Organic Reactions

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Organic Reactions
Reaction of Amines with Carbonyl Compounds
Question: How do organic amines react with compounds having
a carbonyl group?1
Background Reading: Study the sections in your textbook covering the following topics:
1. Amines
2. Carbonyl Groups
3. Polymers
I. The Reaction of Aniline with Acetic Anhydride
A. About the Reactants
The Lewis Structures of the two reactants for this reaction, aniline and acetic anhydride, are given below.
Aniline is called an amine because it has a nitrogen atom in it. Acetic anhydride has carbon double bonded to
oxygen within it; these two atoms bonded that way are called a carbonyl group. You will react these two
together in aqueous solution and identify the product by its physical properties. You will be using hydrochloric
acid to help dissolve the aniline and later add the weakly basic acetate anion to free up the aniline and allow it
to react.
B. Running the Reaction
Using graduated cylinders, put 25.0 mL of 0.4 M HCl (aq) into a 100 mL beaker. Put 7 to 8 mL of 1.9 M
sodium acetate, NaC2H302 (aq), into a separate small beaker.
Add 0.5 mL of aniline from the buret setup in the lab to the 25.0 mL HCl solution and stir until it is all
dissolved. After the aniline dissolves, as one partner stirs, the other is to add 0.7 mL of acetic anhydride from
another buret set up in the lab, then immediately add the 7 mL of 1.9 M NaC2H302 (aq). Continue stirring until
a change occurs. Record your observations in your notebook.
Dispose of the product and left over solution in the appropriately labeled waste container in the hood.
1
Adapted from Inquiries into Chemistry by M. R. Abraham and M. J. Pavelich.
Larson/Daley
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Organic Reactions.doc
Reaction of Amines with Carbonyl Compounds
II. The Reaction Between 1,6-Hexanediamine and Adipoyl Chloride2
A. About the Reactants
The Lewis Structures of the two reactants for the second reaction, 1,6-hexanediamine (also called
hexamethylenediamine) and adipoyl chloride are given. These have been dissolved in water and in hexane,
respectively, for you. These two solvents are immiscible with
each other so that the reaction is forced to occur at their
interface. The hexamethylenediamine is in excess during this
reaction
B. Running the Reaction
Put 10 mL of 0.5 M 1,6-hexanediamine into a 50 mL beaker.
(Note, the 1,6-hexanediamine solution has been made basic by
adding NaOH.) Into a separate beaker, measure out 10 mL of
0.2 M adipoyl chloride in hexane. [The stockroom may substitute sebacoyl chloride in place of the adipoyl
chloride. Sebacoyl chloride has on extra CH2 group in the center chain, -(CH2)5- PLEASE CHECK the LABEL.]
Pour this gently down the side of the other solution. Do not mix. Let stand for a few minutes and observe.
What does the interface between the two liquids look like? Test the vapor above the reactants with a strip of
pH paper by holding the pH paper directly above the liquid in the beaker. Record all of your observations in
your notebook.
Using tongs or forceps, grab the opaque material at the interface of the two solutions and slowly pull it up out
of the solution. Continue to pull, winding the material around a stirring rod or spatula. When you have a foot
or two of it, break the string and wash the wound material with water, catching the wash in a waste beaker.
Investigate the texture of the material using a gloved hand. Record your observations in your notebook.
Mix the remaining solution. Wash the resulting material with water, catching the wash in a waste beaker.
Investigate the texture of the material using a gloved hand. Record your observations in your notebook.
Dispose of the product and wash in the appropriately labeled waste container located in the hood.
2
The stockroom may substitute sebacoyl chloride in place of the adipoyl chloride. Sebacoyl chloride has an
extra CH2 group in the center chain.
Larson/Daley
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April 4, 2009
Organic Reactions.doc
Reaction of Amines with Carbonyl Compounds
Name:
Lab section MW or TTh
Locker #
Partner:
Report Sheet: Reaction of Amines with Carbonyl Compounds
I. The Reaction of Aniline with Acetic Anhydride
A.
Identify the Crystals
Consult the list of organic compounds and their properties in Table I. What is the most likely identity
of the product crystals? Give the Lewis Structure for this compound. Explain in terms of molecular
structure (Lewis Structure) AND physical properties why you chose it.
B.
A Reaction Mechanism
Using Lewis Structures and arrows, draw a picture of how aniline probably reacted with acetic
anhydride. What other product most likely formed? Hint: Think about what bonds are broken and what
bonds are formed in the reaction. Also, consider the polarity of bonds and the fact that opposite
charges attract.
C.
Speculate on where the electrons in the new bond formed in the product crystals came from.
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Organic Reactions.doc
Reaction of Amines with Carbonyl Compounds
II. The Reaction of 1,6-hexanediamine with Adipoyl Chloride.
A.
Speculate on what the chemical formula is for this new material. Use the mechanism (the reaction
picture) you developed and the description you gave in part I.B to speculate on how the amine parts
of 1,6-hexanediamine may have reacted with the carbonyl parts of adipoyl chloride (i.e., give a
possible Lewis Structure for the product of the reaction and briefly explain why you chose that
structure).
B.
What small molecule is eliminated in this reaction? What experimental evidence do you have to
support your answer?
C.
Offer a COMPLETE explanation for the difference in physical properties of the two materials made in
this experiment (i.e., why is one discrete small crystals while the other is a continuous string?). Hint:
Look at both ends of the 1,6–hexanediamine and adipoyl chloride molecules.
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Organic Reactions.doc
Reaction of Amines with Carbonyl Compounds
Name
Table I: Organic Compounds, Lewis Structures and Properties
Lewis Structure*
Properties
Octyl acetate
Odor of oranges
Boil pt. = 210 °C
Iso amyl-acetate
Odor of bananas
Boil pt. = 142 °C
Ethyl butanoate
Odor of pineapples
Boil pt. = 110 °C
Aniline
Biting odor
Boil pt. = 184 °C
Acetanilide
Shiny, plate-like crystals
in water
Melt pt. = 114 °C
Benzamide
Crystalline
Soluble in water
Melt pt. = 132 °C
* C– indicates a C–H bond
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Organic Reactions.doc

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