CHEM403 Study Guide - Final Guide: Polyvinyl Alcohol, Silly Putty, Hexamethylenediamine

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orangewolf816

22 Jan 2020

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The production of various polymers and plastic identification using. I. nylon: why are there two distinct layers of liquid when nylon is synthesized?when mixing the adipoyl chloride and hexanediamine results in an organic layer on top of an aqueous layer. The organic layer is more dense while the aqueous layer is more dissolved with the water and is less dense. Slime : summarize the observations you collected when cross-linking pva with borax in. Discuss the effect of successive additions of borax to poly(vinyl alcohol). The cross-linking of pva and borax resulted in a clear substance that seemed to be very sticky and gooey. The substance seemed to have a high viscosity. The more borax that was added, the stickier the substance got: summarize the observations you collected when adding acid (0. 1 m hcl) to the cross-linked pva. Discuss the effect of successive additions of hcl to the slime.

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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 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

Please help me with the following problem. It has many parts to it, but it is one question. Thank you in advance

Synthesis of 1-Bromobutane

Reaction Scheme

NaBr, H2SO4

CH3CH2CH2CH2OH---------------------> CH3CH2CH2CH2Br + NaHSO4 + H2O

H2O

Possible by-products:

1-butene (bp â6.3 ^oC), di-n-butyl ether, C₄H₉OC₄H₉, (bp 141 ^oC)

Properties of reagents and product:

Substance	Mol Wt. (g/mol)	Density (g/ml)	bp, ^oC	Solubility	Hazards
1-butanol	74.12	.81	117-118	Sol water, Miscible alc, ether, and more	Flammable, irritant
H₂SO₄ (con)	98.07	1.84	280	X	corrosive material
sodium bromide	102.89	X	X	X	X
1-bromobutane	137.03	1.27	101.6	Insol in water; sol in alcohol, ether	Flammable, irritant

Quantities used in the reaction and yield data:

Substance	g or mL	Calculated moles	Theoretical Yield moles grams		Actual Yield, grams
1-butanol	mLs		x	x	x
H₂SO₄ (con)	11.5 mL		x	x	x
sodium bromide	13.3 g		x	x	x
Water	15.0 mL	x	x	x	x
1-bromobutane	x	x			Want 7.5 g

A. Assume the above synthesis of 1-bromobutane is known to proceed in 75% yield and you would like to prepare 7.5 g of material. Back calculate how many mLs of 1-butanol you will need for the reaction to synthesize the 7.5 g of product, assuming that the 1-butanol is the limiting reagent. Place this number in the table. Also, calculate all the remaining missing data to fill the table.

Experimental Procedure: The NaBr, 1-butanol, and water are combined in a round-bottomed flask containing a stir bar and cooled to 0 ^oC. Concentrated sulfuric acid is slowly added with stirring. The reaction flask is then prepared for a 50-minute âbriskâ reflux using a heating mantle. After reflux, two layers will be present. The condenser is removed and replaced with a distillation apparatus. Distill the mixture, recording the temperature range, until no more water- insoluble droplets are collected and the temperatures reaches around 115 ^oC. (The boiling point is elevated due to azeotropic distillation of the water with the 1-bromobutane and increasing amounts of sulfuric acid).

B. Propose a way that you could test if the droplets coming over are âwater-insolubleâ.

Be specific with the manipulations, glassware, and what observation you would see.

The collected liquid is transferred to a separatory funnel and 10 mL of water is added. Two layers form, the bottom being the 1-bromobutane layer. The layers are separated, one through the bottom and one through the top, and the separatory funnel is cleaned and dried. The bromobutane layer is returned to the separatory funnel and washed with ice-cold sulfuric acid to remove traces of the starting material, butene and ethereal by-products.

C. Will the top or bottom layer be the bromobutane layer when washing with concentrated sulfuric acid? Why?

The sulfuric acid layer is removed and the 1-bromobutane is washed with 10 mL 3 M NaOH followed by 10 mL aqueous sodium chloride (brine).

D. What is the purpose of each of these washes?

NaOH â

Brine -

Care should be taken to save the correct layer. The 1-bromobutane is then dried over anhydrous CaCl₂.

E. How will you decide how much drying agent to use? How will you know that the 1-bromobutane is dry.

The product is distilled to obtain a clear, colorless liquid.

F. TLC â Suppose you wanted to follow the above reaction by TLC.

a. Describe how you would go about finding a good solvent or solvent pair to use.

b. Suggest a specific solvent system you would try.

c. Draw below what you would want the TLC plate to look like and show the expected relative R_f values for the 1-butanol and 1-bromobutane. Label the spots, baseline, and solvent front.

For the lab below, what is the separation scheme?

Elimination of 1-octanol.

Apparatus Assembly:

Set up a distillation apparatus.

Using a preweighed 50-mL round-bottom flask as the distilling flask, add 7.5 mL of 1-octanol and weigh it again to determine the exact amount added. Add 2.0 mL of 85% phosphoric acid and 30 drops of concentrated sulfuric acid. Add a magnetic stir bar.

Use a 25 mL round-bottom flask as the receiving flask. Be prepared to immerse it into an ice bath to ensure that no octene vapors will escape into the lab; however, do not add the ice until after the distillation is underway or you will have extra water in your product (from condensation). Even more effectively, you can ice your condenser circulator, but don't do that until after distillation commences either.

Dehydration:

Ensure that the water is flowing in your condenser and begin to heat the distilling flask on the appropriate insert of your heater/stirrer.

The heating should be regulated because ideal time of the distillation should be 30 minutes. Too fast of a distillation will cause an incomplete reaction and isolation of the starting material. The temperature registered by your thermometer will rise very slowly at first, but when the refluxing (soon to be distilling) vapors hit the thermometer, the temperature will rise quickly. It should stabilize as the first condensate begins to form in the distillation condenser; from that point to the end of the distillation, record the range of temperatures: this is your boiling-point range (although in this experiment, the broad distribution of products may cause a broad range of temperatures).

Ideally, you do not want to collect distillate until the temperature is at least 110Â°C (as the distillate, below this temperature, is mostly water); however, since you will have to remove water anyway, this is not critical. However, you don't want to collect product at temperatures much above the boiling point of the octenes since that will increase contamination of your product with unreacted 1-octanol and S_N1 ether byproduct.

Continue the distillation until no more liquid is collected or until tar begins to form; if tar begins to form, stop the distillation. Be sure to not distill the reactants completely, as you will be left with a thick residual tar that will be nearly impossible to remove from the flask.

Isolation and Drying of the Product:

Transfer the distillate to a separate container (flask or separatory funnel) with the aid of an approx. equal quantity of saturated sodium chloride solution (brine). Allow the layers to separate; remove the bottom aqueous layer (using a Pasteur pipet if you chose a flask) and discard it.

Transfer the organic layer (using a dry Pasteur pipet if you chose a flask) in the container to a small round-bottom flask and add a small amount of anhydrous sodium sulfate. Stopper the flask and allow it to sit for 10-15 minutes.

When the product is dry, transfer it to a pre-weighed screw-cap vial (preferably with a Teflon liner) and obtain its mass. Then filter a solution of dichloromethane and product into a GC vial, properly label it, and submit it to the GC vial collection box. The proper ratio of product in dichloromethane is 1 drop in 1-1.2 mL DCM: one drop in a full syringe of DCM.

For this experiment, you will also be required to set up the GC-MS to run your sample by adding your run to the instrument sequence. Follow the instructor's instructions with regard to this task.

CHEM403 Study Guide - Final Guide: Polyvinyl Alcohol, Silly Putty, Hexamethylenediamine

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