CHE 211 Study Guide - Midterm Guide: Separatory Funnel, Benzyl Alcohol, Diethyl Ether

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Experiment Notes (Midterm)

Reduction of Monosaccharides (Carbonyl Reduction)

 The starting reagents are benzaldehyde + the reaction solvent (ethanol); regent NaBH4 is also added

 A TLC sample is ran before the reaction begins; this can be seen on the left; every time a TLC sample is ran, the

clock moves forward by 5 minutes

 Each TLC sample takes 5 minutes to run and then the reaction is forwarded 1 minute before the next one can be

run

 Reaction starts at 7:02pm; the reaction completed at 7:51pm; which makes it roughly 50 minutes to complete

 The final products are ethyl alcohol and benzyl alcohol; the products are transferred into a separatory funnel

where NaOH is added (0.1M)

 Then 2 layers are formed: Aqueous and Organic; the aqueous layer is at the bottom that only contains water;

the organic layer (lower density) is at the top containing benzyl alcohol and diethyl ether

 Benzyl Alcohol is our final product

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Esterification of Fatty Acids (Esterification Reaction)

฀ The starting materials are acetic acid, ethanol and the solvent (diethyl ether); reagent sulfuric acid (H2SO4) is

also added to the reaction flask

฀ The start time is 11:20pm; after the first 10 minutes, ethyl acetate is formed; after 110 minutes, all the starting

material is gone; the only thing left is ethyl acetate, sulfuric acid and diethyl ether

฀ The reaction mixture is extracted with NaOH (0.1 M)

฀ 2 layers are formed; the organic layer is at the top containing diethyl ether; and the bottom aqueous layer

contains ethyl acetate and water

฀ Distilling apparatus is set up to separate ethyl acetate and water; N2 gas is added the apparatus so that the

reaction apparatus DOES NOT explode

฀ The starting temperature of the distilling apparatus is 25.00 C;

฀ +1 minute = 34.50 C

฀ +1 minute = 45.8 C

฀ +1 minute = 56.20 C

฀ +1 minute = 71.80 C

฀ +1 minute = 77 C (this is the boiling temperature of ethyl acetate)

฀ After 5 minutes, it is the first sign of ethyl acetate distillate; after about 33-34 minutes, all of the ethyl acetate

has been distilled and it is collected in the collection flask; in the reaction flask, only water remained

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Document Summary

The starting reagents are benzaldehyde + the reaction solvent (ethanol); regent nabh4 is also added. A tlc sample is ran before the reaction begins; this can be seen on the left; every time a tlc sample is ran, the clock moves forward by 5 minutes. Each tlc sample takes 5 minutes to run and then the reaction is forwarded 1 minute before the next one can be run. Reaction starts at 7:02pm; the reaction completed at 7:51pm; which makes it roughly 50 minutes to complete. The final products are ethyl alcohol and benzyl alcohol; the products are transferred into a separatory funnel where naoh is added (0. 1m) Then 2 layers are formed: aqueous and organic; the aqueous layer is at the bottom that only contains water; the organic layer (lower density) is at the top containing benzyl alcohol and diethyl ether.

Related Questions

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.

I'm currently taking ochem part 2. I need to perform an acid-base extraction to separate out a mixture of solid organic compounds consisting of 50% 2-chlorobenzoic acid; 40% methyl 4-aminobenzoate; 10% 1,4-dibromobenzene. I need to create a procedure to first separate the compounds. I also need to recrystallize each compound after separating the compounds; therefore, I need to know which solvent to use for each compound. I also need to prove that I separated my compounds successfully using TLC (therefore I need to know which solvent to use for TLC). I need to do this as a micro-scale procedure (therefore, I will not be given large quantities of reagants). I'm given the reagants methanol, ethanol, methylene chloride, hexane, 1M NaOH, 6M NaOH, 1M HCl, 6M HCl, Anhydrous sodium sulfate, saturated sodium chloride, acetone, sodium bicarbonate, diethyl ether. I believe we will be given about 2 grams of the solid organic compound mixture.

Note: I want to run this acid-based extraction without using the separation funnel. Can I use a centrifuge tube instead?

I have a rough procedure of how to carry out the acid-base extraction that I've posted below, please look over my rough procedure of the acid-based extraction portion and tell me if the amounts of reagants look okay and if the process is okay. I also have accompanied this with a couple of follow up questions in regards to the acid-based extraction, recrystallization, and running the TLC all accompanied with subheadings.

OFFICIAL PROCEDURE:

Put 0.090g of solid organic mixture into a large test tube. Add 0.5 mL of diethyl ether at a time and stir until all dissolves. If needed, slowly add more diethyl ether solvent. Use minimal solvent.

Extracting methyl 4-aminobenzoate

1. Add this mixture in large test tube into a glass centrifuge tube (labeled âworking reactionâ).

2. Add 1mL 1.0 M HCl to the centrifuge tube. Shake gently and vent. Do this until layers separate. If needed, centrifuge.

Diethyl ether density: 0.713 g/cm3

Waterâs density: 1.00g/cm3 (aqueous layer)

Because diethyl ether has a lower density, it will be on the top layer and consist of the 1,4-dibromobenzene and the 2-chlorobenzoic acid. The bottom aqueous layer will consist of the conjugate acid of the organic base, methyl 4-aminobenzoate because H3O+ protonates the amine of the base to produce an ammonium salt, which is ionic and therefore aqueous in solution. (DRAW THIS OUT)

3. Extract out lower aqueous layer (consisting of the conjugate acid i.e. the ammonium salt, of methyl 4-aminobenzoate) into labeled test tube (ammonium salt).

Note: It is okay to extract a little more out from the bottom bleeding into the organic layer; throw that into the waste to ensure that all that is left are the other 2 organic compounds in diethyl ether. Parafilm.

4. Into the test tube with the ammonium salt, add 6.0 M NaOH DROP BY DROP until the solution returns to become BASIC, this has reproduced the organic base, methyl 4-aminobenzoate. Check with pH paper.

5. Collect the crude methyl 4-aminobenzoate precipitate by filtration using Buchner funnel.

6. Recrystallize from HOT WATER.

6. Filter the pure methyl 4-aminobenzoate precipitate by filtration using Buchner funnel.

Extracting 2-chlorobenzoic acid

1. The âworking reactionâ centrifuge tube now consists of the solvent (diethyl ether), 1,4-dibromobenzene, and 2-chlorobenzoic acid. Add 1 mL of 1.0 M NaOH. Shake and vent. Centrifuge if necessary. Again, as before, the lower layer is aqueous and the top layer is the organic layer (diethyl ether + 1,4-dibromobenzene)

NOTE: B/c NaOH was added, the 2-chlorobenzoic acid was deprotonated to yield a sodium salt, which produced its conjugate base. The salt is ionic and therefore soluble in water.

2. Extract out the bottom layer with Pasteur pipette (contains conjugate base of 2-chlorobenzoic acid) into test tube labeled sodium salt.

Note: It is okay to extract a little more out from the bottom bleeding into organic layer; throw that out into the waste to ensure that all that is left is 1,4-dibromobenzene in diethyl ether. Parafilm.

3. Into the test tube with the sodium salt, add 6.0 M HCl DROP BY DROP until the solution returns to become ACIDIC. This has now reproduced the organic acid, 2-chlorobenzoic acid.

4. Recrystallize with what solvent?

Extracting 1,4-dibromobenzene

1. The âworking reactionâ centrifuge tube should now only contain diethyl ether, 1,4-dibromobenzene with some potential water. Add sodium sulfate to dry out the remaining water. Extract the solution (leaving behind the sodium sulfate ppt) into a test tube labeled 1,4-dibromobenzene.

2. Place the test tube labeled â1,4-dibromobenzeneâ in a hot water bath and boil to that of the solvent (diethyl ether) at 40C.

3. Diethyl ether has a low boiling point of 34.6 C whereas 1,4-dibromobenzene has a high boiling point of 220.4C.

4. Therefore, the remaining organic layer in the âworking reactionâ centrifuge tube now only containing 1,4-dibromobenzene and diethyl ether can be separated by evaporating diethyl ether.

5. Recrystalize with what solvent?

Acid-Based Extraction Questions:

Q1: Is diethyl ether a good solvent for initially dissolving all three solvents for the acid-base extraction? And if so, how much solvent do I need to add? I thought minimal enough to dissolve the organic comopunds?

Q2: Are my rough amounts of reagants used correctly for the acid-base extraction?

Q3: Should I add anhydrous sodium sulfate to my last step of acid-base extraction which consists of the diethyl ether and 1,40-dibromobenzene because there might be some aqueous layer left?

Q4: Can I perform my acid-base extractions with a centrifuge tube instead of a separation funnel?

Q5: Should I start off with more grams of my organic mixture when I begin? Is 0.090 grams too small?

Recrystallization Question

Q6: Which solvents for each isolated crude compound should I use for recrystallization? Do I need to run a test for a suitable solvent? If so, which solvents are good to start with. I was thinking water and methanol.

a) I was thinking of using hot water as the hot solvent for methyl 4-aminobenzoate and for 2-chlorobenzoic acid. Is this correct to do so?

b) Which solvent should I also use to recrystallize 1,4-dibromobenzene?

TLC Question

Q7: Which solvent should I use to run the TLC for my organic compounds. After I know which solvent I will be using, where should I expect each compound to travel relative to the other organic compounds? (i.e. closest to the solvent line, middle of the solvent line, furthest from solvent line).

Miscellaneous Question

Q8: What's the point of telling me the percentages of the compounds in the mixture? Does that affect how much reagant I should be using during the acid-based extraction?

CHE 211 Study Guide - Midterm Guide: Separatory Funnel, Benzyl Alcohol, Diethyl Ether

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