Sodium Iodide in Acetone Test

Standards
Reference tests done in Classification Tests for Halides Lab

Procedure
In a test tube place 0.25 mL or 0.2 g of your unknown. Add 2 mL of a 15% solution of sodium iodide in acetone, noting the time of addition. After the addition, shake the test tube well to ensure adequate mixing of the unknown and the solution. Record the time needed for any precipitate to form. After about 5 minutes, if no precipitate forms, place the test tube in a 50oC water bath. Be careful not to allow the temperature of the water bath to go above this temperature since the acetone will evaporate, giving a false positive result. After 6 minutes more in the bath, if no precipitates are visible, remove the test tube and let it cool to room temperature. Note any change that might indicate that a reaction has occurred. Continue slow reactions for up to 45 minutes at room temperature.

Positive Test
The formation of a white precipitate indicates the presence of halides.

Complications
When the sodium iodide solution is added to the unknown, a precipitate of sodium iodide might occur leading to a false positive test. Upon mixing, the precipitate of sodium iodide should dissolve.

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Silver Nitrate in Ethanol Test

Standards, as done in the Classification Tests for Halides lab


1-chlorobutane 1-bromobutane 1-iodobutane
2-chlorobutane 2-bromobutane 2-iodobutane
2-chloro-2-methylpropane 2-bromo-2-methylpropane
benzyl chloride bromobenzene


Procedure
Place approximately 0.25 mL of each compound into a test tube. Add 2 mL of a 1% ethanolic silver nitrate solution to the material in each test tube, noting the time of addition. After the addition, shake the test tube well to ensure adequate mixing of the compound and the solution. Record the time required for any precipitates to form. If no precipitates are seen after 5 minutes, heat the solution on the steam bath for approximately 5 minutes. Note whether a precipitate forms in the test tube. Continue slow reactions for up to 45 minutes at room temperature.

Complications
Carboxylic acids have been known to react in this test, giving false positives.

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Lucas Test for Secondary and Tertiary Alcohols

Standards
1-Butanol, 2-Butanol, t-Butyl alcohol.

Procedures
To 0.2 mL or 0.2 g of the unknown in a test tube add 2 mL of the Lucas reagent at room temperature. Stopper the tube and shake vigorously, then allow the mixture to stand. Note the time required for the formation of the alkyl chloride, which appears as an insoluble layer or emulsion.
The Lucas reagent is already prepared for you.

Positive test
Appearance of a cloudy second layer or emulsion

3o alcohols: immediate to 2-3 minutes
2o alcohols: 5 -10 minutes
1o alcohols: no reaction

Complications
The test applies only to those alcohols soluble in the reagent (monofunctional alcohols lower than hexyl and some polyfunctional alcohols.) This often means that alcohols with more than six carbon atoms cannot be tested.

Cleaning Up
Place all solutions in the appropriate waste container.

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Jones Oxidation for Primary and Secondary Alcohols

Standards
1-Butanol, 2-Butanol, t-Butyl alcohol

Procedure
Dissolve 10 mg or 2 drops of the unknown in 1 mL of pure acetone in a test tube and add to the solution 1 small drop of Jones reagent (chronic acid in sulfuric acid). A positive test is marked by the formation of a green color within 15 seconds upon addition of the orange-yellow reagent to a primary or secondary alcohol. Aldehydes also give a positive test, but tertiary alcohols do not.
The Jones reagent will already be prepared for you.

Positive Test
A positive test for aldehydes and primary or secondary alcohols consists in the production of an opaque suspension with a green to blue color. Tertiary alcohols give no visible reaction within 2 seconds, the solution remaining orange in color. Disregard any changes after 15 seconds.

Complications

Enols may give a positive test.
Phenols give a dark colored solution which is not blue-green like a positive test.
Cleaning up
Place all solutions in the appropriate waste container

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Iodoform Test for Methyl Ketones

Standard
Acetone

Procedure
If the substance to be tested is water soluble, dissolve 4 drops of a liquid or an estimated 50 mg of a solid in 2 mL of water in a large test tube. Add 2 mL of 3 M sodium hydroxide and then slowly add 3 mL of the iodine solution. Stopper the test tube and shake vigorously. A positive test will result in the brown color of the reagent disappearing and the yellow iodoform solid precipitating out of solution. If the substance to be tested is insoluble in water, dissolve it in 2 mL of 1,2-dimethoxyethane, proceed as above, and at the end dilute with 10 mL of water.

Positive Test
Formation of solid iodoform (yellow) is a positive test. (Iodoform can be recognized by its odor and yellow color and, more securely, from the melting point 119o-123oC).

Complications
Test will not be positive if the R group is a di-ortho substituted aryl group

Cleaning Up
Place solutions in the appropriate waste container.

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