Chemistry 212
Fall 2009
Carbonyl Reactions - 4
Mechanisms for Substitution for an -Atom group in Carbonyl Compounds:
h.
H
H
O
C
C
O
CH3
+
H
H
O
C
C
OCH3
O
CH3
O
O
C
C
O
CH3 + HOCH
3
NOTE: Although a single step substitution mechanism such as the example to
the right seems to be inviting, it is not observed. As we have seen so far,
formation of a bond to a carbonyl carbon results in breaking the -bond between
O
O
the carbon and oxygen atoms. This can be understood by considering that the
electrons in -bonds have considerably higher energy than those in -bonds
C
C
CH3CH2OH
CH2
+ Cl
CH3
Cl
such as the C-Cl bond in the example. So when a pair of electrons adds to the
CH3
O
CH3
carbonyl carbon atom, there is a smaller increase in energy if the-electrons
H
become a lone pair on the oxygen atom than if the -electrons become a lone
pair on the chlorine atom.
As with the addition reactions consider in each case:
-> WHAT OVERALL CHANGE OCCURS (Bonds made and
-> WHERE ARE THE HIGHEST ENERGY ELECTRONS?
broken)? Illustrate on the given structures.
Circle on original structures.
-> HOW CAN THE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO BEGIN THE CONVERSION
OF THE REACTANTS TOWARD THE PRODUCTS? Propose a reaction step with original structures using arrows. Write
intermediate product structures below:
Carbonyl Reactions-4
-> NOW WHERE ARE THE HIGHEST ENERGY ELECTRONS? Circle on your new structures.
2
-> HOW CAN THESE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO MAKE AND BREAK
BONDS THAT WILL MOVE THE INTERMEDIATE STRUCTURES TOWARD THE PRODUCTS? Propose a reaction step with
your new structures using arrows. Write next intermediate product structures below:
Continue until you have reached the products.
3
Carbonyl Reactions-4
j.
O
O
f.
CH3
C
NH2
+
H3O
+
-> WHAT OVERALL CHANGE OCCURS (Bonds made and
broken)? Illustrate on the given structures.
CH3
->
+
C
H
O
+
NH4
WHERE ARE THE HIGHEST ENERGY ELECTRONS?
Circle on original structures.
-> HOW CAN THE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO BEGIN THE CONVERSION
OF THE REACTANTS TOWARD THE PRODUCTS? Propose a reaction step with original structures using arrows. Write
intermediate product structures below:
-> NOW WHERE ARE THE HIGHEST ENERGY ELECTRONS? Circle on your new structures.
-> HOW CAN THESE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO MAKE AND BREAK
BONDS THAT WILL MOVE THE INTERMEDIATE STRUCTURES TOWARD THE PRODUCTS? Propose a reaction step with
your new structures using arrows. Write next intermediate product structures below:
Continue until you have reached the products.
Carbonyl Reactions-4
4
Define the reaction conditions (acidic, basic, or neutral) for the three reactions in carbonyl reactions-4.
First reaction is basic, second reaction is acidic, third reaction is basic
What are the key aspects of the reactions that determined your conclusion?
We look at the high energy electrons. If they are present, it is a basic reaction. If there aren’t any but there is a low energy element that needs
electrons, it is acidic. If neither are present, it is neutral.
O
O
i.
CH3
C
Cl
+
2 CH3CH2OH
-> WHAT OVERALL CHANGE OCCURS (Bonds made and
broken)? Illustrate on the given structures.
CH3
->
C
O
CH2
+ Cl
CH3
+ CH3CH2OH2
WHERE ARE THE HIGHEST ENERGY ELECTRONS?
Circle on original structures.
-> HOW CAN THE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO BEGIN THE CONVERSION
OF THE REACTANTS TOWARD THE PRODUCTS? Propose a reaction step with original structures using arrows. Write
intermediate product structures below:
5
Carbonyl Reactions-4
-> NOW WHERE ARE THE HIGHEST ENERGY ELECTRONS? Circle on your new structures.
-> HOW CAN THESE HIGHEST ENERGY ELECTRONS BE USED IN A SIMPLE REACTION STEP TO MAKE AND BREAK
BONDS THAT WILL MOVE THE INTERMEDIATE STRUCTURES TOWARD THE PRODUCTS? Propose a reaction step with
your new structures using arrows. Write next intermediate product structures below:
Continue until you have reached the products.
Carbonyl Reactions-4
6
Out of Class Applications for Carbonyl reactions-4
A. Read: CGWW Chapters:
12 & 28
B. Try to apply your mechanism(s) to the other two examples of substitutions for carbonyl oxygen introduced in Carbonyl Rxns-1 and reproduced
below.
p.
O
O
H3 O +
H +
OH
+ H2 O
O
O
-> WHAT OVERALL CHANGE OCCURS?
->
WHERE ARE THE HIGHEST ENERGY ELECTRONS?
-> WHAT CAN THE HIGHEST ENERGY ELECTRONS DO TO AID IN THE NEEDED BOND MAKING AND BREAKING?
-> NOW WHERE ARE THE HIGHEST ENERGY ELECTRONS?
-> WHAT CAN THEY DO TO AID IN THE NEEDED BOND MAKING AND BREAKING?
Continue until you have reached the products.
r.
O
CH3
C
O
CH3
O
O
+
CH3 OH
C
CH3
+
C
O
CH3
CH3
C
O
H
O
-> WHAT OVERALL CHANGE OCCURS?
->
WHERE ARE THE HIGHEST ENERGY ELECTRONS?
-> WHAT CAN THE HIGHEST ENERGY ELECTRONS DO TO AID IN THE NEEDED BOND MAKING AND BREAKING?
-> NOW WHERE ARE THE HIGHEST ENERGY ELECTRONS?
-> WHAT CAN THEY DO TO AID IN THE NEEDED BOND MAKING AND BREAKING?
Continue until you have reached the products.
C. Text Applications:
Appropriate Questions:
CGWW Chapter 12: Problems 2-7 & 9-11
Chapter 28: Problems 2, 4, 6 & 7
7
D. Nomenclature of Esters
Carbonyl Reactions-4
References:
1. CGWW: pp. 37-44
2. Tutorials:
a.
http://chemistry.boisestate.edu/people/richardbanks/organic/nomenclature/organicnomenclature1.htm
Developed by Richard C. Banks, Professor of Chemistry, Boise State University
Section -> Esters (provides questions with answers)
b. http://www.molecularmodels.ca/nomenclature/index-2.htm
Developed by Professor Dave Woodcock, Okanagan University College, British Columbia, Canada
Sections: -> 5. Functional Groups with Suffix and Prefix -> VIII. Alkanoates (Esters) (provides complex examples)
c. http://www.acdlabs.com/iupac/nomenclature
Developed by Advanced Chemistry Development Laboratories
Recommendations 1993
R-5 Applications to Specific Classes of Compounds
R-5.7 Acids and Related Characteristic Groups
R-5.7.4 Salts and esters
R-5.7.4.2 Esters. (Gives detailed rules for nomenclature.)
3. Applications
a. Name the following:
O
O
O
O
b. Draw structural formulas for the following compounds:
3-bromobutyl propanoate
benzyl 3-nitrobenzoate
O
Cl
O
O
O
ethyl 2-hydroxy-4-methylpentanoate
2-methylcyclohexyl butanoate