Organic Chemistry

1
Organic Chemistry

• Chapter 22

2
Organic Chemistry

• The study of carbon-containing compounds and
  their properties.
• The vast majority of organic compounds contain
  chains or rings of carbon atoms.

3
Organic Inorganic Compounds

• Originally the distinction between inorganic and
  organic substances was based on whether or not
  they were produced by living systems.
• In 1828, German chemist Friedrich Wohler prepared
  urea from the inorganic salt ammonium cyanate by
  simple heating
• heat
• NH4OCN ---gt NH2CONH2

4
Hydrocarbons

• . . . compounds composed of carbon and hydrogen.
• Saturated carbon-carbon bonds are all single -
  alkanes CnH2n2

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Hydrocarbons(continued)

• Unsaturated contains carbon-carbon multiple
  bonds.

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Hydrogen Addition

• C2H4(g) H2(g) ---gt C2H6(g)
• unsaturated saturated

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The carbon-hydrogen bonds in methane.
8
The Lewis structure, space-filling, and
ball- and-stick models for ethane.
9
The structures of propane and butane with
109.5o bond angles.
10
Structural Isomerism

• -- isomers contain the same atoms but one or more
  different bonds.

11
Normal butane (n-butane) and the branched
isomer, isobutane.
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Isomers of Pentane

• What are the three isomers of pentane?
• 1) n-pentane -- straight-chain
• 2) isopentane -- one branch from 2nd carbon
• 3) neopentane -- two branches from central carbon

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The straight-chain isomer, n-pentane.
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Rules for Naming Alkanes

• 1. For alkanes beyond butane, add -ane to the
  Greek root for the number of carbons.
• C-C-C-C-C-C hexane
• 2. Alkyl substituents drop the -ane and add
  -yl.
• -C2H5 is ethyl

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Rules for Naming Alkanes

• 3. Positions of substituent groups are specified
  by numbering the longest chain sequentially.
• C
• ??
• C-C-C-C-C-C
• 3-methylhexane
• 4. Location and name are followed by root alkane
  name. Substituents in alphabetical order and use
  di-, tri-, etc.
• See Sample Exercise 22.2 on pages 1062-1064.

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Combustion Reactions of Alkanes

• C3H8(g) 5O2(g) ----gt 3CO2(g) 4HOH(g)
• 2C4H10(g) 13 O2(g) ----gt 8CO2(g) 10HOH(g)

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Substitution Reactions for Alkanes

• Primarily where halogen atoms replace hydrogen
  atoms.

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Dehydrogenation Reactions

• Cr2O3
• CH3CH3 ----gt CH2CH2 H2
• 500oC
• ethane
  ethylene

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Cyclic Alkanes

• Carbon atoms can form rings containing only
  carbon-carbon single bonds.
• C3H6, C4H8, C6H12
• Shorthand notation for the cyclic alkanes.

20
The molecular structure of cyclopropane and the
overlap of the sp3 orbitals that form the C-C
bonds.
21
The chair and boat forms of cyclohexane.
22
Alkenes and Alkynes

• Alkenes hydrocarbons that contain a
  carbon-carbon double bond. CnH2n
• C?CC propene
• Alkynes hydrocarbons containing a carbon-carbon
  triple bond. CnH2n-2
• C?C?C?C?C 2-pentyne

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Nomenclature for Alkenes

• 1. Root hydrocarbon name ends in -ene
• C2H4 is ethene
• 2. With more than 3 carbons, double bond is
  indicated by the lowest numbered carbon atom in
  the bond.
• CC?C?C is 1-butene

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The bonding in ethylene.
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The two stereoisomers of 2-butene. a)
cis-2-butene b) trans-2-butene
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The bonding in ethane allows rotation and
no cis-trans isomerism.
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The bonding in acetylene.
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Addition Reactions

• . . . in which (weaker) ? bonds are broken and
  new (stronger) ? bonds are formed to atoms being
  added.

propene
propane
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Halogenation

• CH2CHCH2CH2CH3 Br2 ---gt CH2BrCHBrCH2CH2CH
  3
• 1-pentene 1,2-dibromopentane

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Aromatic Hydrocarbons

• A special class of cyclic unsaturated
  hydrocarbons.

Cl2
HCl
benzene
Chlorobenzene
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Aromatic Hydrocarbons
phenyl group
Ortho (o-) -- two adjacent substituents. meta
(m-) -- two substituents with one carbon between
them. para (p-) -- two substituents opposite
each other.
32
Refinery Processes

• Cracking large molecules broken down to smaller
  ones by breaking carbon-carbon bonds.
• Pyrolysis (thermal cracking) The process that
  produces cracking at high temperatures.
• Catalytic Cracking Cracking at lower
  temperatures.
• Catalytic reforming Alkanes and cycloalkanes
  converted to aromatic compounds.

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The Common Functional Groups

• Class General Formula
• Halohydrocarbons R?X
• Alcohols R?OH
• Ethers R?O?R?
• Aldehydes

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The Common Functional Groups

• Class General Formula
• Ketones
• Carboxylic Acids
• Esters
• Amines R?NH2
• Amides R-CONH2

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Alcohols

• contain the hydroxyl group (-OH).

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Aldehydes Ketones

• contain the carbonyl group ( CO ).
• In ketones the carbonyl group is bonded to two
  carbon atoms -- CH3COCH3.
• In aldehydes the carbonyl group is bonded to at
  least one hydrogen atom -- HCHO.

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Carboxylic Acids Esters

• Carboxylic acids contain the carboxyl group
• O
• (-C-OH).
• O
• Esters contain the -C-O- group.

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Amines Ethers

• Amines contain -NH2 group.
• If one hydrogen is removed and replaced with a
  hydrocarbon group, it is a primary amine.
• If two hydrogen are replaced, it is a secondary
  amine.
• If all three hydrogens are replaced, it is a
  tertiary amine.
• Ethers contain the -O- group.

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Polymers

• . . . are large, usually chainlike molecules that
  are built from small molecules called monomers.
• Monomer Polymer
• Ethylene Polyethylene
• Vinyl chloride Polyvinyl chloride
• Tetrafluoroethylene Teflon

41
Types of Polymerization

• Addition Polymerization monomers add together
  to form the polymer, with no other products.
  (Teflon)
• Condensation Polymerization A small molecule,
  such as water, is formed for each extension of
  the polymer chain. (Nylon)