Chemistry, Distinguish between chemicals.

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MedicProspective
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Please excuse my idoicity on this one. I am going round and round in circles and need some help. The question is as follows:

You have four reagent bottles but the labels have been removed. You know that the reagents in the bottles are but-2-en-1-al, butanal, butanone and cyclohexene.

Write a plan, using chemicals tests, to distnuish between these four compounds.

You should only plan to include the minimum number of tests so that the chemicals are not used unnecessarily.

Now, my first thought was that it could be a simple test of using Bromine Water and then some Tollens' Reagent in order to figure out the compounds. However, this would not work as Bromine water could add across the C=O double bond in the aldehydes and the ketones. Part of me then considered doing 3 or 4 tests

First using 2,4-DNP to form the orange precipitates. This should eliminate the cyclohexene as it would form the required crystals due to the nature of there being no C=O double bond. Then you can heat small amounts using acidified potassium dichromate. This would then eliminate the Butanone as the ketone cannot be oxidised further and would be shown by the lack of green Cr 3+ ions. Then, a Tollen's Reagents Test to ensure the correct 2 aldehydes are selected. Finally, using known boiling points, could you still out one of them using quickfit apparatus.

Please say if I have got anything wrong or if I have over stepped the margin.

Thanks for any advice in advance.
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MedicProspective
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(Original post by MedicProspective)
Please excuse my idoicity on this one. I am going round and round in circles and need some help. The question is as follows:

You have four reagent bottles but the labels have been removed. You know that the reagents in the bottles are but-2-en-1-al, butanal, butanone and cyclohexene.

Write a plan, using chemicals tests, to distnuish between these four compounds.

You should only plan to include the minimum number of tests so that the chemicals are not used unnecessarily.

Now, my first thought was that it could be a simple test of using Bromine Water and then some Tollens' Reagent in order to figure out the compounds. However, this would not work as Bromine water could add across the C=O double bond in the aldehydes and the ketones. Part of me then considered doing 3 or 4 tests

First using 2,4-DNP to form the orange precipitates. This should eliminate the cyclohexene as it would form the required crystals due to the nature of there being no C=O double bond. Then you can heat small amounts using acidified potassium dichromate. This would then eliminate the Butanone as the ketone cannot be oxidised further and would be shown by the lack of green Cr 3+ ions. Then, a Tollen's Reagents Test to ensure the correct 2 aldehydes are selected. Finally, using known boiling points, could you still out one of them using quickfit apparatus.

Please say if I have got anything wrong or if I have over stepped the margin.

Thanks for any advice in advance.
Any guidance on this question would be useful. I have been stuck for the last few hours on this one.
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Fireworm21
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I would guess that you cant use boiling points as that should allow you to test each of them form the start and isnt really a chemical test.
between the aldehyde and the butenal I would use a soft nucleophile which would prefer to add 1-4 over 1-2, reacting selectively with the enone
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MedicProspective
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I thought of a boiling point test but thought it would not be a chemical test. It is hard as the OCR Textbook does not say anything about this, or how to determine between multiple ones. Unless if it were to be a 2,4-DNP crystal test and then find the boiling point of the crystal found by comparing to a table of known results for each species.
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Pigster
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(Original post by MedicProspective)
However, this would not work as Bromine water could add across the C=O double bond in the aldehydes and the ketones.
This reaction needs an acid/alkali as catalyst. Simply don't add one and you'd be fine to test for saturation with Br2(aq). Which level / spec are you studying?
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