preparation of stilbenediol acetonide
DESCRIPTION
Organic multi-step synethesis of stilbenediol acetonideTRANSCRIPT
Preparation of Stilbenediol Acetonide
(1,2-dimethyl-1,5-dioxolane)
Abstract
In the preparation of stilbenediol acetonide, the first step was the synthesis of hydrobenzoin (1,2-diphenylethane-1,2-diol) by the reduction of benzil (dissolved in ethanol) with sodium borohydride, then heating the solution and adding water. The product crystallized in the reaction mixture, was washed with cold water twice to purify and isolated by filtration. The second step was reacting hydrobenzoin with acetone (reactant and a solvent) and iron (III) chloride (Lewis acid and catalyst), then heating the solution to synthesize cyclic stilbenediol acetonide. The solution was poured over water containing 3M potassium carbonate (a base) to react with the acid; the product was then extracted with methylene chloride, dried and evaporated to give stilbenediol acetonide. It was recrystallized in hexane to purify. Verification for both products included Infrared Spectroscopy, H NMR, and melting-point determination. We determined, from analyses, that we made the correct products.
Balanced Equations for Synthesis
Preparation of Hydrobenzoin from Benzil
Preparation of Stilbenediol Acetonide from Hydrobenzoin
OO OH
OH
NaBH4
OHOH
CH3 CH3
O
CH
CH
O O
CH3CH3
FeCl3
+
+ H2O
Procedures
Preparation of Hydrobenzoin
• Add .5g of dry benzil to a 50-ml flask• Add 5ml of 95% ethanol• Swirl contents to dissolve• Cook the solution in an ice bath until a fine
suspension appears • Add .1g NaBH4 to flask and swirl contents
for two to three minutes• Let the flask sit for 10 minutes with periodic
stirring• Add 5ml of water; heat the flask until
solution boils• Add 10ml water and allow to cool to room
temperature• Vacuum dry the crystals; wash several
times (with cold water) and dry the crystals• Transfer product to a watch glass and allow
to dry completely
Preparation of Stilbenediol Acetonide
• Dissolve .3g of hydrobenzoin in 9ml acetone• Add .1g FeCl3• Reflux the mixture for 20 minutes using an
esterification apparatus• Transfer the mixture to a flask containing
12ml water (more water may be added) and 3ml 3M potassium carbonate solution
• Extract the product with at least 9ml methylene chloride
• Wash extract with 7.5ml of water; dry the solution over anhydrous calcium chloride and evaporate dry (or dry under vacuum)
• Dissolve crude product in .9-1.5ml hexane; cool in ice and vacuum dry the product
DataCompound Molecular
WeightDensity Melting
Point Boiling Point
Solubility
(in H2O)
Benzil 210.23 g/mol 1.23g/cm3 94.5-95.08°C
346-348 °C Insoluble
Sodium Borohydride
37.83 g/mol 1.07 g cm-3 400 °C (decomposes)
500 °C Soluble
Hydrobenzoin 214.25 g/mol N/A 137°C N/A Slightly
Soluble
Acetone 58.08 g/mol .79 g/cm³ −94.9 °C 56.53 °C Miscible
Stilbenediol
Acetonide
254.3 g/mol N/A 147°C N/A N/A
Benzil to Hydrobenzoin(.5g benzil)(1 mol benzil/210.23 g benzil)(1 mol hydrobenzoin/1 mol benzil)(214.25g hydrobenzoin/1 mol hydrobenzoin)(1000mg/1g)= 527.9mg hydrobenzoin
Hydrobenzoin to Stilbenediol Acetonide(300mg hydrobenzoin)(1g/1000mg)(1 mol hydrobenzoin/214.25 g hydrobenzoin)(1 mol stilbenediol acetonide/1 mol hydrobenzoin)(254.3g stilbenediol acetonide/1 mol stilbenediol acetonide)(1000mg/1g)= 356.1 mg stilbenediol acetonide
Calculations for Starting MaterialTo get 300mg final product
Melting Point Data and Calculations
Hydrobenzoin
• Melting point
- Expected: 137°C
- Experimental 130-131°C
• Percent Yield - Theoretical Yield
(.5g benzil)(1 mol benzil/210.23 g benzil)(1 mol hydrobenzoin/1 mol benzil)(214.25g hydrobenzoin/1 mol hydrobenzoin)(1000mg/1g)= 527.9mg hydrobenzoin
- Actual Yield
-Crude Product:
.411g actual/.5279g theoretical= 78% crude
- Pure Product
.359g actual/.5279g theoretical=68% pure
Stilbenediol Acetonide
• Melting point - Expected: 147°C
- Experimental:140°C
• Percent Yield - Theoretical Yield
(300mg hydrobenzoin)(1g/1000mg)(1 mol hydrobenzoin/214.25 g hydrobenzoin)(1 mol stilbenediol acetonide/1 mol hydrobenzoin)(254.3g stilbenediol acetonide/1 mol stilbenediol acetonide)(1000mg/1g)= 356.1 mg stilbenediol acetonide
- Actual Yield
-Crude Product:
.321g actual/.3561g theoretical= 90% crude
- Pure Product
.289g actual/.3561g theoretical=81% pure
OHOH
Functional Group Class ExpectedBand Positions and Intensities of
Absorption
ExperimentalEquivalents
O-H 3200-3650 cm-1 (broad) 3369 cm-1, 3312 cm-1
Benzene/Aromatics 3030 cm-1, 1660-2000 cm-1 (both weak) and 1450-1600 cm-1 (medium)
3056 cm-1 , 1449 cm-1, 1494 cm-1, 1578 cm-1, 1591 cm-1
C-O 1050-1150 cm-1 (strong) 1173 cm-1
OHOH
Type of Hydrogen Expected Chemical Shift Experimental Equivalents
Aromatic 6.5-8 ppm 7.2 ppm
Alcohol (OH) 2.5-5 ppm(variable)
3.3 ppm
Alcohol (HO-CH)
3.3-5 ppm 4.6, 5.2 ppm
CH
CH
O O
CH3CH3
Functional Group Class ExpectedBand Positions and Intensities of
Absorption
ExperimentalEquivalents
Benzene/Aromatics 3030 cm-1, 1660-2000 cm-1 (both weak) and 1450-1600 cm-1
(medium)
3028 cm-1, 2999 cm-1, 1496 cm-1, 1453 cm-1
C-O 1050-1150 cm-1 (strong) 1046 cm-1, 1080 cm-1, 1153 cm-1
CH
CH
O O
CH3CH3
Type of Hydrogen Expected Chemical Shift Experimental Equivalents
Aromatic 6.5-8 ppm 7-8 ppm
Ether (CO-CH)
3.3-5 ppm 3-3.5 ppm
Methyl .7-2.7 2.5 ppm
Conclusions• Our experiment was the two-phase sythesis of stilbenediol acetonide. The first
phase involved the reduction of benzil (in ethanol) with sodium borohydride, then heating the solution and adding water to produce hydrobenzoin. After purification and drying, we determined our crude yield to be 78% and our pure yield to be 68%. Verification included IR spectroscopy, H NMR, and melting point analysis. We concluded that our product was pure through the closeness of the expected and experimental melting points, and what was expected and obtained in our spectral analyses.
• The second phase involved the synthesis of stilbenediol acetonide from our hydrobenzoin, by reacting it with acetone (both a reactant and solvent), and adding the acid catalyst iron (III) chloride. The solution was poured into water and potassium carbonate (a base) to react with the acid; the product was then extracted with methylene chloride. After purification and drying, we determined our crude yield to be 90% and our pure yield to be 81%. Verification included IR spectroscopy, H NMR, and melting point analysis. We concluded that our product was pure through the closeness of the expected and experimental melting points, and what was expected and obtained in our spectral analyses.