Benzil Reduction
Benzil Reduction
Introduction
The objective of the experiment was to reduce Benzil, using sodium borohyride as the reducing agent. In a benzil reduction, there are five possible products than can occur, specifically a racemic mixture of benzoin, racemic mixture of hydrobenzoin, or meso-hydrobenzoin. Therefore, three different tests were conducted in determining the identity of the product: melting point, thin light chromatography, and infrared spectroscopy. (a) Mechanism and reaction equation of benzyl reduction
Stereochemistry plays a vital role in the five possible products of benzil reduction. The five possible products in the reduction of benzil are due to the two carbonyl groups in benzil. If the sodium borohydride reduced only one carbonyl, then the product would be a racemic mixture of benzoin (R,S-). However, if both carbonyl groups are reduced, the possible products will be meso-hydrobenzoin (R,S-) in which the R enantiomers react to create an S chiral center and S enantiomers react to create an R chiral center or the R enantiomers react to create another R chiral center and S enantiomers react to create another S chiral center.
Key experimental details, observations and results Table 1. Amount of Reagent Used | Reagent | | Amount (mL or g) | Benzil | | 1.05g | | Sodium Borohydride | 0.20g | | Ethanol | | 10mL | |
1. Observations: a. When heating mixture of benzil and ethanol, dissolved and became yellow. b. Recrystallization occurred during NaBH4, appeared as small, white foaming bubbles c. Boiled-cloudy yellow color d. Cooling: had a pale yellow clear and white crystals started to appear 2. Description of product: e. Color: white f. Appearance: uniform, shiny, paper-like texture
Results Table 2. Experimental and Literature Melting Points | | | | | Name | | Experimental | | Name | | | Literature | Product | | 132.1 - 134.2°C | | Racemic Benzoin | |
Introduction
The objective of the experiment was to reduce Benzil, using sodium borohyride as the reducing agent. In a benzil reduction, there are five possible products than can occur, specifically a racemic mixture of benzoin, racemic mixture of hydrobenzoin, or meso-hydrobenzoin. Therefore, three different tests were conducted in determining the identity of the product: melting point, thin light chromatography, and infrared spectroscopy. (a) Mechanism and reaction equation of benzyl reduction
Stereochemistry plays a vital role in the five possible products of benzil reduction. The five possible products in the reduction of benzil are due to the two carbonyl groups in benzil. If the sodium borohydride reduced only one carbonyl, then the product would be a racemic mixture of benzoin (R,S-). However, if both carbonyl groups are reduced, the possible products will be meso-hydrobenzoin (R,S-) in which the R enantiomers react to create an S chiral center and S enantiomers react to create an R chiral center or the R enantiomers react to create another R chiral center and S enantiomers react to create another S chiral center.
Key experimental details, observations and results Table 1. Amount of Reagent Used | Reagent | | Amount (mL or g) | Benzil | | 1.05g | | Sodium Borohydride | 0.20g | | Ethanol | | 10mL | |
1. Observations: a. When heating mixture of benzil and ethanol, dissolved and became yellow. b. Recrystallization occurred during NaBH4, appeared as small, white foaming bubbles c. Boiled-cloudy yellow color d. Cooling: had a pale yellow clear and white crystals started to appear 2. Description of product: e. Color: white f. Appearance: uniform, shiny, paper-like texture
Results Table 2. Experimental and Literature Melting Points | | | | | Name | | Experimental | | Name | | | Literature | Product | | 132.1 - 134.2°C | | Racemic Benzoin | |