Teaching Guided-Inquiry
Organic Chemistry Labs
Jerry Mohrig
Carleton College
Northfield, MN
Workshop Objectives
Summer 2005
• Provide the participants hands-on experience with
question-driven, guided-inquiry organic chemistry
projects and experiments.
• Allow the participants to evaluate what works well for
guided-inquiry experiments and what are the practical
constraints.
• Help the participants learn how to invigorate their
laboratory courses by using question-driven
experiments.
• Explore whether graduate-student teaching assistants
can provide competent supervision in the use of
guided-inquiry organic chemistry labs and what
training will be necessary to do this successfully.
• Encourage sharing of positive and negative
experiences by participants regarding their teaching of
organic chemistry labs.
Two Important Questions
Why Do We Teach Labs?
What Are Our Goals In
Teaching Organic Chemistry Labs?
The Traditional Teaching Goals
• Help students to experience the material
taught in our lectures and deepen their
understanding of it
• Allow students to verify what the lab manual
says
• Teach students how to follow experimental
directions
Higher-Order Traditional Goals
• Teach modern laboratory techniques to
students
• Teach students to synthesize organic
compounds
The Important
“Non-Traditional Goals”
of Laboratory Teaching
• Teach students how to interpret experimental
results and draw reasonable conclusions
• Teach students how to design and carry out
experimental procedures
• Encourage students to ask questions and find
answers
• Allow students to explore the process of science
Styles of Lab Teaching
Traditional or Verification Experiments
Cookbook
Confirmation of knowledge students already have
Cosmic futility – make a white powder, prove it’s what you expect, and
donate it to chemical waste, again, and again, and again
Guided-Inquiry or Discovery Experiments/Projects
Question or purpose driven
Outcome not known but the chemistry builds on what the students know
A procedure is given
The experimental results must be evaluated and conclusions drawn
Open-ended Inquiry Experiments/Projects
Undetermined outcome
Students generate their own procedure
Research-like Projects
The Advantages of Multi-Week
Projects
•
•
•
•
Promote student engagement
Allow flexible use of lab time
Promote guided-inquiry instruction
Use organic synthesis in the context of
asking questions
• Provide good teamwork opportunities
• Effective at every level
• Allow lower lab costs
Traditional Grignard
Synthesis Project
NaBr
H2SO4/H2O
OH
H3C
reflux
SN 2
H3C
Br
H3C
Br
Mg
Br
H3C
ether
O
H3C
H2O, H+
OH
C4H9
H3C
CH2CH3
CH2CH3
Guided-Inquiry Grignard Project
Purpose: To design and carry out the Grignard synthesis of a secondary or
tertiary alcohol from a simpler primary alcohol
NaBr
H2SO4/H2O
R
Mg
OH
R = C3H7, C4H9, C5H11,
(CH3)2CHCH2CH2
reflux
SN 2
R
Br
R
MgBr
extraction, distillation ether
NMR or IR
O
OH
R'
R
R"
MgBr
R' = CH3, CH2CH3
R'' = H, CH3, CH2CH3
H2O, H+
R
R'
R''
characterization by
boiling point, GC and IR
Traditional Acetylation of
Ferrocene
O
C
CH3CO2COCH3
Fe
Fe
H3PO4
ferrocene
acetylferrocene
Guided-Inquiry Diacetylation of Ferrocene
Question: Which diacetylferrocene isomers form?
O
C
CH3COCl
Fe
Fe
AlCl3, CH2Cl2
ferrocene
acetylferrocene
O
O
O
C
Fe
O
O
O
C
C
C
C
or
Fe
or
Fe
C
1,1'-diacetylferrocene
mp 127
1,3-diacetylferrocene
mp 188
1,2-diacetylferrocene
mp 97
Keys to Success
in Using
Guided-Inquiry Labs
Teaching the Art of Data Interpretation
• Communication of the lab goals by the teacher
• A clear well-defined question or purpose, stated up front
• The right background material so that students can
successfully interpret their experimental data
• The availability of some modern instrumentation
• 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
• A range of question- and purpose-driven experiments and
projects, from the straightforward to the more sophisticated
• Teamwork opportunities
Summary
Guided-inquiry experiments and projects are
effective
• For teaching students how to evaluate their
experimental data and draw conclusions from them
• For helping students to learn how to design and
carry out experimental procedures
• For allowing students to experience first-hand the
science of organic chemistry