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Introduction

The Planning Exercise To Identify Some Organic Compounds Containing Oxygen In this practical I will try to identify some unknown organic compounds using chemical tests. The compounds tested are known to have three carbon atoms, six or eight hydrogen atoms, one or two oxygen atoms, and no atoms of any other elements. We also need to make sure that the compounds can only be alcohols, carbonyl compounds, carboxylic acids or esters. Six different compounds that follow the above criteria are used, and these are propan-1-ol, propan-2-ol, propanal, propanone, propanoic acid, and methyl ethanoate. An aldehyde, propanal, can be identified by first a positive test with 2,4-dinitrophenylhydrazine, showing it is a carbonyl compound and nothing else, where the solution would turn yellow, then a positive test with Tollen's Reagent, where a 'silver mirror' would be formed, showing that the compound can be oxidise. A ketone, propanone, can be identified by first a positive test with 2,4-dinitrophenylhydrazine, showing it is a carbonyl compound and nothing else, where ...read more.

Middle

The solution is distilled from the acidified potassium dichromate, and then is tested negatively with universal indicator paper, which don't change colour, showing the absence of acid, and thus can only be a ketone, meaning the original compound is a secondary alcohol. An ester, methyl ethanoate, can be identified by first a negative test with 2,4-dinitrophenylhydrazine, showing it is not a carbonyl compound, then a negative test with acidified potassium dichromate, where the solution do not change colour, showing it can not be oxidised, as it can only be propanoic acid or methyl ethanoate, then a negative test with sodium carbonate in which no gas is produced, shows that it is methyl ethanoate. Apparatus 1 test tube rack, 7 test tubes, 1 pipette, 1 distilling column, 1 beaker, 1 small conical flask, 1 Bunsen burner, 6 unknown organic solutions, 1 safety spectacles, 1 heat proof mat, 1 gauze, 1 tripod, solution of 2,4-dinitrophenylhydrazine, universal indicator paper, solution of Tollen's Reagent, solution of acidified potassium dichromate, solution of sodium carbonate. ...read more.

Conclusion

Analysis of observations obtained Test Unknown organic compound 2,4-dinitrophenylhydrazine Tollen's Reagent Potassium dichromate Sodium carbonate Solution turns yellow Silver mirror Solution turns green, makes universal indicator paper red No reaction Propanal Solution turns yellow No reaction No reaction No reaction Propanone No reaction No reaction No reaction Gas is produced Propanoic acid No reaction Silver mirror Solution turns green, makes universal indicator paper red No reaction Propan-1-ol No reaction Silver mirror Solution turns green, universal indicator paper turns green No reaction Propan-2-ol No reaction No reaction No reaction No reaction Methyl ethanoate Safety precautions and risk assessments Some of the chemicals used are irritant if not corrosive, therefore safety spectacles must be worn at all time during the practical investigation. At no point of the experiment should the person be sitting down, this is because hot water and fire is being used, and being sated would make escape slower. As all of the organic compounds used are extremely flammable, do not let the compounds near naked flame, and be very careful during heating, must use a hot water bath as a medium for heating. ...read more.

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