Draw the structure of the meso diol and of its corresponding acetonide.

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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Draw the structure of the meso diol and of its corresponding acetonide.

Procedure
This experiment should give a very high yicld of the product (>90%) providing you are careful to
ensure that transfers are complete by using diethyl ether.
1. Dissolve 250 mg of the diol in 5.0 mL of 2,2-dimethoxypropane in a 25 mL round bottom flask.
Then add 0.011 g of p-toluenesulfonic acid, 0.30 g of anhydrous MgSO4 and a Teflon boiling
chip.
2. Equip the flask with a condenser and a heating mantle, bring the reaction to reflux. After 20-25
minutes, remove the heat source and allow the flask to cool to room temperature.
3. Transfer the reaction mixture to a separatory funnel by carefully decanting the supernatant liquid
from the solid residue in the bottom of the flask. Use small portions of diethyl ether to wash the
residue and decant the organic rinsings into the separatory funnel so that a total volume of 5 mL
of ether has been used.
4. Wash the organic material with saturated sodium bicarbonate solution (5 mL) and water (2 x 5
mL) followed by saturated sodium chloride solution (5 mL).
5. Transfer the organic phase to a 25 mL Erlenmeyer flask. Use several portions of ether (~5 mL
total volume) to rinse the separatory funnel. These rinsings are then added to the Erlenmeyer
flask.
6. Dry the organic solution with anhydrous sodium sulfate.
7. Carefully pipet the organic liquid into a clean, tared 50 mL round bottom flask. Again, use a
small amount of ether to wash the sodium sulfate and transfer these washings to the flask.
8. Concentrate the solution by rotary evaporation. Once the ether has been removed, increase the
bath temperature to 60-70°C to remove excess 2,2-dimethoxypropane. After the solvent has been
completely removed, the acetonide should crystallize.
9. Take the melting point of the product. Obtain an 'H NMR spectrum of the product and determine
whether the starting hydrobenzoin was meso or racemic. Take an IR of your product. Place the
remainder of your product in a vial and label it with your name, section, product name, and amount
in grams.
Transcribed Image Text:Procedure This experiment should give a very high yicld of the product (>90%) providing you are careful to ensure that transfers are complete by using diethyl ether. 1. Dissolve 250 mg of the diol in 5.0 mL of 2,2-dimethoxypropane in a 25 mL round bottom flask. Then add 0.011 g of p-toluenesulfonic acid, 0.30 g of anhydrous MgSO4 and a Teflon boiling chip. 2. Equip the flask with a condenser and a heating mantle, bring the reaction to reflux. After 20-25 minutes, remove the heat source and allow the flask to cool to room temperature. 3. Transfer the reaction mixture to a separatory funnel by carefully decanting the supernatant liquid from the solid residue in the bottom of the flask. Use small portions of diethyl ether to wash the residue and decant the organic rinsings into the separatory funnel so that a total volume of 5 mL of ether has been used. 4. Wash the organic material with saturated sodium bicarbonate solution (5 mL) and water (2 x 5 mL) followed by saturated sodium chloride solution (5 mL). 5. Transfer the organic phase to a 25 mL Erlenmeyer flask. Use several portions of ether (~5 mL total volume) to rinse the separatory funnel. These rinsings are then added to the Erlenmeyer flask. 6. Dry the organic solution with anhydrous sodium sulfate. 7. Carefully pipet the organic liquid into a clean, tared 50 mL round bottom flask. Again, use a small amount of ether to wash the sodium sulfate and transfer these washings to the flask. 8. Concentrate the solution by rotary evaporation. Once the ether has been removed, increase the bath temperature to 60-70°C to remove excess 2,2-dimethoxypropane. After the solvent has been completely removed, the acetonide should crystallize. 9. Take the melting point of the product. Obtain an 'H NMR spectrum of the product and determine whether the starting hydrobenzoin was meso or racemic. Take an IR of your product. Place the remainder of your product in a vial and label it with your name, section, product name, and amount in grams.
Formation of Acetals, the Acetonide of Hydrobenzoin
Background
The object of the present experiment is to demonstrate, using logic based on nuclear magnetic
resonance (NMR) spectral data, whether the hydrobenzoin you start with is the meso or the racemic
isomer.
The 1,2-diphenyl-1,2-ethanediol (hydrobenzoin) is reacted with acetone to form a crystalline
acetonide (a ketal) that will have either structure 1 or 2. Examination of the NMR spectrum of this
derivative will reveal whether the two methyl groups of the acetonide are equivalent or not and thus
whether the diol was meso or racemic.
CH3
CH
Ph
PhIl
PhIll
1
2.
Reaction:
Но
OH
H.
H-
H-
OH
(no stereochemistry
implied)
(cat.)
Transcribed Image Text:Formation of Acetals, the Acetonide of Hydrobenzoin Background The object of the present experiment is to demonstrate, using logic based on nuclear magnetic resonance (NMR) spectral data, whether the hydrobenzoin you start with is the meso or the racemic isomer. The 1,2-diphenyl-1,2-ethanediol (hydrobenzoin) is reacted with acetone to form a crystalline acetonide (a ketal) that will have either structure 1 or 2. Examination of the NMR spectrum of this derivative will reveal whether the two methyl groups of the acetonide are equivalent or not and thus whether the diol was meso or racemic. CH3 CH Ph PhIl PhIll 1 2. Reaction: Но OH H. H- H- OH (no stereochemistry implied) (cat.)
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