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26 Nov 2019

I Need Help With These Couple Of Problems On My Worksheet

1. The amount of heat absorbed by a melting solid is related to theamount of heat lost by a solidifying liquid how?

2. How much heat does it take to make 70g of water boil at 100C?

3.When 15g of diethyl ether (C4H10O) is converted to vapor at itsboiling point about how much heat is absorbed if Delta Hvaporization is 15.7 kj/mol and the boiling point is 34.6 C?

4. If you have 75g of ice and you want to vaporize it how much heatwould be needed? The specific heat of water is 4.18j/g C?

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Jarrod RobelLv2

3 May 2019

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Organic chemistry

Part1

Question1:

Page 1 of 3 In this session you will carry out two experiments to demonstrate chemistry of the carbonyl group. The two step synthesis of an amide from a ketone in Part 1 involves a nucleophilic addition reaction. In Part 2 you will convert an unknown amine to an amide using Part 1 Two Step Synthesis of an Amide from a Ketone This laboratory activity involves the synthesis of an amide from a ketone in two steps. In the first step, benzophenone is converted to diphenylmethanone oxime (Scheme. This reaction is a straightforward nucleophilic addition of an amine to a carbonyl that occurs with elimination of a water molecule. In the presence of phosphorus pentachloride, the oxime e (Scheme 2). The mechanism for the second step is less straightforward and your demonstrator will discuss it with you during the laboratory class. The intermediate oxime and the amide final product have the same molar mass and molecular formula, you will see how they may be differentiated using spectral data. 0 N-OH 1. HONH2H, NaOH + H20 Scheme 1 Scheme 2 Conversion of the ketone to an oxime (nucleophilic addition) Place the following in a 50 mL round bottom flask: Benzophenone (2.5 g), hydroxylamine hydrochloride (1.5 g), ethanol (5 mL) and water (1 mL). Add sodium hydroxide pellets (2.8 g) in portions with swirling and if vigorous reaction occurs, cool the flask under running tap water, When all the sodium hydroxide has been added, attach a reflux condenser and boil the mixture for 5 minutes. Allow the mixture to cool while you prepare an acidic solution by adding concentrated hydrochloric acid (7.5 mL) to water (50 mL) in a 100 mL beaker. Pour the cooled reaction mixture into the acidic solution and isolate the precipitate using vacuum filtration. Wash the solid with cold water and dry in an oven at 40Â°C or in a vacuum desiccator. Record the melting point and the yield of the oxime. Using the balance in the fume hood, rapidly weigh out phosphorus pentachloride (2.5 g) into a plastic vial. In a 100 mL conical flask dissolve the oxime prepared earlier (2.0 g) in dry diethyl ether (30 mL). Cool the flask in an ice bath and add about half of the phosphorus pentachloride. When the heat generated in the reaction subsides, add another small portion of phosphorus pentachloride and continue this process until all the material has

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 Â°C whereas the trans isomer melts at 101-103 Â°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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