2. Carbon carbon multiple bonds (double or triple) are not normally reduced by metal hydrides. State the reagents and conditions required to bring about reduction of each of the following: a) cyclohexene cyclohexane b) pent-2-yne → cis-pent-2-ene

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Chapter1: Chemical Foundations
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01:50
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4CH003/UM1: Fundamentals of...
Introduction
NaBH4
OH
C=0
H
benzophenone
diphenylmethanol
Ketones are readily reduced to secondary alcohols by reaction with sodium
borohydride. The aim of this experiment is to determine the time required to
effect
the complete conversion
of the ketone, benzophenone to
diphenylmethanol at room temperature. This investigation may be achieved
by isolating and analyzing the reaction product after different reduction times.
Infrared spectroscopy affords a convenient method of analysis; by comparing
the IR spectrum of the crude reaction product at different time intervals one
would expect to see the intensity of the hydroxyl absorption peak increase
relative to that of the original carbonyl peak. From this you can deduce the
optimum time for the reduction process at room temperature.
Procedure
Note the "reduction time" that the demonstrator assigns to your group.
Different groups will be assigned different times, eithert = 2.5 minutes, 10
minutes or 30 minutes.
Add benzophenone (1g, 0.005mol) and ethanol (10ml) into a 250ml conical
flask and swirl until it dissolves.
In a separate small beaker make a solution of sodium borohydride (250mg) in
water (2ml).
dissolution if required.
You may carefully warm this under a warm tap to help
Prepare a mixture of iced water (80ml) containing 2M hydrochloric acid (20ml)
in a 250ml beaker and store it on an ice bath.
Test that your stopwatch works and when ready add the sodium borohydride
solution in one go to the benzophenone solution in the conical flask.
Immediately start timing and when you get to your assigned time (x minutes)
quench the reaction by precipitating out the crude reaction product by addition
of the cold acidified water mixture. Transfer the contents of the conical flask
to a 250ml separating funnel and wash with an aliquot of diethyl ether (50ml).
Run off the aqueous layer into a clean beaker, and collect the organic ether
layer in a conical flask. Replace the aqueous
yer into the se
funnel
3
and re-extract with a second fresh aliquot of diethylether (50ml). Discard the
spent aqueous layer and combine the ether layer in the separating funnel.
Wash the ether layer with a fresh aliquot of distilled water (50ml), remove the
washing and transfer the organic layer into a clean 250ml conical flask. Dry
the organic layer over anhydrous magnesium or sodium sulphate. Filter off
the drying agent through a fluted filter paper and collect the filtrate directly in a
round bottomed flask (placed on a cork ring).
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Transcribed Image Text:01:50 4G File Details 4CH003/UM1: Fundamentals of... Introduction NaBH4 OH C=0 H benzophenone diphenylmethanol Ketones are readily reduced to secondary alcohols by reaction with sodium borohydride. The aim of this experiment is to determine the time required to effect the complete conversion of the ketone, benzophenone to diphenylmethanol at room temperature. This investigation may be achieved by isolating and analyzing the reaction product after different reduction times. Infrared spectroscopy affords a convenient method of analysis; by comparing the IR spectrum of the crude reaction product at different time intervals one would expect to see the intensity of the hydroxyl absorption peak increase relative to that of the original carbonyl peak. From this you can deduce the optimum time for the reduction process at room temperature. Procedure Note the "reduction time" that the demonstrator assigns to your group. Different groups will be assigned different times, eithert = 2.5 minutes, 10 minutes or 30 minutes. Add benzophenone (1g, 0.005mol) and ethanol (10ml) into a 250ml conical flask and swirl until it dissolves. In a separate small beaker make a solution of sodium borohydride (250mg) in water (2ml). dissolution if required. You may carefully warm this under a warm tap to help Prepare a mixture of iced water (80ml) containing 2M hydrochloric acid (20ml) in a 250ml beaker and store it on an ice bath. Test that your stopwatch works and when ready add the sodium borohydride solution in one go to the benzophenone solution in the conical flask. Immediately start timing and when you get to your assigned time (x minutes) quench the reaction by precipitating out the crude reaction product by addition of the cold acidified water mixture. Transfer the contents of the conical flask to a 250ml separating funnel and wash with an aliquot of diethyl ether (50ml). Run off the aqueous layer into a clean beaker, and collect the organic ether layer in a conical flask. Replace the aqueous yer into the se funnel 3 and re-extract with a second fresh aliquot of diethylether (50ml). Discard the spent aqueous layer and combine the ether layer in the separating funnel. Wash the ether layer with a fresh aliquot of distilled water (50ml), remove the washing and transfer the organic layer into a clean 250ml conical flask. Dry the organic layer over anhydrous magnesium or sodium sulphate. Filter off the drying agent through a fluted filter paper and collect the filtrate directly in a round bottomed flask (placed on a cork ring). 1 Previous Next 3 000 Dashboard Calendar То-do Notifications Inbox LO
01:50
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File Details
4CH003/UM1: Fundamentals of...
ne penzoprienone Solution
Immediately start timing and when you get to your assigned time (x minutes)
quench the reaction by precipitating out the crude reaction product by addition
of the cold acidified water mixture. Transfer the contents of the conical flask
Solution I One go to
the
Conica TiaSK.
to a 250ml separating funnel and wash with an aliquot of diethyl ether (50ml).
Run off the aqueous layer into a clean beaker, and collect the organic ether
layer in a conical flask. Replace the aqueous layer into the separating funnel
3
and re-extract with a second fresh aliquot of diethylether (50ml). Discard the
spent aqueous layer and combine the ether layer in the separating funnel.
Wash the ether layer with a fresh aliquot of distilled water (50ml), remove the
washing and transfer the organic layer into a clean 250ml conical flask. Dry
the organic layer over anhydrous magnesium or sodium sulphate. Filter off
the drying agent through a fluted filter paper and collect the filtrate directly in a
round bottomed flask (placed on a cork ring).
Remove the ether solvent by rotary evaporation under reduced pressure
(consult the demonstrator about this technique).
The groups need to record the IR spectra of the starting material and the
crude products from each of the different reduction times. Compare and
contrast the spectra and comment upon the optimum time needed to effect
reduction under the reaction conditions used.
Questions
Other metal hydrides may be used to reduce-CArDony Lompounds for
example lithium aluminium hydride, Draw the structure and state the
namo of te reaction producrs If this reargen-wre-ueea to reduce each
of the following.
b) ethyletnanoate
2. Carbon carbon multiple bonds (double or triple) are not normally
reduced by metal hydrides. State the reagents and conditions required
to bring about reduction of each of the following:
а)
cyclohexene
суyclohexane
b)
pent-2-yne
→ cis-pent-2-ene
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Transcribed Image Text:01:50 4G File Details 4CH003/UM1: Fundamentals of... ne penzoprienone Solution Immediately start timing and when you get to your assigned time (x minutes) quench the reaction by precipitating out the crude reaction product by addition of the cold acidified water mixture. Transfer the contents of the conical flask Solution I One go to the Conica TiaSK. to a 250ml separating funnel and wash with an aliquot of diethyl ether (50ml). Run off the aqueous layer into a clean beaker, and collect the organic ether layer in a conical flask. Replace the aqueous layer into the separating funnel 3 and re-extract with a second fresh aliquot of diethylether (50ml). Discard the spent aqueous layer and combine the ether layer in the separating funnel. Wash the ether layer with a fresh aliquot of distilled water (50ml), remove the washing and transfer the organic layer into a clean 250ml conical flask. Dry the organic layer over anhydrous magnesium or sodium sulphate. Filter off the drying agent through a fluted filter paper and collect the filtrate directly in a round bottomed flask (placed on a cork ring). Remove the ether solvent by rotary evaporation under reduced pressure (consult the demonstrator about this technique). The groups need to record the IR spectra of the starting material and the crude products from each of the different reduction times. Compare and contrast the spectra and comment upon the optimum time needed to effect reduction under the reaction conditions used. Questions Other metal hydrides may be used to reduce-CArDony Lompounds for example lithium aluminium hydride, Draw the structure and state the namo of te reaction producrs If this reargen-wre-ueea to reduce each of the following. b) ethyletnanoate 2. Carbon carbon multiple bonds (double or triple) are not normally reduced by metal hydrides. State the reagents and conditions required to bring about reduction of each of the following: а) cyclohexene суyclohexane b) pent-2-yne → cis-pent-2-ene 1 Previous Next 3 000 Dashboard Calendar То-do Notifications Inbox LO
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