Download Chemistry Crunch #12.2: Organic Reactions KEY Why? Learning

Chemistry Crunch #12.2: Organic Reactions KEY
Why?
Many organic reactions lead to products we use everyday. Organic reactions can be categorized
by looking at the reactants used and the products formed. Soap, alcohol, fragrances, flavors,
and flames in your gas barbeque are all products of organic reactions.
Learning Objectives:
Recognize organic reactions:
○ Substitution
○ Addition
○ Esterification
○ Combustion
○ Fermentation
○ Saponification
SUCCESS will be Measured by YOUR Ability to:
Predict the products of organic reactions.
Prerequisites:
Writing chemical equations.
Ability to distinguish reactants and products in a reaction.
Naming and identifying organic compounds.
Ability to distinguish between saturated and unsaturated hydrocarbons.
Naming and recognizing functional groups in organic compounds.
Vocabulary:
• Substitution
• Addition
• Fermentation
• Saponification
• Combustion
• Esterification
Model 1: Substitution
Key Questions:
1. Circle the reactants and square the products in the reaction above. What compound category do each
of the reactants belong to?
ethane = hydrocarbon
Cl2 = diatomic element
2. Describe what happened in the substitution reaction.
One chlorine switches with one Hydrogen from ethane.
Exercises:
1. Draw and name the products of the substitution reaction between methane and bromine.
Bromomethane
Hydrogen bromide
2. Describe what happens in the substitution reaction that involves methane and bromine molecules.
One hydrogen from the methane switches with one bromine.
3. Summarize. In a characteristic substitution reaction:
a) There will always be 2 reactant(s) and 2 product(s).
(give a #)
(give a #)
b) Describe a substitution reaction in general terms (meaning without referencing any specific
elements or any specific reaction).
One element from each reactant switches places.
Model 2: Addition
Key Questions:
1. How are the reactants in this reaction similar to those in the substitution reaction?
It still contains a hydrocarbon and diatomic molecule.
2. How are the reactants in this reaction different from those in the substitution reaction?
The hydrocarbon has a double bond (unsaturated).
3. What type of organic compound is the reactant in the addition reaction? Alkene
4. Describe what happens in the addition reaction. The double bond is broken and a chlorine is
added to each carbon that previously had the double bond.
5. Suggest at least two other diatomic elements that could replace chlorine in an addition reaction.
BrINClHOF: H2, Br2, O2, F2, I2, N2
Exercises:
1. Draw and name the products of the addition reaction between pentene and hydrogen.
2. Describe what is going on between the molecules of pentene and hydrogen in this addition reaction.
The double bond is broken and H’s are added to each Carbon which previously had a
double bond.
3. Summarize. In a characteristic addition reaction:
a) There will always be 2 reactant(s) and 1 product(s).
b) The hydrocarbon reactant will always have a double or triple bond, or in other words, the
hydrocarbon will be unsaturated.
c) We learned how to classify many non-organic chemical reactions. Which one of these will an
organic addition reaction resemble?
synthesis
d) Describe an addition reaction in general terms.
An alkene or alkyne has a diatomic element added to it breaking the double or triple bond
producing one product. (An unsaturated hydrocarbon becomes saturated.)
Model 3: Combustion
Key Questions:
1. Circle the reactants and square the products in the reaction above. What compound category does
the first reactant belong to?
hydrocarbon (alkane)
2. Describe what happened in the combustion reaction.
Propane reacts (burns) with oxygen to produce CO2 and H2O.
Exercises:
1. Propane is an alkane, hexene is an alkene, and butyne is an alkyne.
a) What would be the products of the combustion equation for each of these compounds? Explain
your answer.
CO2 and H2O are ALWAYS produced in a combustion reaction.
b) Would the amounts of the products be the same for your answer to 1a? Explain.
No! Depending on how big or small the hydrocarbon is, a different amount of CO2
and H2O would be produced.
2. Write the balanced equation for the complete combustion of hexene (C6H12).
1 C6H12 + 9 O2
6 CO2 + 6H2O
3. Summarize. In a characteristic combustion reaction:
a) There will always be 2 reactant(s) and 2 product(s).
(give a #)
(give a #)
b) What is the only thing that will change from one combustion reaction to another?
The amount of CO2 and H2O produced.
c) Describe a combustion reaction in general terms.
Hydrocarbon + O2
CO2 + H2O
A hydrocarbon reacts in the presence of oxygen to produce carbon dioxide and water.
Model 4: Esterification
Esters produce pleasant odors. Many compounds naturally found in fruits can be prepared in the laboratory using
an esterification reaction and are then used in candies and perfume.
Reactant 1
Reactant 2
Key Questions:
1. To what class of organic compounds does reactant 1 belong?
organic acid
2. To what class of organic compounds does reactant 2 belong?
alcohol
3. To what class of organic compounds does the product (not water) belong? ester
Exercises:
1. Draw a structural formula for each of the reactants in the reaction below.
butanoic acid
+
1-pentanol
X +
water
2.Identify
Identify(name)
(name)and
anddraw
drawproduct
productX.
X.
2.
pentyl butanoate
3. Summarize. In a characteristic esterification reaction:
a) There will always be 2 reactant(s) and 2 product(s).
(give a #)
(give a #)
b) The H from the organic acid and the OH from the alcohol join to make water and an ester.
They are joined at the place the water was removed. The removal of water is also known as
dehydration.
c) Describe an esterification reaction in general terms.
An organic acid and alcohol join to produce an ester and water.
Model 5: Fermentation
Key Questions:
alcohol
1. Ethanol is an example of what type of organic compound?
2. What is the role of the “yeast/zymase” in the fermentation reaction?
It is the catalyst (gets the reaction going).
Exercise:
1. Summarize. In a characteristic fermentation reaction:
a) There will always be 1 reactant(s) and 2 product(s).
(give a #)
(give a #)
b) We learned how to classify many non-organic chemical reactions. Which one of these will an
decomposition
organic fermentation reaction resemble?
c) Describe a fermentation reaction in general terms.
In the presence of yeast (a catalyst) sugar will break down producing alcohol and CO2.
Model 6: Saponification
**NOTE: SAPOnification looks like SOAP!!
Exercises:
1. What are the characteristic features of a saponification reaction?
A fat and base react producing soap and glycerin.
2. We learned how to classify many non-organic chemical reactions. Which one of these will an organic
saponification reaction resemble?
double replacement
3. If the Na in the soap molecule were to be replaced with H, what would be the classification of the
organic compound that forms?
organic acid