Identification of an Unknown Organic Compound Practicum


YOUR UNKNOWN  MAY HAVE ANY COMBINATION OF:


            . Saturated or unsaturated groups

            . Halide(s)

            . Alcohols


YOU WILL DETERMINE THE NAME OF YOUR COMPOUND BASED UPON ITS' BOILING/MELTING RANGE, AND CHEMICAL CLASSIFICATION TESTS

Alkyl Halide Classification Tests


ALCOHOLIC SILVER NITRATE TEST:

Add 1 drop of liquid, or a tiny amount of solid sample to 20 drops of a 0.1M solution of silver nitrate in 95% ethanol.

If no reaction is observed within five minutes at room temperature, warm the mixture in a beaker of boiling water (using your hot plate and adding boiling chips to the bath), and observe any change.

Note the color of any precipitates; silver chloride is white, silver bromide is pale yellow, and silver iodide is yellow.

If there is any precipitate, add several drops of 1M nitric acid solution to it, and note any changes; the silver halides are insoluble in acid.

Dispose of test tube contents into the Silver Recovery bottle.

            Failure to do so will result in a 2 point deduction from your practicum score


Record observations and conclusions in the Results portion of your lab report


SODIUM IODIDE IN ACETONE TEST:

Place 20 drops of the sodium iodide in acetone test solution in a test tube, and add 2 drops of liquid or a small amount of solid unknown.  Cover and shake the test tube.

Allow the tube to stand for 3 minutes and observe the formation of any precipitate.

If no precipitate has formed, heat the tube in a bath of 50oC water (hot plate) for 6 minutes, then allow it to cool to room temperature.

If a precipitate has formed, shake the contents of the tube.

If the precipitate is still present after shaking the test tube and allowing it to stand at room temperature for 3 minutes, the test is positive.

Note in all cases the differences in reactivity as evidenced by the rate of formation of sodium bromide, chloride, or iodide.

Dispose of test tube contents into the Recovered Organic Solvents bottle.

            Failure to do so will result in a 2 point deduction from your practicum score


Record observations and conclusions in the Results portion of your lab report

Alkene Classification Test


THE BAER TEST:

Place one drop of your unknown in a clean depression of a white spot plate, and add 1 drop KMnO4. Stir the solution with a stirring rod and spot the solution onto a piece of filter paper.


Interpret your results based on your previous alkene test observations.

Dispose of the test tubes contents into the Recovered Organic Solvents bottle.

            Failure to do so will result in a 2 point deduction from your practcum score


 Record observations and conclusions in the Results portion of your lab report

Alcohol Classification Tests


Perform the following tests on the known primary, secondary and tertiary alcohols provided, and your unknown.

Primary and secondary alcohols give a positive test within 5 seconds.


CHROMIC ACID IN ACETONE TEST:


                                                                H2CrO4

Primary alcohols and aldehydes:  RCH2OH ------------> RCO2H


                                                                 H2CrO4              H2CrO4

Secondary alcohols and aldehydes:  R2CHOH ------------> R2CO -----*-----> no visible reaction

                                                                              Ketones do not react, BUT, Aldehydes do.

 

                                                           H2CrO4

Tertiary alcohols and aldehydes: R3COH -----*-----> no visible reaction


In a test tube add 1 drop of your unknown or 1 drop of a known alcohol and 20 drops of acetone.

Add 1 drop of chromic acid reagent, cork and shake the tube to mix the contents.  A positive reaction is indicated by the disappearance of orange color and formation of a green or blue-green precipitate.

Color changes occurring after one minute should not be construed as a positive test. (why ?).

Dispose of the contents of your test tubes into the "Recovered Organic Solvent" bottle.

            Failure to do so will result in a 2 point deduction from your practcum score


Record observations and conclusions in the Results portion of your Lab Report in tabular form as follows:


Compound Name

Chromic acid test results

Lucas test results


LUCAS TEST:


R3COH + HCl + Zn(Cl)2 ---> R3CCl + H2O


To each of 4 test tubes, add 8 drops of the primary, secondary, and tertiary known alcohols, and, your unknown, respectively.


Add 40 drops of Lucas reagent to each tube.  Stopper the tubes and shake.


Allow the tubes to stand at room temperature, noting the time required for the formation of an alkyl chloride, which will appear as an emulsion.


Pour the contents of the test tubes down the sink.


Return in the remainder of your Unknown to its’ container and leave the container at your lab bench.  Failure to do so will result in a 10 point deduction from your practcum score.