Chemistry 211
Fall 2010
Equilibrium Controlled Reactions:
Acid Base Reactions & Energy Relationships - 4
Table B
Conjugate Acid
CH4
:
: :
:
NH2
NH
~35
O
:
:O
:
~27
CH3
20
C
O
: :
:
CH3
OH
: OH
10
:O
:
H
16
15.7
O:
A. Exploration:
1. Compare the structures below and determine the variables from one structure to another.
NH2
NH
CH3 C
-
O:
: :
CH3
CH3
-
H
: :
C
C CH2
NH2
16
:O
:
CH3 C
H2O
: O:
:O :
CH3
-
CH3 C
O:
: :
CH3
:O
:
pKa
: :
CH2
CH3
OH
: :
~36
CH3
:
:
:
: :
NH2 -
NH -
: :
:
NH3
~40
~37
CH3
NH2
Conjugate Base
~42
: :
:
CH3
CH2: CH3
:
CH3
Conjugate Acid
: :
CH3
pKa
: :
CH3
Conjugate Base
4.8
Acid-Base Rxns & Energy Relationships-4
2
3
Acid-Base Rxns & Energy Relationships-4
2. Use the data in Table B to list the compounds in 1. in the order of decreasing acidity and provide a warrant supporting your claim citing
specific data in Table B. (As usual, more data supporting a warrant makes the claim stronger.)
Most Acidic
Middle
Least acidic
Warrant:
3. Which of the following ions has the lowest energy? Which has the highest energy? Provide a warrant supporting your claims and citing
specific data in Table B. (As usual, more data supporting a warrant makes the claim stronger.)
O
Lowest Energy
NH
C
CH2
:
O:
C
: :
-
: :
C
O
O
Highest Energy
Warrant:
B. Suggest theoretical backing to explain the effects observed above in terms of electron nuclear attraction and/or electron-electron repulsion.
Acid-Base Rxns & Energy Relationships-4
4
5
Acid-Base Rxns & Energy Relationships-4
C. Using the theoretical backing developed in Part B, select the most acidic proton(s) in the following compound. Then provide a warrant
describing the process and logic that led to your claim.
H H
H
H
C C
H
H
C
H N C
O
C
C
H
H
H
H H
H
Reflector’s Report Discussion:
Identify the most important concepts you learned from this activity:
What questions remain?
Strategy Analyst’s Report Discussion:
A. Exploration:
What role did question 1 play in the exploration of Table B in question 2?
What Principle or Assumption that wasn’t necessary for question 2 was required to answer question 3?
B. Theoretical Backing:
Acid-Base Rxns & Energy Relationships-4
6
What fundamental aspect of the variable identified in question A. 1. was the key to providing the backing needed in B.? How was it used?
Out of Class Applications for Acid Base Reactions &Energy Relationships - 4
A.
Reading Assignment: in CGWW: pp. 181-191.
B.
Activities:
1. CGWW has a subtitle “An acid’s pKa depends on the stability of its conjugate base.” (p. 187) We described acidity in terms of the energy
of the conjugate base. In this context, what is the relationship between a base’s energy and its stability? Provide a warrant to support your
claim.
2. Problem 4, in CGWW, CH 8: p. 207, first 2 molecules.
:
: :
3. For each of the following compounds, use the theoretical backing developed in this activity to select the most acidic proton(s):
H H
H H H H
H N C C O H
H
H
H C N C O C H
H C
C
H
H
C
H
H
H
H H
Then provide a warrant describing the process and logic that you used to reach your conclusions.
: :
:
4.
Which of the following ions should have the lower energy.
-
-
: :
CH2
: :
CH2
P H
S:
CH3
CH2
CH2
Provide a warrant describing how you used the theoretical backing developed in this activity to devise your claim.
CH3
7
For each of the following acid-base reactions, use the theoretical backing in this activity to predict whether the equilibrium constant
should be > or < 1. Provide a warrant describing the process and logic that you used to reach your conclusions.
a.
:
O
: :
b.
CH2 :
O: -
H
6.
:
+
:
+
NH2
:
:
+
:
NH
H +
CH3
O -
: :
:
:
5.
Acid-Base Rxns & Energy Relationships-4
O
H
H
For the following pair of equilibrium controlled reactions, predict which one should produce more product at equilibrium. Explain your
choice on the basis of the theoretical backing developed in this activity.
-S
O
+
+
O
S
-S
NH
-
-
HN
S
Acid-Base Rxns & Energy Relationships-4
8
C. Nomenclature of Ethers
1. CGWW: Ch. 2 p. 32
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 Ethers
Provides questions with answers
b. http://www.molecularmodels.ca/nomenclature/index-2.htm
Developed by Professor Dave Woodcock,
Sections:
Okanagan University College, British Columbia,
3. Functional Groups with Prefixes Only.
Canada
II. Alkoxyalkanes (Ethers). Click to reveal examples of naming
ethers.
(Contains many examples.)
Note: Your browser must have Java installed.
If you have problems, go to the top of the page at
http://www.molecularmodels.ca/nomenclature/index-2.htm and follow directions to manipulate structure and if necessary
download JAVA. If you have problems contact me.
c. http://www.acdlabs.com/iupac/nomenclature
Developed by Advanced Chemistry Development
Laboratories
(Gives detailed rules for nomenclature.)
Recommendations 1993
R-5 Applications to Specific Classes of Compounds
R-5.5 Hydroxy Compounds, their Derivatives and Analogues
R-5.5.4 Ethers and chalcogen analogues (consider only
ethers)
R-5.5.4.1 Substitutive names
R-5.5.4.2 Functional class names
3. Applications
a. Name the following:
O
O
O
Cl
b. Draw structural formulas for the following compounds:
Br
O
9
Acid-Base Rxns & Energy Relationships-4
Propyl cyclopentyl ether
2,5-dimethoxyhexane
1-bromo-1-propoxycycloheptane
dicyclobutyl ether