Identification of Unknown OrganicCompound

Carefully add a spatula of PCl5 bit by bit.

Keep product Dry

If positive, steamy white fumes will be given off.

Hydroxyl group present, could be Primary alcohol, Tertiary Alchohol, Phenol or Carboxylic acid

2

Ethanoic acid test

Test for all Alcohols

Pour 2cm3 of H into test tube; add equal volume of ethanoic acid. Add 10 drops of H2SO4 and the warm gently.

Pour mixture into 400ml beaker containing 200ml water.

A Sweet smell is given off

Alcohols present, could be primary or Tertiary. The Alchohol was oxidised to and ester.

3

Test for Primary Alchohols using Jones's reagent

(CrO3-H2SO4 in H2O)

In a test tube, place 1 ml of acetone in a test tube and dissolve one drop of the unknown compound

Add one drop of Jones's reagent and then shake the test tube to mix contents

Primary and secondary alcohols react within two seconds. There is colour change form orange to green or blue-green, product is a precipitate.

Primary alcohol is fully oxidised to acid,

No reaction for Tertiary Alchohol.

Primary Alchohol Present and Confirmed.

Label Test tube "Alchohols"

4

Test for Tertiary Alchohol using Lucas reagent

[ZnCl2 - conc. HCl]

To 1 ml of the unknown compound in a test tube add 6 mls of Lucas' reagent at room temperature. Close the tube with a cork, shake properly and then allow to stand.

Very fast reaction and droplets of alkyl chloride formed almost immediately

For Primary alcohols there is no reaction (except allyl alcohol - droplets which are formed after 7 minutes).

Therefore tertiary Alcohol is present and Confirmed.

Label test tube Tertiary Alchohol

5

Acid Test

pH of aqueous solution

Test the pH of the unknown compound using universal indicator

Carboxylic acid around pH 3-4

Phenol around pH 5-6

Phenol and carboxylic acids again confirmed present.

6

NaHCO3 Test

Acid test for carboxylic groups

Add a spatula of NaHCO3 to aqueous unknown compound

A gas is given off. Gas turns lime water milky, ( Gas given off is CO2)

Carboxylic acid present and confirmed as this test is negative for Phenols and Alchohols.

Label Test tube Carboxylic Acid

7

FeCl3 Test

This is the test for Phenols

Dissolve 0.50g of unknown compound in water, add aqueous solution of iron(III) chloride drop-wise

There is colour change.

Violet colour for phenol,

Red colour for carboxylic acids

Phenol present and confirmed

Label Test tube Phenol

8

2,4-DNP test

This is a test for carbonyls ( Aldehydes and Ketones)

Add a few drops of a solution of 2,4-DNP t o the unknown compound

Label product Carbonyl

A yellow or orange precipitate is produced.

No Precipitate is produced with Carboxylic acid, phenol or esters.

Therefore carbonyls(Aldehyde and Ketone) present

9

Confirmation of Aldehyde using Tollens Reagent

Add 2 - 3 drops of the unknown compound in methanol to 2 - 3 mL of Tollen's reagent contained in a very clean test tube. Warm gently in a water bath.

A silver mirror forms on the side of the test tube from the colourless solution

Silver Ion is reduced to silver metal.

Reaction is negative with Ketone

Therefore Aldehyde Present and Confirmed.

Label test tube Aldehyde.

0

Confirmation of Presence of Ketone

Recrystallise the product labelled Carbonyl (from Test No. 8 ).

Determine its melting point, and then compare against a known ketone melting point

Positive Result,

Melting point matches that of a known ketone

Ketone present and Confirmed.

Label test tube as Ketone

1

Bromine Test

For Alkenes

To the unknown compound add bromine water drop-wise until the bromine colour remains

Bromine water is decolourised from brown to colourless

Phenol will form a white ppt with bromine water, but a colourless solution depicts presence of Alkenes.

Alkenes present and confirmed.

Label test tube as Alkenes

2

Hydroxamic acid test for Identifying esters

In a test tube, mix 1 drop of unknown compound with 1 ml of 0.5 mols hydroxylamine hydrochloride in 95% ethanol and add 0.2 ml of 6 mols aqueous sodium hydroxide. Heat the mixture until it boils. On cooling, add 2 ml of hydrochloric acid. If the solution is cloudy, add 2 mL of 95% ethanol. Add I drop of 5% iron (III) chloride. Observe colour change

A positive test will be a distinct burgundy or magenta colour

Esters react with hydroxylamine in the presence of sodium hydroxide to form the sodium salt of the corresponding hydroxamic acid. On acidification and addition of ferric chloride the magenta-coloured iron (III) complex of the hydroxamic acid is formed.

Therefore Ester is present and confirmed.

Flow Chart

Risk Analysis

Safety precautions

Alchohols - (Ethanol)

Causes skin and eye irritation

Highly flammable

Harmful by Inhalation

Avoid contact with skin and eyes. Wear eye protection; wash with cold water in the event of contact.

Avoid contact with open fire, take car while heating/refluxing, if possible use heating mantle instead of Bunsen burner.

Avoid Inhaling gas

Ester

May act as Irritant

Wear safety glasses

Ensure there is adequate ventilation

H2SO4

Corrosive

Liquid can cause damage to skin and eyes

See safety precautions on alchohols

Use gloves

PCl5

Corrosive

Always use the fume cupboard

Tollens Reagent

Highly explosive

After the test with Tollens reagent, pour the contents of the test tube into a sink and wash the test tube with dilute nitric acid. Any silver fulminate present, which is highly explosive when dry, will be destroyed

* Proper care should be taken when handling glass wares

References

Here are some resources that I used for this coursework.

Make the Grades Chemistry

By George Facer

ISBN 0-7487-7281-2

Page 37

OCR Chemistry 2

ISBN 0-521-79882-5

Pages 7,16,21-31 &50

http://www.chem.missouri.edu/Chem2140/Identification%20of%20Unknown%20Organic%20Compounds.doc

http://www.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/alcohol.html

www.mrsvillegas.com/labs/identifying_organic_compounds.pdf

http://www.chemguide.co.uk/organicprops/alcohols/oxidation.html

Christian Nwaigwe Jnr