Supplementary Information s5

Supplementary Information

List of chemicals and CAS numbers S1

Pre-lab questions S2

Experimental Procedure S4

List of Mixtures S8

Assessment Rubric S13

List of chemicals and CAS numbers

Chemical / CAS number
Diethyl ether / 60-29-7
Dichloromethane / 75-09-2
Sodium hydroxide / 1310-73-2
Hydrochloric acid / 7647-01-2
Sodium hydrogen carbonate / 144-55-8
Sodium chloride / 7647-14-5
p-nitrobenzoic acid / 62-23-7
ethyl 4-nitrobenzoate / 610-34-4
D,L-phenylalanine / 150-30-1
N-Acetyl-D,L-phenylalanine / 2901-75-9
N-Acetyl-D,L-phenylalanine methyl ester / 62436-70-8
2,6-dimethylaniline / 87-62-7
α-Chloro-2,6-dimethylacetanilide / 1131-01-7
Paracetamol / 103-90-2
Ethyl benzoate / 93-89-0
4-aminophenol / 123-30-8
Salicylic acid / 69-72-7
4-methoxyacetanilide / 51-66-1
Sesamol / 533-31-3
Sesamol allyl ether / 19202-22-3
p-Anisidine / 104-94-9
Benzoic Acid / 65-85-0
Magnesium sulfate / 7487-88-9

Pre-Lab questions and results

The pre-lab questions were delivered and graded as a multiple choice quiz using Blackboard. The quiz was available to the students from one week before the students were scheduled to start this experiment until 12.00 am of the day of the experiment. Grades were converted into a mark out of 10 and added to the assessment rubric. Answer’s to each question is given in brackets after the answer.

Pre-lab quiz

Read through your script and watch the videos located in the experiment O6 folder. If you haven’t done so already, look through the information about how to write your laboratory report including the parts to complete before starting your experiment. Also read your CHEM1000 notes by Professor Nelson about pKa and how solvent extractions work. When you have done this answer the questions.

Check box to confirm you have understood the instructions

The following questions will help you with part 1 of the experiment – designing a purification of a mixture.

1. What does the pKa value of a given compound represent?

a) The pH at which a molecule is fully dissociated

b) The pH at which a molecule is half dissociated (Answer)

c) The pH at which a molecule is not dissociated

2. What is the typical pKa value of a carboxylic acid?

a) 0

b) 5 (Answer)

c) 10

d) 15

3. What proportion of acetic acid and acetate would there be in a solution at pH 10?

a) all acetic acid

b) some acetate but mainly acetic acid

c) equal amounts of acetic acid and acetate

d) mostly acetate but some acetic acid

e) all acetate (Answer)

Feedback: Because a solution of pH 10 is several orders of magnitude higher than the pKa value of acetic acid (4.7), it is fully dissociated.

4. A mixture of aspirin, aniline, paracetamol, and calcium chloride is partitioned between diethyl ether and water. Which of these compounds will dissolve in the aqueous layer? Click all that apply.

a) aspirin (answer)

b) aniline

c) paracetamol

d) calcium chloride (answer)

5. A mixture of aspirin, aniline, paracetamol, and calcium chloride is partitioned between diethyl ether and 2M sodium hydroxide solution. Which of these compounds will dissolve in the aqueous layer? Click all that apply.

a) aspirin (answer)

b) aniline

c) paracetamol (answer)

d) calcium chloride (answer)

Feedback: CaCl2 is a salt so will dissociate in both water and 2M sodium hydroxide. The carboxylic acid of aspirin has a pKa of 5, the phenol of paracetamol has a pKa of 10, and the amine of aniline has a pKa of 35. Water has a pKa of 7 so aspirin partially deprotonate and dissolve in the aqueous layer, whilst paracetamol and aniline will remain protonated and soluble in the organic layer. Sodium hydroxide has a pKa value of 15 so it will fully deprotonate both aspirin and paracetamol but not aniline.

6. Design a work-up flow chart and write this in your experimental write-up. This will be checked by a demonstrator before you can start.

Check box to confirm you have understood the instructions

Experimental Procedure

Reaction Overview

Design work-up procedure for a given reaction mixture

Previous Key Skills/Techniques required: solvent extraction, drying with MgSO4, using a rotary evaporator, infra-red spectroscopy

New Key Skills/Techniques required: Experimental design, problem-solving.

As you have experienced, mixing together reagents is not the only important part of an experiment. After this, products are separated from their impurities by a work up procedure (often a solvent extraction) and sometimes further purification is also required, but how do chemists design this part of the experiment?

To design a successful work-up procedure, the chemist must draw upon their knowledge of the physical and chemical properties of molecules to manipulate the solubility of a chemical in organic and aqueous solutions.

You will need to use your notes on purification and pKa in CHEM1000 ‘Modern Chemistry’ and Chapter 8 of ‘Organic Chemistry’ by Clayden, Greeves and Warren to help you through this experiment.

Objectives and planning your work

· You will purify a mixture of compounds by a liquid-liquid separation technique.

· Each group will be given a different reaction mixture to design a work-up for. This can be found in the O6 folder of the VLE.

· In this experiment we are judging you on the purity of each compound, the yield is not as important.

Pre-lab exercises

Your pre-lab exercises for this experiment are:

· Complete the pre-lab exercises to help you become familiar with how to design a work-up.

· A work-up procedure you will design and use in this reaction. This must be completed by the time you start your reaction.

Designing your work-up

You will be given a mixture containing two or more organic compounds. You will use a standard organic-aqueous work-up using a separating funnel [as you did in experiment O1] to cleanly isolate the certain compounds in the mixture.

Which compounds will be in my mixture?

The mixture that you will be purifying is dependent on the week you are performing the experiment. The list is available in the O6 folder of the VLE. Make sure you have chosen the correct mixture of compounds to purify.

By using your knowledge of solubility and acidity, you should be able to manipulate which components go into the aqueous or organic phase. We strongly recommend you answer the questions 1-5 of the pre-lab quiz before designing your work-up.

You will have the following organic and inorganic solvents available to use:

Organic Solvents

Diethyl ether (Et2O)

Dichloromethane (DCM)

Aqueous Solutions

Water

2M NaOH (aq)

2M HCl (aq)

Saturated NaHCO3 (aq)

Brine (saturated NaCl) (aq)

COSHH Assessment

Personnel Involved: Undergraduates, laboratory demonstrators, laboratory staff

Chemical / Hazard / Precautions
Diethyl ether
/ Extremely flammable liquid and vapour.
Harmful if swallowed.
May cause drowsiness or dizziness. / Wear gloves
Keep away from flames/sparks/
hot surfaces
Dichloromethane
/ Possible carcinogen
Vapours may cause drowsiness
Irritant / Wear gloves
Avoid breathing vapours
2M Sodium Hydroxide (aq)
/ Causes severe burns and eye damage / Wear gloves
2M Hydrochloric acid (aq)
/ Corrosive
Harmful by inhalation / Wear gloves
Avoid breathing vapours
Sodium hydrogen carbonate / No associated hazards
Sodium chloride / No associated hazards
Magnesium sulfate / No associated hazards

Procedure

Your laboratory write-up will be slightly different to experiments O4 and O5. See the O6 folder in the VLE for further advice. Design your work up by constructing a flow chart in your laboratory notebook.

You must have your work-up flow chart designed and signed by a demonstrator before starting. Failure to do so will mean you cannot start your experiment.

To any organic solution containing one of the compounds you are trying to isolate, dry with MgSO4, then remove the MgSO4 by filtration. Remove your solvent on a rotary evaporator.

Record a yield of your product.

Product ______g; ______%

Record an IR spectrum of your product [watch the video if you are unsure what to do] and attach the spectrum to your laboratory notebook. Assign the peaks of the spectrum to your product in the results section.

Transfer into a sample tubes (available in a drawer in your bay) and label the tube as shown:

Make sure you have isolated all the compounds you are required to and have an IR spectra of each one.

Complete your laboratory report continuing from the pre-lab section.

Part 1 should include:

· Your work-up flow chart

· Your work-up written as an experimental procedure

· A discussion of your purification procedure

· Attached IR spectra and interpretation

CHECKLIST – make sure you have obtained all these before having your experiment marked

§ Samples of all your products in labelled vials

§ Infra-red spectra of your products

§ Completed laboratory write up.

List of mixtures

Make sure you are purifying the correct mixture based upon your start date of experiment O6. Isolate the compounds that are boxed.

Week / Mixture
14 /
15 /
16 /
17 /
18 /
19 /
20 /
21 /
22 /

Week 14 Mixture

COSHH Assessment

Section: Priestley Laboratory Experiment: O6 – Experimental design