Unit 7 lab pt 1

REDUCTION OF CAMPHOR
• Camphor (1,7,7-trimethylbicyclo-[2.2.1]-2-heptanone) belongs to a
diverse family of naturally occurring compounds, known as terpenes,
which have carbon skeletons composed of 5-carbon isoprene units.
• Optically active camphor is isolated from camphor trees found in Java,
Brazil, China, and Sumatra.
• Camphor has many practical and important uses.
• For example, camphor is used as a preservative in pharmaceuticals, in
cosmetics, and even in embalming fluids.
• Camphor has also been used as an anesthetic, as a mild antiseptic,
and as a cardiac stimulant.
• The reduction of ketones to 2 alcohols is an example of a functional
group transformation, i.e., a reaction that changes a group or groups
attached to a compound but leaves the carbon backbone unaltered.
• The reverse reaction, oxidation, converts 2 alcohols back to ketones.
O
R
Reduction
R’
Ketone
Oxidation
HO
R’
C
R
H
2o Alcohol
• Commonly used reducing agents include complex metal hydrides,
such as LiAlH4 (lithium aluminum hydride) and NaBH4 (sodium
borohydride).
• In this experiment, we will use sodium borohydride to reduce
camphor, an optically active, naturally occurring ketone which can
form two products, borneol or isoborneol.
• The products differ in the way in which the metal hydride reducing agent
delivers a hydride ion to the planar carbonyl group.
• Stereochemical demands of the substrate, in this case camphor, can direct
the addition of metal hydride to one of two faces of the carbonyl.
• Addition of hydride to the exo face of camphor forms borneol, the endo
product.
• Addition of hydride to the other face of camphor forms isoborneol, the
exo product.
• If much more of one product is formed, the reaction can be said to be
stereoselective.
• By determining which (if either) product is preferentially formed, it is
possible to determine if and how the stereochemical demands of camphor
are controlling the reduction reaction.
• Once the product(s) are isolated and identified, it becomes possible
to determine if the reduction was stereospecific by measuring the
optical rotation of the starting material and product(s).
• If the reduction was stereospecific, optically pure (+)- or (-)-camphor
should form only (+)- or (-)-borneol, or only (+)- or (-)-isoborneol, with
no loss of optical purity.
• In this experiment, you will start with either (+)- or (-)-camphor. (The
camphor to be used will be assigned by your instructor.)
• From the sign of the optical rotations of the starting camphor and of
the product(s), you can confirm the identity of the product(s) and
determine the stereoselectivity, by determining if one of the expected
products, borneol or isoborneol, is formed in greater amount.
Procedure
1. Place 0.0132 mole of camphor in a 50 mL round-bottom flask (RBF). Add 8 mL of methanol and cool the flask in ice in a 250 mL
beaker ice bath. While the flask is cooling, weigh 0.016 mole of NaBH4 in a vial and keep it covered. Crush any large lumps with a
spatula.
2.Add NaBH4 to the camphor solution in 3 portions with cooling, as described in steps a-c below.
3. Remove the flask from the ice bath, and add about 2 scoopula-tips full of NaBH4. Swirl the mixture for 5-6 minutes. Crush any solid
lumps that form with a thin, bent spatula. Whenever the bubbling becomes vigorous and/or the flask no longer feels cool, return it to
the ice bath. Continue to swirl and crush lumps.
4. After about 6 minutes, cool the flask in the ice bath again; repeat step a.
5. Repeat step b, adding the remaining NaBH4.
6. After about 5 minutes, let the solution warm to room temperature. Swirl it occasionally for another 10 minutes. Meanwhile, clamp
the flask to a ring stand with the flask in contact with a sand bath and equip it with a reflux condenser. (Cooling water tubing will not
be needed for this short reflux time.) When bubbling becomes slow, heat the solution to boiling, and reflux it for about 5 minutes.
7. Put about 30 mL of ice into a 125 mL Erlenmeyer flask, cool the reaction mixture for a minute or two, and pour it with stirring onto
the ice. Rinse the reaction flask twice with 2 mL portions of methanol, and add the washes to the reaction mixture.
8. Stir the mixture until the ice melts. Collect the solid by vacuum filtration. Rinse the Erlenmeyer flask twice with 2 mL portions of
ice-cold distilled water, to ensure the complete transfer of the product.
9. Wash the filtered solid with cold distilled water, and dry withvacuum.
10. Cover the Buchner funnel with a Kimwipe, store it in a beaker until next week.
Week 2
• 1. Weigh your dry product.
• 2. Calculate the percent yield of product.
Reduction of Camphor
PRE-LAB
1. Please complete Sodium Borohydride Reduction OWL assignment online.
2. Please read Chapter 26: Sodium Borohydride Reduction of 2-methyl cyclohexanone in
Macroscale and Microscale Organic Experiments, 7th Edition, lab textbook.
3. Please watch the following video

OBJECTIVES
After completing this section, you should be able to
1. Write an equation to represent a typical reduction reaction.
2. Draw the structure of the product formed when a ketone reacts with sodium borohydride
in a reduction reaction.
3. Identify the reactants required to prepare a given compound by a reduction reaction.
4. Explain the general mechanism of the reduction reaction, without necessarily being able
to describe it in detail.
KEY TERMS
Make certain that you can define, and use in context, the key terms below.
•
Reduction reaction
STUDY NOTES
Camphor (1,7,7-trimethylbicyclo-[2.2.1]-2-heptanone) belongs to a diverse family of
naturally occurring compounds, known as terpenes, which have carbon skeletons composed of
5-carbon isoprene units. Optically active camphor is isolated from camphor trees found in Java,
Brazil, China, and Sumatra.
Camphor has many practical and important uses. For example, camphor is used as a
preservative in pharmaceuticals, in cosmetics, and even in embalming fluids. Camphor has also
been used as an anesthetic, as a mild antiseptic, and as a cardiac stimulant.
The reduction of ketones to 2 alcohols is an example of a functional group
transformation, i.e., a reaction that changes a group or groups attached to a compound but leaves
the carbon backbone unaltered. The reverse reaction, oxidation, converts 2 alcohols back to
ketones.
O
R
Reduction
R’
HO
Oxidation
Ketone
R’
C
R
H
2o Alcohol
Commonly used reducing agents include complex metal hydrides, such as LiAlH4 (lithium
aluminum hydride) and NaBH4 (sodium borohydride). In this experiment, we will use sodium
borohydride to reduce camphor, an optically active, naturally occurring ketone which can form
two products, borneol or isoborneol.
The products differ in the way in which the metal hydride reducing agent delivers a
hydride ion to the planar carbonyl group. Stereochemical demands of the substrate, in this case
camphor, can direct the addition of metal hydride to one of two faces of the carbonyl. Addition
of hydride to the exo face of camphor forms borneol, the endo product. Addition of hydride to
the other face of camphor forms isoborneol, the exo product. If much more of one product is
formed, the reaction can be said to be stereoselective. By determining which (if either) product is
preferentially formed, it is possible to determine if and how the stereochemical demands of
camphor are controlling the reduction reaction.
Once the product(s) are isolated and identified, it becomes possible to determine if the
reduction was stereospecific by measuring the optical rotation of the starting material and
product(s). If the reduction was stereospecific, optically pure (+)- or (-)-camphor should form
only (+)- or (-)-borneol, or only (+)- or (-)-isoborneol, with no loss of optical purity.
LAB REPORT
Procedure
1. Place 0.0132 mole of camphor in a 50 mL round-bottom flask (RBF). Add 8 mL of methanol
and cool the flask in ice in a 250 mL beaker ice bath. While the flask is cooling, weigh 0.016
mole of NaBH4 in a vial and keep it covered. Crush any large lumps with a spatula.
2. Add NaBH4 to the camphor solution in 3 portions with cooling, as described in steps a-c
below.
a. Remove the flask from the ice bath, and add about 2 scoopula-tips full of NaBH4. Swirl
the mixture for 5-6 minutes. Crush any solid lumps that form with a thin, bent spatula.
Whenever the bubbling becomes vigorous and/or the flask no longer feels cool, return it
to the ice bath. Continue to swirl and crush lumps.
b. After about 6 minutes, cool the flask in the ice bath again; repeat step a.
c. Repeat step b, adding the remaining NaBH4.
3. After about 5 minutes, let the solution warm to room temperature. Swirl it occasionally for
another 10 minutes. Meanwhile, clamp the flask to a ring stand with the flask in contact with
a sand bath and equip it with a reflux condenser. (Cooling water tubing will not be needed for
this short reflux time.) When bubbling becomes slow, heat the solution to boiling, and reflux
it for about 5 minutes.
4. Put about 30 mL of ice into a 125 mL Erlenmeyer flask, cool the reaction mixture for a
minute or two, and pour it with stirring onto the ice. Rinse the reaction flask twice with 2 mL
portions of methanol, and add the washes to the reaction mixture.
5. Stir the mixture until the ice melts. Collect the solid by vacuum filtration. Rinse the
Erlenmeyer flask twice with 2 mL portions of ice-cold distilled water, to ensure the complete
transfer of the product.
6. Wash the filtered solid with cold distilled water, and dry with vacuum.
7. Cover the Buchner funnel with a Kimwipe, store it in a beaker until next week.
8. Weigh your dry product.
Calculations:
1) The mass of the final product is 1.1g.
A) Calculate percent yield.
Post-Lab questions:
1. In the IR spectrum of the product, isoborneol, what is the approximate frequency of the
most important peak in the starting material that should be absent in the product?
2. Predict the major product in the reduction of camphor experiment.
Isoborneol IR spectrum