Learning to be green: Involving students in the decision making process

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Learning to be green Involving students in the
decision making process

• Rich Gurney
• Department of Chemistry
• Simmons College
• Boston, MA 02115
• gurney_at_simmons.edu

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Success is a journey, not a destination. The
doing is often more important than the outcome.
- Arthur Ashe
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Four stages of greening a process

• choices
• of the reaction
• in performing the reaction
• in isolating and purifying the product
• in characterizing the outcome of the reaction

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Four stages of greening a process

• choices
• of the reaction
• in performing the reaction
• in isolating and purifying the product
• in characterizing the outcome of the reaction

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When choosing a synthetic path, consider...

• Safety
• Hazards
• Disposal
• Energy
• Solvents

• Applicability
• Selectivity
• Effectiveness
• Yield
• Time

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Route 1 Na2Cr2O7 / H2SO4 Route 2 NaOCl / HOAc

• Hazards of oxidants
• Na2Cr2O7
• Cr (VI)
• Highly carcinogenic (inhalation)
• Target kidney, liver, respiratory system,
• eye skin.
• Poison

NaOCl - Organochlorine formation - contains
traces Hg
Pavia, D. L. Lampman, G. M. Kriz, G. S. Engel,
R. G. Introduction to Organic Laboratory
Techniques, a Small Scale Approach Third
Edition Saunders College Publishing Fort Worth,
TX, 1999.
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Twelve Principles of Green Chemistry
How can we improve the process?

• 3. Process should use or generate little or no
  toxic materials.
• 5. Auxiliary substances should be eliminated
  whenever possible (solvents, separating agents)
  or be innocuous.
• 6. Energy requirements should be minimized.

• Solvent (5)
• Heterogeneous/Homogeneous (3 5)
• Microwave heat (6)
• Speed (6)

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Solvent vs Solvent-Free

• Short-term Health Effects
• dermatitis or skin problems (drying, cracking,
  reddening or blistering of the affected area)
• headaches
• drowsiness
• poor coordination
• nausea

• Long term Heath Effects
• the brain and the nervous system
• liver damage
• blood-forming system
• kidneys
• fertility of both M F
• carcinogenic (benzene)
• synergistic effects with other chemicals and
  drugs
• death

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Homogeneous vs Heterogeneous

• Heterogeneous
• easy and inexpensive removal
• safe to store, long life time
• wide range of utility
• non-toxic, Regenerable
• easy and safe disposal
• easy to handle
• increased stability
• avoids formation of inorganic salts

• Homogeneous
• difficult and expensive to separate from the
  reaction products and the solvent
• short life time
• short range of utility
• degrades easily
• not safe to dispose
• hard to handle

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Conventional Heating vs Microwave Energy
Glass Pressure Tube

• No boundary layer - Internal heating is maximized
  by direct heating mechanism
• No temperature gradient, homogenous heating
  optimizes purity of the reaction
• Heat source started and ceased instantaneously
• Shortened reaction times ? decrease energy
  requirement
• Superheating is possible, especially with
  pressure tube

Larhed M. Moberg C. Hallberg A.
Microwave-accelerated homogenous catalysis in
organic chemistry. Acc. Chem. Res. 2002, 35,
717 - 727.
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How can we improve the process?
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Standard Method Bleach (NaOCl)
Standard Method Sodium dichromate (Na2Cr2O7)
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Solvent-Free, Microwave, Oxidation ReactionsDr.
Rajender Varma, U.S. EPA

• Clayfen
• Clay-cop Hydrogen Peroxide
• Chromium Trioxide impregnated on wet Alumina
• Iodobenzene Diacetate on Alumina
• Activated Manganese Dioxide on Silica Gel

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Class A Poison causes muscle contractions
constricting airways and serious potentially
fatal lung damage causing delayed pulmonary edema
and a potentially time delayed immune system
attack on the lungs.
accidental or intentional swallowing of larger
amounts of CrO3 has caused stomach upsets and
ulcers, convulsions, kidney and liver damage, and
even death.
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Oxidation
Fall 2003 EXPERIMENTAL PROCEDURE Grind active
MnO2, silica gel, and borneol in a mortar and
pestle, until a homogenous mixture is obtained.
Transfer this sample into a capped glass
scintillation vial. Place in the center of a
household (65) microwave. Microwave at maximum
intensity for 100 s. Remove the hot vial
carefully. Follow the reaction, by TLC (CH2Cl2)
of a 1 mL diethyl ether extract of a spatula of
the reaction material. Repeat the microwave
heating as necessary. Once the reaction is
complete by TLC and the reaction material is
cooled to room temperature add 5 mL of CH2Cl2.
Separate the organic layer by vacuum filtration
and remove the solvent to obtain crude product.
Redissolve crude product in a minimum amount of
diethyl ether to transfer to a sublimation
chamber. Sublime product. Characterize final
product by TLC (CH2Cl2).
MnO2 - SiO2
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Four stages of greening a process

• choices
• of the reaction
• in performing the reaction
• in isolating and purifying the product
• in characterizing the outcome of the reaction

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• Fall 2003
• Can we find a better TLC solvent system to
  replace CH2Cl2?
• (101, hexaneEtOAc) works perfectly.
• Can the Et2O for TLC extract be replaced with a
  better solvent?
• hexanes - NO, EtOAc - no, EtOH - no, iPrOH -
  no.
• Can we eliminate the final extraction solvent
  (CH2Cl2 / Et2O)?
• place the glass vial in a heated sand bath,
  product camphor sublimes directly from the
  reaction mixture
• product collects in the cap.
• introduction of new heat source, hot plate /
  sand bath.
• Can a test-tube replace the glass vial for final
  sublimation?
• camphor sublimes toward the top of the tube,
  easier to collect
• product falls back onto the reaction
  materials.
• How long is too long? Can we heat the reaction
  for a longer period and obviate the need to
  follow the reaction?
• 20 sec, 40 sec, 60 sec, 120 sec, camphor to
  borneol ratio increasing.
• brown/white film climbing the side of the
  glass vial, top most rim of vessel
• white crystals form.
• white crystals are product!
• microwave oven can overheat.

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• Fall 2003
• Can we eliminate the separate sublimation step
  and thereby eliminate the energy required for
  heating the sand?
• upon further heating in the microwave, the
  camphor sublimes directly in the reaction vessel
  from the reaction mixture.
• yield low due to difficulty in isolating the
  product from the glass vial.
• Can a corked test-tube replace the glass vial?
• camphor sublimes toward the top of the tube,
  easier to collect
• product falls back onto the reaction
  materials.
• Can a Petri-Dish replace the corked test-tube?
• camphor sublimes on top dish, which is easily
  removed from the bottom, and product isolation
  is greatly facilitated.
• How green is the characterization of the final
  product? Is TLC the best method of analysis?
• IR Spectroscopy can be used to easily
  distinguish borneol from camphor,
• the final product is often contaminated with
  traces of water, which can be misinterpreted as
  an alcohol.

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Oxidation
Fall 2003 EXPERIMENTAL PROCEDURE Grind
active MnO2, silica gel, and borneol in a mortar
and pestle, until a homogenous mixture is
obtained. Transfer this sample into a capped
glass scintillation vial the bottom of a
Petri-dish. Replace Petri dish cover and place
in the center of a microwave. Microwave at
maximum intensity for 100 s. Remove the hot dish
carefully. Follow the reaction, by TLC (CH2Cl2)
of a 1 mL diethyl ether extract of a spatula of
the reaction material. Repeat the microwave
heating as necessary. Once the reaction is
complete by TLC and the reaction material is
cooled to room temperature add 5 mL of CH2Cl2.
Separate the organic layer by vacuum filtration
and remove the solvent to obtain crude product.
Redissolve crude product in a minimum amount of
diethyl ether to transfer to a sublimation
chamber. Sublime product. Recover the sublimed
camphor from the Petri-dish cover with a razor
blade. Characterize final product by TLC
(CH2Cl2). Characterize final product by IR
Spectroscopy.
MnO2 - SiO2
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MnO2 - SiO2
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MnO2 - SiO2
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Fall 2004 EXPERIMENTAL PROCEDURE Grind active
MnO2, silica gel, and borneol in a mortar and
pestle, until a homogenous mixture is obtained.
Transfer this sample into the bottom of a
Petri-dish. Replace Petri-Dish cover and place
in the center of a microwave. Microwave at
maximum intensity for 100 s. Remove the hot dish
carefully. Recover the sublimed camphor from
the Petri-dish cover with a razor blade.
Characterize final product by IR Spectroscopy.
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Fall 2004 Can we prevent the microwave from
overheating? a beaker of water absorbs excess
energy in the microwave. but increases the -OH
stretch in the IR spectrum of the product. Can we
prevent the microwave from overheating? a
beaker of alumina absorbs excess energy and does
not increase the water content in the camphor
product. Can we diminish the water signal in the
IR of the camphor product? drying the silica
gel and the MnO2 before use decreases water in
the camphor product. Can we maximize the yield
of camphor by placing an ice cold Erlenmeyer on
top of the Petri-dish cover? ice cold
Erlenmeyer does not appear to increase yield,
but increases the OH stretch in the IR spectrum
of the product. Can we maximize the yield of
camphor by using a Petri-dish with a smaller
thickness to decrease the distance between the
reaction medium and the product collection
vessel? decreasing the distance increases the
amount of MnO2 that is carried-up with the
sublimed camphor product. Can we increase the
purity of the sublimed camphor by increasing the
distance between the reaction medium and the
product collection vessel? increasing the
distance decreases the amount of MnO2 in the
product appears to increase the yield.
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Fall 2004 Can we decrease the amount of MnO2
that is carried-up with the sublimed camphor
product, by adding a thin layer of pure silica
gel over the reaction medium? sublimed
material slightly cleaner, yield
decreases. Can we minimize the amount of MnO2
that is carried-up with the sublimed camphor
product, by increasing the particle size? Can we
simply shake the reagents together instead of
grinding them? the sublimed material is
predominantly borneol instead of camphor when the
reagents are shaken together instead of
ground. Can we create a semi-continuous reaction
vessel by layering the MnO2-silica over the
borneol? no camphor is isolated. Can the same
reaction be used for the conversion of other
alcohols? norborneol can be converted to
norcamphor Does freshly prepared MnO2 work
better than store bought MnO2? MnO2 from
Aldrich behaves identically to freshly prepared
MnO2 Can we increase the yield of camphor by
spreading out the reaction medium on the bottom
Petri-dish? yield improves, yield decreases,
yield remained the same? Can we increase the
yield of camphor by piling the reaction medium in
the center of the Petri-dish? yield improves,
yield decreases, yield remained the same?
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Fall 2004 Is the reaction stoichiometric or
catalytic? If the reaction is catalytic, can the
reaction medium be used again to produce more
camphor if more borneol is added? If the reaction
is catalytic, can the catalyst be regenerated? If
the reaction is catalytic, how many times can the
reaction medium be reused? What is the optimal
heating time to produce camphor, while minimizing
the sublimation of the starting borneol? Does the
particle size of the silica gel matter? Can the
reaction product ratio be followed by GC/MS? Can
the reaction product ratio be determined by 1H
NMR? Why cant we cancel the rest of the
semester and continue working on this
experiment? Why havent we been introduced to
green chemistry earlier? Why isnt every lab a
green chemistry lab? Who in their right mind
thinks that green chemistry is a bad idea? Why
is this (Green Chemistry) a separate concept from
regular Chemistry?
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Fall 2005 A beaker of dry ice atop the Petri
Dishes, increases condensation of product by
cooling the surface without addition of
water. Reaction is not catalytic. Used
manganese dioxide silica mixture, can not be
reused. Many different reactor designs can be
used effectively. The particle size of the
silica gel does not cause a statistically
significant increase in yield or purity of
camphor. The reaction product ratio can be
followed by GC/MS using a standard GowMac GC
using temperature settings typically suited for
the separation of cyclohexane and toluene. The
presence of borneol in the camphor product down
to a 5 can be observed by 1H NMR (90 MHz, EFT
Anasazi). The yield of camphor can increase
from 12 - 15 to 85 - 92 while still maintaining
a 90 - 95 purity level by heating the reactor
directly on a hotplate, by carefully monitoring
the temperature. (Best temperature program
25oC to 165oC over 5 min. hold at 165oC for 10
min. ramp up to 200oC over 5 min. and hold at
200oC for 10 min.). Better reactor can be
designed for hotplate reaction.
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Alternative Jetsons Probe By Tayaba Naz 4
Watch Glass 1 Watch Glass Wide-mouth Powder
Glass Funnel Hotplate 0.350g MnO2 0.70g Silica
Gel 0.40g Borneol Step 1 Weigh the small watch
glass and the funnel. Step 2 Mix the reagents
in a small 50-mL beaker with a metal spatula for
5 minutes and pour the regents in a pile on the
large watch glass. Step 3 Cover the reagents
with the cut-off or wide-mouth powder funnel as
shown in the figure above. Place the small watch
glass on the mouth of the funnel. Step 4
Carefully put the setup on the hotplate and
gradually raise the temperature of the hotplate
to 165oC over 5 minutes. Monitor the
temperature with a thermocouple. Step 5 Hold the
temperature of the hotplate at 165oC for 10
minutes. Step 6 Gradually raise the temperature
of the hotplate to 200oC over 5 minutes and hold
the temperature of the hotplate at 200oC for 10
minutes. Step 7 Carefully remove the setup from
the hotplate and allow it to cool for about 5
minutes. Ensure the temperature is below
45oC Step 8 Weigh the funnel and the small watch
glass with the sublimed camphor product and
determine the isolated weight and percent yield
of your product. Step 9 Run TLC/IR/NMR/GC on
your product to check the purity.
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• Key Concepts introduced solid-phase green
  oxidation
• Synthesis Solid phase oxidation chemistry
• Work-up techniques heterogeneous extraction
• Purification techniques sublimation
• Characterization methods
• sealed capillary tube melting point
  determination
• thin layer chromatography (ethyl
  acetate/hexanes)
• Value Added solid-phase green oxidation
• Added Characterization methods due to extra time
  
• 1H NMR (CDCl3)
• GC (traces of diethyl ether)
• IR (KBr)
• Contextualized discussion of
• heterogeneous reactions
• solvent free reactions
• MSDS, safety, disposal, environmental
  consequences
• alternative energy sources (reaction can be done
  in microwave)
• choosing from multiple synthetic procedures

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• Unanticipated outcomes solid-phase green
  oxidation
• high level of student engagement with content
• high level of student personal accountability
• engagement within research and scientific method
• increased enthusiasm for chemistry and chemical
  research
• true concern and appreciate for disposal and
  safety
• every student became a critical evaluator
• every student became a contributing member of my
  research group

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We dont receive wisdom, we must discover it
ourselves after a journey that no one can take
for us, or spare us. Marcer Proust Who would
venture upon the journey of life, if compelled to
begin it at the end. Madame de Maintenon. Am
I going to be an author on the paper? Brandi
Watts, Simmons 05 Maybe I should consider a
career in chemical research instead of medical
school because I can bring about greater good, by
championing green chemistry. Tayaba Naz 08
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Acknowledgements

• Tayaba Naz, Simmons College (08)
• Shauna Tracy, Simmons College (08)
• YinYin Lin, Simmons College (05)
• Craig Schwartz, Northwestern University (04) (UC
  Berkeley)
• Marc Sala, Northwestern University (04)
  (Northwestern Medical)
• Students in CHEM 225, Fall 2003, 2004, 2005
• Henry and Camille Dreyfus Foundation Postdoctoral
  Fellowship in Environmental Chemistry
• Simmons College Faculty Start-Up Funds.

Procedures? Slides? Technical help? Questions?
Contact me Rich Gurney Department of
Chemistry Simmons College Boston, MA
02115 gurney_at_simmons.edu (617) 521 - 2729
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Procedures? Slides? Technical help? Questions?
Contact me Rich Gurney Department of
Chemistry Simmons College Boston, MA
02115 gurney_at_simmons.edu (617) 521 - 2729
34

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• www.ohsrep.org.au/hazards/solvents.html
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