[Big_Joe]

As part of a piece of a piece of coursework i must plan an experiment to find out about an unknown chemical. I've come up with a plan for this and would just like someone experienced to check it for any errors it may contain. The chemical can be one of the following: an alkene, primary alcohol, secondary alcohol, tertiary alcohol, aldehyde, ketone, carboxylic acid, ester or a phenol.
The tests must also depend upon the consequence of the previous.

1. Firstly i propose adding bromine water to the chemical. If the bromine water turns colorless in the solution with no precipitate then the chemical is either an alkene. If it produces a white precipitate then it is a phenol.

2. Secondly to test if it is an aldehyde or ketone, the original chemical should be reacted by adding 2,4-dinitrophenylhydrazine reagent to the chemical and shaken up. If a precipitate is formed then it is an aldehyde or ketone. If the result is positive then in order to distinguish whether it is an aldehyde or ketone, it should be tested by adding tollens reagent to the original solution with a few drops of concentrated ammonia and then heated gently and diluted with water. If a sliver mirror/black precipitate is formed then it is an aldehyde. If it is not formed then the chemical must be a ketone.

3. If all the previous tests have been negative then it must be either a primary, secondary or tertiary alcohol, an ester or a carboxylic acid. To test if it is a primary or secondary alchohol, it could be oxidised with acidified potassium dichromate solution and concentrated sulfuric acid. If an oxidation reaction occurs the colour of the solution will turn from orange to green which indicates it is either a primary or secondary alcohol. To distinguish which of these it is, the oxidised solution could be added to phosphorus pentachloride. If carbon dioxide gas was produced (which could be tested using limewater), then the oxidised solution was a carboxylic acid meaning the origional solution was a primary alchohol, if it did not react then the oxidised solution must have been a ketone which means the origional was a secondary alchohol.

4. This leaves me with just an ester, tertiary alchohol and a carboxylic acid. Since a tertiary alchohol will react with PCl5 i cannot use this test for the carboxylic acid. In order to test to see if it is an ester i could simply use universal indicator or litmus red to see if it acidic. If it is then it must be a carboxylic acid since the others are not acidic.

5. To finally decide if it is a tertiary alcohol or ester i could test it the only thing i could think of would be to do a complex reaction trying to react it with saturated ethanolic hydroxylamine hydrochloride to see if it is an ester. If it isn't an ester it must be a tertiary alcohol.

Can people please give me some feedback on this and tell me if i have made any errors in my planning and if anyone knows a simple chemical test i could use to distinguish between a tertiary alcohol and an ester please say!

I would ideally want some feedback by tommorow so i can complete it over the next few days.

Thanks in advance

[CopperSmurf]

I hope this isn't too late. Your steps looks and sounds ok to me, but in the very very beginning, you really should test for solubility, like 0.03g of unknown + 1 mL of liquid. Like, first try in water, then some in a strong base, some in strong acid, weak base/acid, etc. to get an idea if you got a multifunctional compound and whether it has a base or acid group.

I personally like to use Luca's Reagent to find out about 1 or 2 degree or tertiary alcohol, if you're allowed to have that. It's just ZnCl2 in HCl.

As for esters, generally they are very unreactive and you can sometimes get a hint of an ester by its smell. If all of the above don't work, then your only choice left is an ester.