I would like to get help to make short discussion report of experiment: Elimination Reactions and Gas Chromatography. This is my question: Do the GC results match with the expected product distributio

1 Experiment 2 : Elimination Reactions and Gas Chromatography Elimination Reactions : One method of preparing alkenes is to do an elimination reaction on alkyl halides. See your textbook to review the theory on this. In this experiment, you will be conduct ing one of four different reactions in an attempt to produce alkenes. Reacting either 2 -bromopentane or 1 -bromopentane with either sodium ethoxide or potassium tert -butoxide results in a total of four different reactions: 1) 2) 3) 4) From your background on substitution and elimination reactions, you should be able to predict the approximate relative amounts of any expected products. From the standard chromatogram of the mixture of 1-pentene, cis -2-pentene and trans -2-pentene that is given in the lab, you will be able to check your prediction as it pertains to these compounds. Each student will be assigned only one of these reactions to conduct and analyze and then all results will be tabulated so that students can check their predictions from the other reactions as well. 2 Experimental : Read the sections on reflux and dry reflux, drying agents, as well as extraction and washing (macroscale and microscale) of Zubrick. Week 1: You w ill be assigned a brominated alkane and a base for your particular elimination reaction. Note: the sodium ethoxide and potassium tert -butoxide salts will decompose on prolonged exposure to moisture in the air and so should be kept closed to the atmosphere as much as possible. In a 25 mL RB flask set up for reflux with a drying tube, 1.0 mL of the 1.5 M sodium ethoxide or potassium tert - butoxide salt 1 is stirred with 8 drops of the brominated alkane (approximately 7 x 10 -4 moles) at 80 - 90 0C in a water bat h for one hour. After the solution is cooled to ro om temperature, 10 mL of t -butyl methyl ether is added and then washed with saturated aqueous ammonium chloride (2 x 10 mL) and water ( 2 x 10 mL). - That is: add 10 mL of ether and transfer to the 35 mL test tube. Then add 10 mL of saturated aqueous ammonium chloride and mix the two solutions. Separate the two layers. Take the layer you believe to be the organic layer (diethyl ether) and add the second 10 mL of saturated aqueous ammonium chloride [if y our original choice was, indeed, the organic layer, the two solutions will once again be immiscible - if your original choice was, instead, the aqueous layer, the two layers will be miscible and no separation will result]. Once again, separate the organic and aqueous layers. Then add 10 mL of water to the organic layer, mix and separate the two layers. {The end result here is that the organic product was dissolved in an organic solvent washed with two 10 mL portions of a saturated aqueous ammonium chlorid e solution and then once with 10 mL of water.} The organic layer is transferred to a dry test tube and dried with anhydrous magnesium sulfate until GC analysis is performed. Wrap the test tube and cork with parafilm to ensure a good seal. 1These salts have been prepared for you by reacting 0.15 moles of solid sodium or potassium with 110 mL of ethanol or tert -butyl alcohol, respectively, and stirring at room temperature under a drying tube in the fume hood until dissolution of the metals is complete, and then immediately transferring the solutions to sealed containers until use. For week 2, read the chapters on Chroma tography and Gas Chromatography in Zubrick. In the Gas Chromatography chapter, you need not read the ‘electronic interlude’ section. Note (1): In the sample preparation section, Zubrick writes that “for any single experiment t ha t uses GC...the temperature ...will be fixed. ” This is not always the case, and indeed, in this experiment we will be using a temperature program, such that the temperature in the column changes as the run progresses, in order to obtain good separation of compounds as quickly as possible. We keep the temperature relatively low so that all of the different alkenes that might be produced are on the column long enough to be separated and then raise the temperature later in the analysis s o that all of the solv ent and other organics are expelled quick ly before the next run begins. The separation of compounds in GC is based on flow rate of carrier gas, temperature and type of column - experimenters normally 3 have to determine the optimal set of parameters for the particular analysis they are working on, while here the parameters have already been determined for you. Note (2): We will not be using the air peak to signal the start of the chromatogram, but, instead, pressing start on the GC and the chart recorder/inte grator immediately after injecting the sample.] At the beginning of week 2 , you will be introduced to the gas chromatography instrument . Just prior to analysis, filter approximately 1 mL of sample off of drying agent through a filter -tip pipet and dispen se into a GC sample vial. See your instructor for GC instructions. Pre -lab Questions : 1. Draw and name all of the expected products from the reactions 1) to 4) used in this experiment. Comment on the relative amounts of each expected. 2. Explain wh at is meant by ‘retention time ’ in GC and compare this with ‘retention factor (or R f)’ in TLC.