Observation Exercise Based On Organic Chemistry

You are provided with three organic compounds H, I and J. H, I and J each belong to different homologous series. Carry out the reactions below and record your observations. In each case make what deductions you can about the functional group in the compound under test.

1.In a fume cupboard. Lace 3 drops of H on a piece of broken pot or a crucible lid and try to ignite it with a wooden splint.

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Observation

Inference

The splint ignites, and all of H is burned, leaving no excess liquid, but a yellow mark no the crucible lid.

There are double bonds present, which shows that solution H is unsaturated therefore H could be an alkene.

2.Place 1cm3 of H in a test tube, add equal volume of bromine water, cork the tube and shake the mixture.

Observation

Inference

There was a colour change from orange to yellow, decolourisation. There was a layer of bubbles with a layer of an oily liquid and a layer of a light yellow liquid.

This shows that the substance is an organic compound this is because it did not mix, which shows that it in an unsaturated hydrocarbon, again which gives the possibility that it may be an alkene

3. Place 1cm3 of H in a tube and add 1cm3 of dilute sulphuric acid and 10 drops of dilute potassium mangante (VII) solution. Shake the mixture.

Observation

Inference

There was a colour change from purple to brown, when the potassium mangante dissolved with the acid, but H sits on the top.

This in an oxidation reaction -Unsaturated hydrocarbon.

4. In a fume cupboard. Place 3 drops of I on a piece of broken pot or a crucible lid and try to ignite it with a wooden splint.

Observation

Inference

The flame was of a faint blue colour, there was no soot produced and there was a strong smell present.

Saturated hydrocarbon

5. Place 1cm3 of I in a tube and add 1cm3 of dilute sulphuric acid and 10 drops of potassium manganate (VII) solution. Heat the mixture using a water bath.

Observation

Inference

The solution went cloudy when sulphuric acid was added, and orangey brown when potassium added. When heated the orange colour disappears- Decolourisation

Potassium manganate is an oxidising agent, and the solution turns almost clear on heating, this shows that a reducing agent is also present. Oxidation has taken place. Therefore OH- is present.

6. Repeat test 5 with potassium dichromate (VI) in place of the potassium manganate (VII) solution.

Observation

Inference

At the first the colour changes to orange and then green. Whilst this happens an alcoholic smell is given off.

This shows the process of oxidation. As the colour of the solution changes twice, this could mean that the substance is a primary alcohol because this alcohol is able to oxidise to an aldehyde and then to a carboxylic acid. This therefore indicates it is part of the OH- group.

7. In a fume cupboard/ place 3 drops of J on a piece of broken pot or crucible lid and try to ignite it with a wooden splint.

Observation

Inference

An orange flame is produced. There is no residue and no soot given off.

There are saturated binds present, therefore single bond, that could suggest that it is an alkane

8. Place 1cm3 of J in a test tube, add an equal volume of bromine water, cork the tube and shake the mixture.

Observation

Inference

After shaking the mixture, a red layer if formed at the top of the solution and a pale yellow underneath. Underneath is the organic compound and on top sits the bromine water.

No double bonds present. It could be a hydrocarbon or an ester.

9. Place 1cm3 of J in a tube add an equal volume of dilute sulphuric acid and 10 drops of dilute potassium manganate (VII) solution. Shake the mixture.

Observation

Inference

There is a dark layer at the bottom and a layer of clear organic compound on top.

This shows that the substance is not a reducing agent and has saturated hydrocarbons. Highly saturated aliphatic hydrocarbon.

Formulae of:

H= alkene

I= primary alcohol

J=alkane

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