Transcript ChemDraw - University of California, Irvine

Teaching Inquiry-Driven
Organic Chemistry Labs
Jerry Mohrig
Carleton College
Northfield, MN
Introduction and
Workshop Objectives
Summer 2007
Workshop Objectives
• Provide the participant hands-on experience with question-driven,
guided-inquiry organic chemistry projects and experiments.
• Allow the participant to evaluate what works well for guidedinquiry and design-based experiments and what are the practical
constraints.
• Help the participants learn how to invigorate their laboratory
courses by using inquiry-driven experiments and projects.
• Provide the participant experience with recasting a traditional
experiment or project into a question-driven or design-based one.
• Encourage sharing of positive and negative experiences by
participants regarding their teaching of organic chemistry labs.
• Explore whether graduate-student teaching assistants can provide
competent supervision in the use of inquiry-driven organic
chemistry labs and what training will be necessary to do this
successfully.
Why Do We Teach
Organic Chemistry Labs?
What Are Our Goals?
Traditional Lab Teaching Goals
•
Teach students how to follow experimental
directions
1) to verify what the lab manual says
2) to synthesize organic compounds
•
Teach modern laboratory techniques to students
•
Help students experience the material taught in
our lectures and deepen their understanding of it
The Important Non-Traditional Goals
of Laboratory Teaching
• Teach students how to interpret experimental
data and draw reasonable conclusions
from them
• Teach students how to design and carry out
experimental procedures
• Encourage students to ask questions and
find answers
• Allow students to experience first-hand the
science of organic chemistry
Styles of Lab Teaching
Traditional
Verification Experiments
Provide confirmation of knowledge that students have been asked to learn
Make a white powder, prove it’s what you expect, and donate it to chemical
waste, again and again – giving the word “cookbook” a bad name
Inquiry Driven
Guided-Inquiry or Discovery Experiments/Projects
Question driven
Outcome not known but the chemistry builds on what the students have
studied - experimental results must be evaluated and conclusions drawn
A procedure is often given
Design-Based Experiments/Projects
Adapting generic procedures to synthesize target compounds
Students make decisions on the design of experimental procedures
Open-Ended Inquiry Experiments/Projects
Students generate their own procedures and investigate the outcomes
Traditional Grignard Synthesis Project
H2SO4/H2O
H3C
OH
NaBr
H3C
Br
H3C
MgBr
Mg
H3C
Br
ether
O
H3C
OH
C4H9
H3C
H2O, H+
CH2CH3
CH2CH3
Design-Based Grignard Project
Purpose: To design and carry out the Grignard synthesis of a secondary or
tertiary alcohol from a simpler primary alcohol
R
OH
H2SO4/H2O
NaBr
R
Br
Mg
ether
R
MgBr
R = C3H7, C4H9, C5H11,
(CH3)2CHCH2CH2
O
OH
R
R'
MgBr
R''
R' = CH3, CH2CH3
R'' = H, CH3, CH2CH3
H2O, H+
R
R'
R''
O
O
H
+
R1
R2
NaOH
_H O
2
O
R1
R2
Disubstituted Chalcone
The Chalcone Project
O
O
H
O
NaOH
+
H2O
R2 80o R1
R1
R1 = CH3, OCH3, Cl,
or C6H5CH2O
R2 = CH3, OCH3, or F
R2
Disubstituted Chalcone
O
R1
ammonium formate
Pd/C
Hydrogenation Product(s)
methanol
R2 reflux
Which functional groups are reduced in the catalytic hydrogenation reaction?
Chalcone Project Assessment
University of Florida, Gainesville — Tammy Davidson
Fall 2006 − 60 students and 4 graduate-student TAs
Spring 2007 − 550 students and 36 TAs
• Student feedback was overwhelmingly positive
• The project was seen as a real-world lab experience
• It provided effective learning of spectroscopic
interpretation
• Students felt that the post-lab discussion was quite
valuable when the students and the graduate-student TA
were adequately prepared and the TA was a good
moderator
• Student understanding depended on the quality of the
teaching
TA Training and Feedback
TA Training
• Reading and discussion of the guided-inquiry approach in
several meetings during the first week
• TAs asked to talk about their past lab teaching and learning
styles and to discuss teaching modifications to foster guided
inquiry
• Goals and teaching of each experiment discussed during
the semester
Feedback
• TA time in lab richer and more rewarding
• Students less pressured
• Faculty have gone from skeptical to receptive
Some Student Comments
• I learned:
how to analyze IR, NMR, and GC-MS simultaneously
to determine the actual product formed.
that A + B doesn’t always equal C, and that’s OK.
• I learned a lot from the post-lab discussion. I wish this was
possible for each experiment. During the lab sessions, we
were usually very busy trying to complete the experiment on
time. It was nice to have a day where we could reflect and
talk about what we learned.
• I truly learned how chemists fit together a puzzle of data to
make conclusions, and how hard it can be to do that. It was
an incredible critical thinking exercise.
The Chalcone Post-Lab Discussion
• After evaluating all of your data, each team will make a 10minute presentation with visual aids, summarizing the data
and your interpretation of it
• A maximum of two teams will work with a specific chalcone
• The discussion moderator will not give answers but instead
will probe to see if the interpretations are consistent with the
data
• In a lab course, student notebooks/reports are due after the
discussion. In the workshop, we will have a recap at the end
• The post-lab discussion
1) is an important part of student learning in
guided-inquiry projects
2) demonstrates the process of science
Necessary Background Materials
Suitable written background materials must provide:
•
A clear well-defined question or purpose, stated up front
•
A well-written techniques book, which contains modern
spectroscopy as well as traditional lab techniques
•
Clear, student-friendly experimental directions or models
for developing them
•
Background material so that students can successfully
interpret their experimental data
Keys to Success in Using
Inquiry-Driven Labs
Teaching the Art of Data Interpretation and
Experimental Design
• Communication of the goals and methods to all
concerned
• Positive faculty participation
• Appropriate TA training
• Providing time for pre- and post-lab discussions
• Availability of modern instrumentation
• Availability of suitable written background materials