the melting point of the crystal started at 123 degrees and finshed at 130degree
ID: 870440 • Letter: T
Question
the melting point of the crystal started at 123 degrees and finshed at 130degrees celcius. also the product weighed 0.79g.
? Calculate the percent yield and explain your result
? Measure the m.p of the product and compare it to the literature. Explain your result
below is our procedure for the experiment. all the information that was given and we are doing an SN2 reaction creating phenacetin.
Add potassium carbonate (2.0 g, 0.014 mole) and acetaminophenol (103g, 0.0086 mole) to a 50-ml round-bottom flask. Measure iodoethane (1.0 ml, 2 0 g, 0.13 mole) in a 10-ml graduated cylinder and add acetonitrile in portions with shaking to mix up to the 9-ml line of the graduated cylinder. Add the solution to the round-bottom flask and rinse residue in the graduated cylinder into the flask with an additional 7 ml-portion of acetonitrile. Add a couple of boiling chips, attach a reflux condenser, and heat at a slow reflux for one hour. Uneven boiling (bumping) results due to the solid residue in the round-bottom flask not transferring heat evenly. Use a heat setting that just maintains a reflux temperature. Decant the hot solution from the solid residue into a 250-ml beaker labeled with your name and allow sitting in the hood until the next lab period so that the solvent evaporates. Normally solvents are removed by distilling, but in this case as the solvent is removed by heat the formation of the solid product causes uncontrollable splattering. Transfer the solid from the beaker into a 50-ml Erlenmeyer flask, add hot water (20 ml), and heat to nearly boiling. While still heating, add ethyl alcohol in small portions with swirling until the solid dissolves. To remove iodine (from air oxidation of I-) add solid sodium bisulfite to the hot solution in tiny portions with swirling until the addition of additional bisulfite has no effect on the color (which usually goes from pink to a light tan). Allow to cool undisturbed while crystals grow. After crystal growth appears to be complete, cool in an ice bath for a few minutes and then collect the crystals on a Buchner funnel. Wash the product with a small amount of cold water and allow the wet crystals to air dry on a watch glass until the next lab period. Weigh the product and record the yield and place the crystals in a labeled vile to be saved for taking the melting point in Experiment XIII.Explanation / Answer
First we need the molar mass of Phenacetin. According to literature it's 179.22 g/mol. Let's calculate that:
Phenacetin it's CH?CONHC?H?OC?H5 so: (12x10) + (1x13) + (2x16) + 14 = 179 g/mol
Now we have an 1:1 ratio. So:
mass of phenacetin: 179 x 0.0086 = 1.5394 g
%yield = (0.79 / 1.5394) = 51.32 %
According to this, we got only the half of the product. We can assume a few things for this:
- During the first period, it could occur that the solution wasn't heated in the right way, maybe it was heated at medium or high heat. And that affects the reaction and the final yield. It could happen too that the theorical yield, is theorical and we are not taking in consideration the fact of the temperature and pressure system, that's something that always have some kind of effect in the final yield.
- The other thing that could happen (and it's more reasonable) it's the fact that the K2CO3 and the iodoethane were not pure. Maybe they were all impure, and the Purity % of the reactants are something that affects a lot the final yield of the reaction, and also the melting point. So the reactants were not pure and clean, so that affects the final yield of the product.
The m.p. of the literature for phenacetin is 134-137
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