Qualitative Analysis For Organic Compounds

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Hydroxamic Acid Test

Back 1

This test is used mainly to detect the presence of an ester function, but it can be modified to test for amides and nitriles.

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Ceric Ammonium Nitrate

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General test for alcohols
Almost all alcohols form an immediate red complex with the reagent, but the color disappears after a period of time that depends on the type of alcohol.
This test is not designed for phenols.

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Chromic Anhydride Oxidation

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Jones Test.
It is used mainly to differentiate btw aldehydes and ketones. It can also serve as a sub-classification test for alcohols since 1o and 2o alcohols react but 3o alcohols do not.
Alcohols usually react within 2 to 4 sec and produce a color change from orange to green or blue-green.
Aldehydes are slower and may require 20 to 30 sec, but the color change tends toward dark olive green rather that blue-green.

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Lucas Test

Back 4

This is a sub-classification test for alcohols.
Remember the unknown must be soluble in the reagent.
Sn1

Front 5

Iodoform Test

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This is a sub-classification test for methyl ketones and 2o alcohols with a methyl group on the carbinol carbon.

Front 6

2,4-Dinitrophenylhydrazine Test

Back 6

The 2,4-DNP reacts with aldehydes and ketones to give an orange or red-orange precipitate.
There are few ketones that five liquid rather than solid 2,4-dinitrophenylhydrazones and a few highly hindered ketones fail to react.

Front 7

Hydroxylamine Hydrochloride Test

Back 7

It is a redundant test for aldehydes and ketones.

Front 8

Sodium Bisulfite Addition Complex

Back 8

It provides a positive test for aldehydes and low molecular weight methyl ketones.

Front 9

Tollens Test

Back 9

This test was developed for use in carbohydrate chemistry to detect reducing sugars. Be

Front 10

Benzenesulfonyl chloride

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Hinsberg Test
This is a sub-classification test for amines. Tertiary amines do not react, but 1o and 2o amines produce benzenesulfonamide derivatives. The benzensulfonamide derivative of a 1o amine is soluble in 10% NaOH, so the precipitate does not form until the rxn mixture is acidified in the last step.

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Nitrous Acid

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This test is not particularly useful except for 1o amines. If the 1o amine is aromatic, the diazonium salt is stable at 0 oC in an ice bath. The presence of an aromatic diazonium salt can be determined by the coupling rxn with the sodium salt of 2-naphtol which produces a red or orange azo dye. If the 1o amine is aliphatic, the resulting diazonum salt is unstable even at 0 oC and decomposes by the vigorous evolution of N2 gas.

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Nickel Chloride Test

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This test is for primary amines. A small of precipitate may be positive but is probably not to be trusted.

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Ninhydrin Test

Back 13

Ninhydrin reacts with most alpha and beta aminoacids to produce a blue or bluish-red dye.
Proline and hydroxyproline are exceptions and give a yellow precipitate instead.

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Borax Test

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This test detects 1,2-diols, vicinal polyols, and carbohydrates but is not totally reliable.

Front 15

Periodic Acid Oxidation

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This test is positive for a variety of vicinal oxygen functions.

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Benedict's Solution

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It is a sub-classification test used to detect reducing sugars. It gives exactly the same information as the Tollens test.

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Fehling's solution

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It gives exactly the same information as the Benedict's and Tollens test.

Front 18

Silver Nitrate Solution

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It is useful only as a sub-classification test for alkyl chlorides and alkyl bromides.
The mechanism for the reactions is SN1 and a positive test is the formation of a precipitate (AgCl or AgBr).

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Sodium Iodide in Acetone Test

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This is also a sub-classification test for alkyl chlorides and alkyl bromides, but the mechanism is SN2.

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Bromine Solution

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Test for unsaturation.
A positive test is the loss of color as bromine is consumed. Be aware that ketones, phenols, and aromatic amines may also react to discharge the bromine color, but these reactions are also accompanied by evolution of HBr (the reaction is substitution and not addition).

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Potassium Permanganate Solution

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Baeyer unsaturation test
The observations for a positive test are the disappearance of the purple color and the formation of a brown precipitate.
Primary and secondary alcohol unknowns may give a false positive test due to oxidation of the carbonill group. Likewise, phenols, aldehydes, aromatic amines, and other compounds that are easily oxidized may react as well.

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Silver Nitrate Solution

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It is useful only as a sub-classification test for alkyl chlorides and alkyl bromides.
The mechanism for the reactions is SN1 and a positive test is the formation of a precipitate (AgCl or AgBr).

Front 23

Sodium Iodide in Acetone Test

Back 23

This is also a sub-classification test for alkyl chlorides and alkyl bromides, but the mechanism is SN2.

Front 24

Bromine Solution

Back 24

Test for unsaturation.
A positive test is the loss of color as bromine is consumed. Be aware that ketones, phenols, and aromatic amines may also react to discharge the bromine color, but these reactions are also accompanied by evolution of HBr (the reaction is substitution and not addition).

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Potassium Permanganate Solution

Back 25

Baeyer unsaturation test
The observations for a positive test are the disappearance of the purple color and the formation of a brown precipitate.
Primary and secondary alcohol unknowns may give a false positive test due to oxidation of the carbonill group. Likewise, phenols, aldehydes, aromatic amines, and other compounds that are easily oxidized may react as well.

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chloroform and aluminum chloride

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The generation of any color other than yellow is a positive indication for the presence of an aromatic ring of some sort.

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Ferrous Hydroxyde Reduction

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This is a test for nitro groups that use ferrous ion as a reducing agent.
Ex. Nitrobenzene gives a strong positive test (red-brown).

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Treatment of Aromatic Nitro Compounds with Sodium Hydroxide

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This experiment detects the presence of more than one nitro group on an aromatic ring by the intense colors of the Meisenheimer complexes produced.

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Ferric Chloride-Pyridine reagent

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This is a test for enols and phenols.