BTEC Appl Science Unit 14

Hi All,

After a little bit of input/ideas. For this unit, and assignment D - the students have 3 preparations to do: non-carbonyl, carbonyl and an aromatic. I am ok with the first 2 - but the 3rd - the prep notes given to me have suggested preparing 4-nitrophenol - does any one have notes/links I can read up on this, just cant find a lot just at the moment?

Thanks in advance

Al
 

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If they have to synthesize an aromatic compound surely the easiest one to do is making aspirin from Oil of wintergreen. It's PAG 6.1 for OCR A-Level Chemistry A.
My Y13 students are currently in the process of carrying out this practical.
 

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I did find the following on a little research - it seems quite complex for School/College Students (and requires a lot of phenol!!!!!)

upload_2018-3-22_10-42-56.png

Surely there are many better methods for synthesizing an aromatic compound : Aspirin, benzoic acid, methyl 3-nitro benzoate just to name a few, which should be less problematic than the process outlined above. Also I would be surprised of the exam board running this BTEC don't accept any of these three mentioned as the practical procedures are still high level and will serve the students well for studying Chemistry at University.
 
I also found the nitration of phenol from the RSC, and got it to work with a little alteration. I did read up and it does seem to specify the addition onto an aromatic ring :S, and not the a subsitution/addition to a side chain/group - so aspirin and esters are out. The 2 practical does call for preparation of an organic with a carbonyl group so esters will work for that part fine :)
 
I did find the following on a little research - it seems quite complex for School/College Students (and requires a lot of phenol!!!!!)

View attachment 1258

Surely there are many better methods for synthesizing an aromatic compound : Aspirin, benzoic acid, methyl 3-nitro benzoate just to name a few, which should be less problematic than the process outlined above. Also I would be surprised of the exam board running this BTEC don't accept any of these three mentioned as the practical procedures are still high level and will serve the students well for studying Chemistry at University.
There are phenol substitutes available such as Hydroxybenzoate. David The RSC resource mentioned - Paracetamol- A Curriculum Resource is excellent but can I refer you to a typographical error in the section British Pharmacopeia Method for quantifying Paracetamol using Ammonium Cerium (IV) Sulphate. The oxidation of 4-Aminophenol by Ammonium Cerium (IV) Sulphate should result in Iminoquinone and Ce3+ not Ce4+. Also the colour change is from red to Sky Blue but tha actual end point is the first appearance of the Sky Blue.:);)
 
Hi everyone, doing the PAG 6.1 at moment. However when the students add the glacial acetic acid in part 2 & filter, the filter paper dissolves. Any help/advise appreciated
 

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Hi everyone, doing the PAG 6.1 at moment. However when the students add the glacial acetic acid in part 2 & filter, the filter paper dissolves. Any help/advise appreciated
Hi Toni.

My chemists followed the porcedure below and the filter paper didn't dissolve, the key is to use COLD glacial, so I put the bottle in an ice water bath.

upload_2018-6-14_13-25-47.png
 
Hi 007, thanks. I did follow the given recipe (as above) & placed the glacial acetic in the fridge . However for every one that filters ok, 3 don't. I you place the filter paper in a beaker with ethanoic anhydride & glacial acetic, the paper stays ok. However, if you place it in ethanoic anhydride & some water, the paper looses its integrity. So we're wondering if the problem is with wetting the paper first. Going to try wetting with Glacial instead of water
 
Hi 007, thanks. I did follow the given recipe (as above) & placed the glacial acetic in the fridge . However for every one that filters ok, 3 don't. I you place the filter paper in a beaker with ethanoic anhydride & glacial acetic, the paper stays ok. However, if you place it in ethanoic anhydride & some water, the paper looses its integrity. So we're wondering if the problem is with wetting the paper first. Going to try wetting with Glacial instead of water
Hi Toni. I'd probably not put the Glacial Acid in a Fridge unless you have a Spark-Proof Fridge. Otherwise you may end up with the Fridge door in your face. I'd put it in an external "Ice Box".:);)
 
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Other thoughts Toni. Before carrying out this practical I bought brand new ethanoic anhydride, which compared to previous years made the practical more successful. Over time the anhydride once opened absorbs water and becomes ethanoic acid again, this could have affected your results. Also I chose slow rate filter paper as the filtration under pressure method allows better crystal formation, which in turn allows you to collect a good sample to test its MP.
 
When I do it, we use number 42 filter paper, but looking at your method, it is a little different.

This one was modified to take into account our particular exam board's desires. It should be said after much modification and a pretty successful harvest of aspirin, the biology teacher who supervised the class slowly began to realise when we were discussing melting points that aspirin and paracetamol may not be the same thing and he may have ordered an entirely wrong practical... Suffice to say I, the chemistry teacher and the students have yet to allow him to live it down. On the other hand, we are the habit of getting them to do both aspirin and paracetamol over two years (BTEC), so they won't be too badly off for it.

1. Weigh a 50ml conical flask.
2. Place 1g Salycillic acid in the flask and weigh again. Add 5.0 mL of acetic anhydride into the flask. Add 5 drops of 85% phosphoric acid (catalyst) to the flask.
3. Place the flask in a beaker of hot water. Stir if needed to dissolve the salicylic acid. Keep the flask in the hot water bath for 10 more minutes.
4. While the flask is still in the water bath, slowly add 2 mL of distilled water to the flask to decompose any excess acetic anhydride.
5. After a minute, remove the flask from the water bath and add 20 mL of distilled water. Let the flask cool to room temperature. As the solution cools, crystals of aspirin will appear. Cool the solution further by placing the reaction flask in an ice bath. Chill a bottle of distilled water in a separate container.
6. Set up a Büchner funnel on a vacuum flask. Place the filter paper in the funnel and moisten with distilled water from a squirt bottle. Turn on the vacuum and transfer the aspirin slurry into the funnel. Wash the crystals with 5 mL of the cold DI water.
7. Transfer the aspirin into a clean 100ml flask and add 20ml ethanol. Redissolve the aspirin, using heat if necessary.
8. Allow the aspirin to cool in an icy bath and once again, crystals will appear.
9. Set up a funnel for gravity filtration.
10. Weigh a filter paper.
11. Filter the aspirin under gravity, leaving the setup until next lesson, when you will reweigh.

Not step 11 was just because of the exam board's desire to see some gravity filtration, it would normally be vacuum filtration.
 
Thanks technewham, we have to follow the OCR exam board method as described by 007. The one you have does work but not what they want. Who are we to suggest otherwise?? :eek::eek:
 
Hi Toni.

My chemists followed the porcedure below and the filter paper didn't dissolve, the key is to use COLD glacial, so I put the bottle in an ice water bath.

View attachment 1534
I remember doing this at my previous school and exactly the same thing happened - the filter papers dissolved when they added the glacial acetic acid. So I trialled it using ice cold distilled water instead as the method says all the glacial acetic is for is diluting the reaction mixture. It still worked so that's what we did instead after that. :)
 
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