Organic Chemistry

1
Organic Chemistry

• Chapter 22

2
Vocabulary

• Organic Chemistry
• Hydrocarbons
• Saturated
• Unsaturated
• Alkanes
• Alkenes
• Alkynes
• Cis-trans isomerism

• Carbonyl group
• Ketones
• Aldehydes
• Carboxylic acids
• Carboxyl group
• Ester
• Ether
• Amine

3
Saturated vs. UnsaturatedHydrocarbons

• Hydrocarbons are molecules composed of carbon
  hydrogen
• Each carbon atom forms 4 chemical bonds
• A saturated hydrocarbon is one where all C - C
  bonds are single bonds the molecule contains
  the maximum number of H-atoms
• An unsaturated hydrocarbon is one where at least
  1 CC bond is double.

4
Straight-Chain Alkanes

• Straight-chain alkanes contain any number of
  carbon atoms, one after the other, in a chain
  pattern - meaning one linked to the next (not
  always straight)
• C-C-C C-C-C-C etc.

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Alkanes

• Hydrocarbon chains where all the bonds between
  carbons are SINGLE bonds
• Name uses the ending ane
• Examples Methane, Propane, Butane, Octane,
  2-methylpentane
• Formula (CnH2n2)

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Prefixes for of Carbons
1 Meth 6 Hex
2 Eth 7 Hept
3 Prop 8 Oct
4 But 9 Non
5 Pent 10 Dec
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Writing/drawing compounds
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Normal vs Branched Alkanes

• NORMAL alkanes consist of continuous chains of
  carbon atoms
• Alkanes that are NOT continuous chains of carbon
  atoms contain branches
• The longest continuous chain of carbons is called
  the parent chain

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Endings

• Attached carbon groups (substituents) end in yl
• Methyl CH3 -
• Ethyl CH3CH2-
• Propyl CH3CH2CH2     

3-ethylpentane
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Names of branches

• Carbon (alkyl) groups
• Methyl CH3 -
• Ethyl CH3CH2-
• Propyl CH3CH2CH2
• Halogens
• Fluoro (F-)
• Chloro (Cl-)
• Bromo (Br-)
• Iodo (I-)

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Branched-Chain Alkanes

• Rules for naming
• 1. Longest C-C chain is parent
• 2. Number so branches have lowest
• 3. Give position number to branch
• 4. Prefix (di, tri) more than one branch
• 5. Alphabetize branches (not prefix)
• 6. Use proper punctuation ( - and , )

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Some Simple Alkanes

• 2-methylpentane
• 3-ethylhexane
• 2,2-dimethylbutane
• 2,3-dimethylbutane

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Branched-Chain Alkanes

• From the name, draw the structure, in a
  right-to-left manner
• 1. Find the parent, with the -ane
• 2. Number carbons on parent
• 3. Identify substituent groups (give lowest
  number) attach
• 4. Add remaining hydrogens

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• 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.

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Your Turn

• Draw all possible structural isomers of C5H12

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Structural Isomerism

• Structural isomers are molecules with the same
  chemical formulas but different molecular
  structures

n-pentane, C5H12
2-methlbutane, C5H12
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IUPAC Rules for Naming Branched Alkanes

• Find and name the parent chain in the hydrocarbon
  - this forms the root of the hydrocarbon name
• Number the carbon atoms in the parent chain
  starting at the end closest to the branching
• Name alkane branches by dropping the ane from
  the names and adding yl. A one-carbon branch
  is called methyl, a two-carbon branch is
  ethyl, etc
• When there are more than one type of branch
  (ethyl and methyl, for example), they are named
  alphabetically
• Finally, use prefixes to indicate multiple
  branches

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Example 1 2,2-dimethylpentane

• The parent chain is indicated by the ROOT of the
  name - pentane. This means there are 5 carbons
  in the parent chain.

• dimethyl tells us that there are TWO methyl
  branches on the parent chain. A methyl branch is
  made of a single carbon atom.
• 2,2- tell us that BOTH methyl branches are on
  the second carbon atom in the parent chain.

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Example 2 3-ethyl-2,4-dimethylheptane

• The parent chain is indicated by the ROOT of the
  name - heptane. This means there are 7 carbons
  in the parent chain.

• 2,4-dimethyl tells us there are TWO methyl
  branches on the parent chain, at carbons 2 and
  4.
• 3-ethyl- tell us there is an ethyl branch
  (2-carbon branch) on carbon 3 of the parent
  chain.

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Example 3 2,3,3-trimethyl-4-propyloctane

• The parent chain is indicated by the ROOT of the
  name - octane. This means there are 8 carbons
  in the parent chain.

• 2,3,3-trimethyl tells us there are THREE methyl
  branches - one on carbon 2 and two on carbon 3.
• 4-propyl- tell us there is a propyl branch
  (3-carbon branch) on carbon 4 of the parent
  chain.

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Example 4 Name the molecules shown!

• parent chain has 5 carbons - pentane
• two methyl branches - start counting from the
  right - 2 and 3
• 2,3-dimethylpentane

• parent chain has 8 carbons - octane
• two methyl branches - start counting from the
  left - 3 and 4
• one ethyl branch - 5
• name branches alphabetically

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Alkenes Alkynes

• Alkenes are hydrocarbons that contain at least
  one carbon-carbon double bond
• Alkynes are hydrocarbons that contain at least
  one carbon-carbon triple bond

• The suffix for the parent chains are changed from
  ane to ene and yne
• e.g. ethene, propyne
• the BONDS are numbered like branches so that the
  location of the multiple bond may be indicated

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Alkenes Alkynes Examples
ethene
ethyne
propene
propyne
butene
2-pentyne
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Aromatic Hydrocarbons Cycloalkanes

• A cycloalkane is made of a hydrocarbon chain that
  has been joined to make a ring.

• Note that two hydrogen atoms were lost in forming
  the ring!

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Aromatic Hydrocarbons Cycloalkanes

• The two ends of the carbon chain are attached in
  a ring in a cyclic hydrocarbon
• named as cyclo- ____

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Aromatic Hydrocarbons

• Benzene is a six-carbon ring, with alternating
  double and single bonds

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Aromatic Compounds and Benzene

• Aromatic compounds contain benzene.
• Benzene, C6H6 , is represented as a six carbon
  ring with 3 double bonds.
• Two possible resonance structures can be drawn
  to show benzene in this form.

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Aromatic Hydrocarbons

• Benzene derivatives can have two or more
  substituents
• 1,2-dimethylbenzene
• 1,3-dimethylbenzene
• 1,4-dimethylbenzene
• Can use ortho for 1,2 meta for 1,3 and para for
  1,4 (page 711)

C
C
C
C
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Isomers

• With organic compounds

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Isomers

• There is a lack of rotation around a carbon to
  carbon multiple bond
• Two possible arrangements
• 1. trans configuration - substituted groups on
  opposite sides of double bond
• 2. cis configuration - same side

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Geometric Isomers
Substituted groups are on opposite sides of the
double bond (in this case, one is above, the
other is below)
Trans-2-butene
Substituted groups are on the same side of the
double bond (in this case, both are above)
Cis-2-butene
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Cis-Trans Isomers - Examples
cis-1,3-dimethylcyclobutane
cis-1,2-dichlorocyclohexane
trans-1-ethyl-2-methylcyclopropane
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Reactions

• With organic compounds

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Alkanes

• 1. Combustion reactions
• 2C2H6(g) 7O2(g) ? 4CO2(g) 6H2O(g)
• 2. Substitution reactions
• CH4 Cl2 ? CH3Cl HCl
• Methane chloromethane
• 3. Dehydrogenation reactions
• CH3CH3 ?CH2CH2 H2
• Ethane ethene

hv
500C
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Alkenes Alkynes

• 1. Addition reactions
• a. Hydrogenation
• CH2 CHCH3 H2 ? CH3CH2CH3
• Propene Propane
• b. Halogenation
• CH2 CHCH2CH2CH3 Br2 ? CH2 BrCHBrCH2CH2CH3
• Pentene 1,2-dibromopentene
• c. Polymerization
• Small molecules large molecules

Catalyst
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Aromatic

• 1. Substitution reactions
• Cl2 ? HCl

Catalyst FeCl3
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Functional Groups

• With organic compounds

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Functional Groups

• Functional group an atom or group of atoms
  within a molecule

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Functional Groups
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Alcohols

• contain an -OH (hydroxyl) group

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Halides Carboxylic Acids

• contain an -X (Halogen) group
• F, Cl, Br, I, At
• contain a carboxyl (-COOH) group

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Aldehydes and Ketones

• contain a carbonyl (CO) group

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Amines

• contain an amino group nitrogen bonded to one,
  two, or three carbon atoms
• an amine may by 1, 2, or 3

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Esters Ethers

• Ester trapped carboxylic acid
• Ether Trapped oxygen

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Branches
CnH2n2 Alkane CnH2n1 Alkyl group
CH4 methane CH3 Methyl
C2H6 ethane C2H5 ethyl
C3H8 propane C3H7 propyl
CH3CHCH3 methylethyl
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Naming
47
Naming
-O-
R-O-R
ether
ethoxyethane
48
Naming
RNH2
methanamine
-NH2
amine
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Naming