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13 Dec 2019

At the start of the reaction in Experiment 8, triethylene glycol is mixed with two other chemicals and heated until it becomes a uniform liquid. What is actually occurring? Choose all of the correct terms from among the following: "melting", "boiling", "dissolving", "emulsifying", "deprotonating", "neutralizing".

1. Place 0.5 g of 1,3-diphenylacetone, 0.5 g of benzil, and 5 mL of triethylene glycol in a 25 mL Erlenmeyer flask.

2. Add a magnetic stir bar and place the flask on a hotplate.

3. Set the temperature control to about “3” and stir the mixture until a homogenous solution is obtained.

**The goal is not to boil here—the boiling point of triethylene glycol is over 280 °C!—nor to accelerate the reaction—the base that causes the reaction to begin is not even present yet. Rather, we just want the starting solid materials completely mixed into a liquid so the reaction can run well once the base solution is added.

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Nelly Stracke
Nelly StrackeLv2
17 Dec 2019

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1. Into a 100 mL round bottom flask place 0.5 g stilbene dibromide, 10 mL ethanol and a stir bar. 2. Add 1.25 equivalents (i.e. 1.25 fold excess) of zinc powder

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This is the description from my organic chemistry lab.

Lab Observations and Data

We obtained 1.17g of cyclohexene oxide (clear liquid) and 3 mL of water into a 50 mL flask with a stir bar. When added a single drop of sulfuric acid, the clear liquid started to change to a very, very light yellow/brownish color. We obtained an ice bath on the side in case our mixture started to boil. After the solution stirred for about 25 minutes, we added sodium hydroxide. We inserted a pH paper and it turned a dark blue, meaning basic. Added another drop of sulfuric acid to make it a little less basic. Added the mixture to a separation funnel, shook it around and ended with separated layers. We separated the layers, thinking the bottom layer was the organic layer, when it was really the aqueous layer. So we ended up mixing the wrong layers back together. After some error, we isolated our new organic layer and added some drying agent. We then put that mixture with the drying agent, NaOH, into the rotovap. Our final product was a white powder and weighed 1.51 grams. We then set up a vacuum filtration while boiling water. We boiled our dried organic layer into the hexane. Added two drops of ethyl acetate to help the boiling process go faster. After vacuum filtering it, it weighed .394 grams. The melting point is 91 to 93 degrees Celsius. Our IR spectra matches the "trans" conformation. So for our TLC plate we observed blue dots to match the trans conformation.

The question is "calculate your percent yield" Which is actual yield/theoretical yield x 100. I just dont understand how I get those numbers.

Here is the lab manual description as well.

Procedure for the Preparation of 1,2-Cyclohexanediol Place a mixture of 1.18 g (0.012 mole) of cyclohexene oxide and 3 mL water into a 50 mL Erlenmeyer flask, equipped with a magnetic stir bar. To this mixture with vigorous stirring add one drop of 6 M sulfuric acid (33% H2SO4) Caution: After a short incubation time, the reaction mixture will become quite warm. This epoxide ring opening reaction is very exothermic. (Why?) If the reaction mixture begins to boil, place the flask in a bath of ice and water. Allow the reaction mixture to stir for the next 15 minutes and let it cool to room temperature. Afterwards, add a small amount of 10% sodium hydroxide drop-wise to neutralize the stirring solution. (No more than 3 or 4 drops of 10% NaOH should be necessary.) Place a drop of the reaction mixture on pH paper to check the pH. Extract the product from the reaction mixture into ethyl acetate or diethyl ether (2 x 15 mL). Dry the combined extracts over sodium sulfate. Decant the solution and remove the solvent to yield the crude product (~1 g). The product can be purified by recrystallization from a small amount (~ 5 mL) of hot toluene or hexanes. Collection of the purified product by suction filtration yields 1,2-cyclohexanediol. The cis isomer has a melting point of 97-101 °C whereas the trans isomer melts at 101-103 °C. Determine the product(s) or products the reaction. Include a percent yield calculation in your report along with the results of your TLC analysis

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