Lab+Report+For+Baker+Yeast+TL

Thomas Lewis Lab 243 4/24/11 Enzymatic Reactions: A Chiral Alcohol from a Ketone And Enzymatic Resolution of DL-Alanine __Introduction__ Many different enzymes are present in the form of yeast, in this lab experiment this fermentation of yeast allows for certain ketones within the yeast molecules to be reduced into chiral alcohols. Misunderstanding here: the ketone we are reducing is ethyl acetoacetate, which we are adding into the solution containing the yeast. So the yeast is reducing something very specific. Whenever a chiral product is produced from an achiral starting material the chemical and optical yield are very important, the steroselctivity of this reaction is critical. The methods for calculating the end results are looking at the enantiomeric excess that is produced. A sodium borohydride reduction will produce 50% R and 50% S alcohol with no enantiomer in excess. If 93% S-(+) and 7% R-(-) isomer are produced, then the enantiomeric excess is 86%. In the yeast reduction of ethyl acetoacetate it has been tested and reported to have around enantiomeric excesses ranging from 70% to 97%. This optical yield is very distinct from the chemical yield, which depends on how much material is isolated from the reaction mixture. The use of enzymes to carry out stereospecific chemical reactions is new, but it is not always possible to predict if an enzymatic reaction ( unlike a purely chemical reaction) will occur or how stereo specific it will be if it does take place. Because the yeast reduction of ethyl aceoacetate is easily carried out, it might be an interesting research project to explore the range of possible ketones that yeast will reduce to chiral alcohols. __Procedure__ 1.) In a 25 ml flask dissolve 2.3 g of sucrose and 15 mg of disodium hydrogen phosphate in 8.5 ml of warm (35 degree Celsius) tap water. Add 0.5 g of dry yeast and swirl flask until yeast is suspended into the entire solution. Repeat this step for four separate flasks to construct multiple attempts for recording data. After 15 minutes of wait time and after the yeast has visibly started fermenting add 150 mg (1.5g) of ethyl acetoacetate. Add to each flask and store flasks in a warm place ideally 30-35 degrees Celsius for 48 hours or more to allow all the yeast to ferment properly. 2.) After the fermentation process add 0.5 g of Celite filtration aid and remove the yeast cells by filtration on a Hirsch Funnel. Wash the cells with 1.5 ml of water, and then saturate the filtrate with sodium chloride to decrease the solubility of the product. Refer to the handbook to find the solubility of sodium chloride in water to determine exactly how much to use. In each flask extract the resulting solution five times with 1.5 ml portions of ether in each test tube, taking special care not to shake up the tube and mix the layers of the solution. Add small amounts of methanol to help break up emulsions. Dry the ether layer by adding anhydrous sodium sulfate or calcium chloride pellets until drying agents no longer clump together. After a 15 minute wait period filter the ether solution into a tarred flask and evaporate the filtrate, keeping in mind that the remaining residue should weight around 100 mg (1 g). It should unlike the starting material have a negative ion chloride test. It is then ready to be sampled and tested for the data to be complied for the IR spectormotior which should show the hydroxyl group and may show the unreduced methyl ketone. The NMR spectrum of the product is easily distinguished from that of the starting material. __Data__

__Analysis__

__Conclusion__

What happened here? This report is seriously incomplete.