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17 Nov 2019

Draw out the structure of 1,5-pentanediol and n-hexanol, which of these two molecules is more polar than the other? Provide a brief explanation. Which of the above two molecules has a higher Rf value?

A) A student run a TLC on the above two molecules on a TLC plate using a solvent with relatively high polarity. He spotted 1,5-pentanediol towards the left side, and n-hexanol towards the right side of the baseline. Using a ruler to help draw straight lines, draw a hypothesized result of the TLC plate. Determine the Rf values for each molecule.

B)Another student repeated the above experiment, but used a solvent with relatively low polarity. Redraw the hypothesized result of the TLC plate. Determine the Rf values for each molecule.

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Nestor RutherfordLv2

23 Apr 2019

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I have completed this question, but I would like someone to check over my work. I believe I have incorrectly shown some of the intermolecular forces. Below are the directions and my answer. Please check over each part.

Question: The rectangle on the left side is a TLC plate with SiO_2. The eluent used was 5% MeOH in CH₂Cl₂. The molecules spotted on the plate were: 1-cyclohexylethan-1-one, aniline, and (E)-1,2-diphenyethane.

a) draw one (1) molecule of each analyte in the correct relative position on the plate

b) draw two (2) of each solvent molecule type interacting with either the plate or the analytes

c) for all molecules, clearly show the relevant intermolecular forces that explain the TLC results

Answer:

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.

Gather 2 pieces of square filter paper, the scissors, a pencil, and a ruler. DO NOT use a pen

or any form of ink. Create a strip of filter paper that measures 14 cm by 7 cm. See Figure 3.

Use the ruler to measure 14 cm across the edge of the paper. Use the pencil to draw a small

âxâ at 14 cm. On an adjacent edge of the paper, use the ruler to measure 7 cm up the edge

of the paper. Use the pencil to draw a small âxâ at 7 cm. Using the ruler as a straightedge,

lightly trace a rectangle that is approximately 14 cm by 7 cm. Use the scissors to cut out the

rectangle. Create two additional strips of paper.

Note:There should be enough filter paper to create a fourth 14 x 7 cm strip of paper if needed.

2.Gather the 25 mL graduated cylinder, 100 mL beaker, distilled water, and salt. Use the

graduated cylinder to add a total of 50 mL of distilled water to the beaker. Add a pinch of salt

to the beaker. Use the stirring rod to stir the solution until the salt has completely dissolved,

resulting in a salt solution of approximately 0.1% NaCl.

3.Gather 2 sheets of the filter paper â 14 x 7 cm from step 1.

a.Create a base line by drawing a thin horizontal line with a pencil (NOT a pen!)

across the paper, 10 mm (1 cm) from the bottom. The line should barely be visible.

b.With a pencil, draw 9 small cross lines along the horizontal line, 1.5 cm apart,

Experiment

Chromatography of Food Dyes

4.Repeat step 3 for the second piece of filter paper.

5.On Sheet 1, from left to right, use a pencil to lightly label each section between the cross lines

with the abbreviation for the six FD& C food colors from your experiment bag that will be

tested: B1, B2, R3, R40, Y5, and Y6.

6.Also on Sheet 1, after Y6, place the labels KG and KS to represent the Kool-

Grape and Kool-Aid

Â®Strawberry drink mixes to be tested.

7.On Sheet 2 from left to right, use a pencil to lightly label each section between the cross lines

with the abbreviation for the grocery store food coloring that will be tested: SR, SY, SG, and SB.

8.Also on Sheet 2, after SB, place the label âUKâ for unknown and then âMâ plus a letter for the

color of 4 different candies from your bag of M&Ms: such as; M-R (for M&MÂ® red), M-Y, M-B,M-G.

9.Set Sheet 2 aside and perform the following for Sheet 1. After you have completed the

experiment for Sheet 1, repeat for Sheet 2.

10.Put on your safety gloves and goggles.

11.For each dye on the sheet to be tested:

a.Use the scissors to cut open the pipets and place them in the 24-well plate, bulb

side down, using the well plate as a pipet holder.

b.Place a few drops of the dye in a well of the 24-well plate, as shown in Figure 4.

Dye drops and pipets in well

12.Once the paper is spotted with all the dyes, allow the spots to dry for a few minutes.

13.Form the spotted filter paper into a cylinder (colored spots on the inside) with the edges

touching, but NOT overlapped, and staple at the top and bottom as shown in Figure 7. (You

may want to use small pieces of tape on the outside to lightly hold the cylinder together

while you securely staple it. If so, remove the tape after stapling.) Set the cylinder aside for a

moment.

14.The salt water (~0.1% NaCl) you previously prepared will be your eluting solvent and a Petri

dish will be your elution chamber. Pour salt water into the clean and empty Petri dish to a

depth of about 1/4 cm. This is just enough to cover the bottom of the elution chamber.

15.Set your paper cylinder next to (not in) the Petri dish, with the spots at the bottom, and look

to make sure the solvent level is below the base line. If it is not, pour out a little solvent until

it is.The base line (and spots at the bottom of the chamber) must be above the solvent level

for this experiment to work.

16.Carefully place the paper cylinder into the eluting chamber, making sure not to touch the Petri

dish sides. See Figure 8. The solvent-front will travel up the paper rapidly at first and then will

slow down. Let the solvent-front rise, monitoring every few minutes. Immediately remove the

cylinder if any dye or the solvent front moves up higher than 2 cm from the top of the paper.

If all the solvent is soaked up before the front has time to move toward the top of the paper

carefully add a little more solvent to the Petri dish.

17.When the solvent-front has traveled up the filter paper, 2 cm from the top, remove the filter

paper cylinder from the chamber and immediately mark the top the solvent-front, on the dry

part of the paper, with a pencil. See Figure 9.

18.Allow the paper to dry, carefully remove the staples,

and draw an outline around each spot

using a pencil.

19.Take a photograph of your chromatogram after you have circled the spots.

Resize and insert the photograph of your chromatogram in Data Table 1of your

Lab Report Assistant

20.Use the ruler to measure the distance of the solvent front, in millimeters. Use Figure 1 in the

Background section as needed. Record the distance of the solvent front in Data Table 2 of your

Lab Report Assistant

For each of the dye spots on the filter paper chromatogram, measure and record to the

nearest millimeter the distance each of the spots has traveled up the solvent front. Start from

the original horizontal pencil line (base line) and measure to the top center of where the dye

stops in each column on the paper. See Figure 2 in the Background section as needed.

22.Calculate the Rf value for each spot and record in Data Table 2

23.Repeat steps 10 through 22 for the second sheet of filter paper. Record all data for this

chromatogram in Data Table 3 of your Lab Report Assistant

24. Compare the Rf values for the spots of the Kool-Aid Â®, unknown sample, store food colorings,and M&Ms Â®

, to those of the known FD&C food dyes, to determine which FD&C dyes are used in the Kool-AidÂ®, the grocery store food colorings, and in the M&Ms Â®.

25.Record the FD&C dyes present in each of the samples in Data Table 4 of your Lab ReportAssistant

26.Clean up all equipment and return to the lab kit for future use.

27.When you are finished uploading photos and data into your Lab Report Assistant, save your

file correctly and zip the file you can send it to your instructor as a smaller file.

Enter the results from chromatography filter paper Sheet 1 of your experiment in the following tables. If more than one colour is present in a sample, please indicate colour when referring to distance and Rf measurement.

Sheet 1: FD&C Food Colours

Colour	Blue 1	Blue 2	Red 3	Red 40	Yellow 5	Yellow 6	Solvent
Distance (mm)
Rf							--

Sheet 1: Drink Mixes

Substance	Kool-AidÂ® Grape	Kool-AidÂ® Strawberry	Solvent
Distance (mm)
Distance (mm)			--
Rf			--
Rf			--

Enter the results from chromatography filter paper Sheet 2 of your experiment in the following tables. Indicate the colours of M&Ms used in the experiment.

Sheet 2: Store Food Colours

Substance	Store Red	Store Yellow	Store Green	Store Blue	Solvent
Distance (mm)
Distance (mm)					--
Rf					--
Rf					--

Sheet 2: Candy Colours and Unknown

Substance	M&M	M&M	M&M	Unknown	Solvent
	Colour:	Colour:	Colour:
Distance (mm)
Distance (mm)					--
Distance (mm)					--
Rf					--
Rf					--
Rf					--

Answer the following questions based on your experimental results.

Show the calculation for the Rf value for Red40.

What FD&C colour(s) make up the unknown sample?

What FD&C colours make up the food colourings? State the brand used.
What FD&C colours make up the Kool-AidÂ® drinks and M&MsÂ®?

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