Organic Chemistry

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Organic Chemistry
- Organic Reactions
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Organic Reactions

• We described hydrocarbons and looked at their
• structural isomers
• We reviewed how to name hydrocarbons and
  compounds
• containing functional groups

Were now going to focus on a several kinds
of Organic reactions
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Organic Reaction Types

• There are in fact so many types of organic rxns
• It would be impossible to review them all.
• Therefore were going to focus on just a few
• Substitution - Elimination
• Addition - Esterification
• - Fermentation - Saponification
• - Polymerization (Condensation Addition)

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Substitution Reactions

• Any reaction in which one atom is replaced by
  another
• Used to place a halogen onto an alkane
• The products always are a halocarbon and the acid
  of the halogen (ex hydrobromic acid)
• Needs ultraviolet light to initiate the reaction
• Provides the high energy needed to form the
  excited state

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Substitution Rxns
What is the products formed in the following rxn?
CH3CH3 Br2 ? sunlight
CH3 CH2Br HBr
(Why sunlight?)
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Elimination Rxns

• Any reaction in which atoms are eliminated from
  another molecule
• This can be done by
• Elimination of H2
• Elimination of HX
• Elimination of H20

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Elimination Reactions

• Loss of H2
• - This process is often referred to as
  Dehydrogenation

H H H-C-C-H ? H2CCH2 H2
H H
Heat, catalyst
This type of rxn takes place in industry in what
is know as a catalytic cracking unit
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Elimination Rxns

• Loss of HX
• Alkyl halides can also undergo elimination. This
  is as
• known as dehydrohalogenation

The base extract a proton (H) and X- leaves
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Elimination Rxns

• Loss of H2O
• Alcohols can undergo elimination via the loss of
  water.
• This is known as dehydration

a) The acid protonates the OH group, water
leaves Positive carbon remains behind b) An
adjacent proton (H) leaves next leaving the
electron pair to form the double bond
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Addition

• Takes place with unsaturated compounds which are
  usually more reactive that saturated compounds
• Takes place with both Double and Triple bonds
• Two atoms are added across the electron rich bond
• What can be added?
• X2
• H2
• H2O
• HX

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Addition

• Addition of halogen
• Normally occurs dissolved in a solvent such as
  CCl4
• Alkenes form dihaloalkanes
• Alkynes produce dihaloalkenes or tetrahaloalkanes

1,2-dichloroethane
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Addition

• Addition of Hydrogen
• Catalysts normally used such at Pt, Pd or Ni
• Known as Hydrogenation
• Alkene becomes an alkane
• Alkyne becomes and alkene or alkane

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Addition

• Addition of Water
• Occurs in the presence of acid (H)
• Known as Hydration
• Alkene becomes an alcohol
• Alkynes do not produce alcohols this way!
• (produces ketone or aldehyde)

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Addition

• Addition of Hydrogen Halides (HX)
• HX HCl, HBr, HI (Not HF)
• Alkene becomes an alkyl Halide
• Alkynes form Monohalo alkenes or dihaloalkanes
  with
• the halogens on the same carbon

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Esterification

• Alcohol Organic Acid Water Ester
• Used to make perfumes, scents and flavors
• Combination reaction which involves dehydration.
• The alcohol becomes the alkyl group and the acid
  becomes -oate

Methyl propanoate
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Aspirin Made by Esterification

?
Acetic acid
Salicylic Acid
(An alcohol and acid)
Acetyl Salicylic Acid (Common Name)
Aspirin
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Fermentation

• Fermentation is the process by which glucose is
  broken down by an enzyme (a catalyst) in the
  absence of oxygen into an alcohol and carbon
  dioxide
• One enzyme used is Zymase (Found in baker yeast)
• If Zymase is used the alcohol produced is ethanol
• The oldest chemical reaction practiced by man
• In place of glucose, starches from grains can be
  used. Hence the name grain alcohol

• 
  
  C6H12O6 ? 2C2H5OH 2CO2
• Glucose
  Ethanol Carbon dioxide

Zymase
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Saponification

• Another very old chemical reaction practiced by
  man
• The hydrolysis of the ester bonds (back to acid
  alcohol) in triglycerides using an aqueous soln
  of a strong base to form carboxylate salts and
  glycerol
• Hydrolysis of fats by a strong base (KOH or NaOH)
• Products are soap and glycerol (a triol)

O CH2-0H K
-O-C-(CH2)14CH3
O CH2-OH K -O-C-(CH2)14CH3
O CH2-0H K -O-C-(CH2)14CH3
3KOH ?

A TRIGYCERIDE
GLYCEROL 3 SOAP MOLECULES
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Polymers
The joining together of many smaller repeating
Units to form a very high MW molecule
- Polymers range from 10,000 amu to more
than 1,000,000 amu
The small repeating units used to build the
polymer are known as monomers
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Monomers
Sometimes just one monomer is used to make the
Polymer (example ethylene (a) to form
polyethylene)
And sometimes several monomers are used
(example adipic acid (a) and 1,6-diaminohexane
(b) to form nylon)
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Polymerization
There are two methods well quickly look at
for Forming Polymers. - Addition
polymerization - Condensation polymerization
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Addition Polymerization

• All the atoms present in the monomer are
• retained in the polymer
• This type of reaction involves monomers with
• double or triple bonds

• An initiator is required to produce a free
  radical
• A very reactive substance having a free e-
• Peroxides are typically used to produce this free
  radical

Peroxide ? Rad
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Free radical induced addition polymerization of
Ethylene to form polyethylene
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Free radical induced addition polymerization of
Propylene to form polypropylene
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Free radical induced addition polymerization of
Styrene to form polystyrene
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Condensation Polymerization

• Monomers that join together by the loss of
  water
• each monomer has two functional groups that are
• the same
• monomer 1 and monomer 2 functional groups
• are different
• reaction occurs between the two pairs of
• dissimilar functional groups

Lets look at some examples
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Condensation Polymerization - Dacron
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Condensation Polymerization - Nylon
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Were Done! You Made it to the End!