2-dimethylpropane

Add the necessary hydrogen bonds so that each
carbon has a maximum of 4 bonds.
H CH3 H H C
C C H H
H
CH3
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Classwork p226 2,3
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Isomers

• Are compounds that have the same molecular
  formula but different structural formulas.
• Have different physical properties, like boiling
  point and melting point and different chemical
  reactivities.

• Ex. C4H10

CH3 CH2 CH2 CH3
butane
CH3 CH CH3 CH3
2-methylpropane
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Classwork

• Draw and name the isomers for the organic
  compounds with the following molecular formulas
• a)C5H12 (3 different structures)
• b) C6H14 (5 different structures)