8/2/2019 3D1CC766213F428C812619271266227D

1/3

Experiment # 8

Synthesis and Reactivity oftert-Butyl ChlorideIntroduction:

The purpose of this experiment is to synthesize tert-butyl chloride via an SN1

reaction and to characterize it using simple chemical tests to describe its reactivity.

HCl

tert-butyl alcohol tert-butyl chloride

OH Cl

Tertiary alcohols can easily be converted to their corresponding alkyl chlorides by

the addition of concentrated hydrochloric acid to the alcohol. In this experiment,

concentrated hydrochloric acid is used to prepare tert-butyl chloride from tert-butylalcohol via SN1 reaction.

The mechanism of this SN1 reaction involves three steps. First, is the rapid (and

reversible) protonation of the alcohol, followed by the much slower rate-determiningstep, the loss of water to give a relatively stable tertiary carbocation. In the final step, the

carbocation is rapidly attacked by the chloride ion to form the alkyl halide. The alkyl

halide is insoluble in water, and thus it separates from the aqueous layer.

OH OH2 ClH-Cl -H2O Cl

Characterization of alkyl halides takes advantage of the fact that the halogen caneasily be displaced. The two tests that you will use are complementary, and are useful for

classifying the structure of alkyl halides. The silver nitrate test proceeds via an SN1

reaction, and the sodium iodide test proceeds via an SN2 reaction.When a halide is treated with a solution of AgNO3 in ethanol, the silver ion

initially coordinates with the halogen electron pair. This in turn weakens the carbon

halogen bond, and a molecule of insoluble silver halide is formed. The resulting

carbocation reacts with the ethanol to form an ethyl ether. Since this reaction is an S N1reaction, the order of reactivity for this test tertiary > secondary > primary > methyl.

The sodium iodide test is used to test for the presence of bromine or chlorine.Alkyl halides that can react by an SN2 mechanism to give a precipitate of sodium halidesalt. The order of reactivity of alkyl halides in this reaction is methyl > primary >

secondary > tertiary.

8/2/2019 3D1CC766213F428C812619271266227D

2/3

Procedure:

Part A: Synthesis oftert-butyl chlorideTo a 125 mL separatory funnel, carefully add 15 mL of concentrated acid and 5

mL oftert-butyl alcohol. Swirl the contents of the funnel, place the stopper on, and invert

it. Open the stopcock immediately to release excess pressure, pointing the funnel towardsthe back of the fumehood. Shake the funnel and vent at regular intervals. Place the funnelin a ring stand and allow the two layers to separate. Drain the lower aqueous layer into a

250 mL Erlenmeyer flask (labeled H2O to remind you that this is the aqueous layer). Add

40 mL of saturated sodium bicarbonate solution to the organic layer remaining in the

funnel. Gently swirl the funnel several times until the bubbling ceases. Then, stopper thefunnel, invert it, and vent immediately. Shake the funnel and vent it at regular intervals.

Place the funnel back in the ring stand and allow the two layers to separate. Drain the

lower aqueous layer in the Erlenmeyer flask. Wash the organic layer with 30 mL ofwater. Again, drain the lower aqueous layer into the Erlenmeyer flask. Transfer the

organic layer (the crude product, tert-butyl chloride) into a clean and dry 50 mL

Erlenmeyer flask and dry using calcium chloride. Decant or pipet off the liquid into a pre-weighed 10 mL beaker. Get the weight of your crude product, and calculate the percent

yield (the tert-butyl alcohol is your limiting reagent).

Part B: Qualitative Chemical Tests for Reactivity

Obtain a test tube rack, and label the four small test tubes. Into two tubes add a

couple drops of your synthesized tert-butyl chloride. Into the other two test tubes add acouple drops of 1-chlorobutane. To one test tube of each compound add 1 mL of sodium

iodide solution, stopper the test tube, and shake the contents vigorously. Note the time ittakes for any precipitate to form (at the first appearance of any precipitate). To the other

two test tubes, add 1 mL of the silver nitrate solution, stopper the test tube, and shake the

contents vigorously.Avoid getting the AgNO3 solution on your skin! Again, note the timeit takes for any precipitate to form (at the first appearance of any precipitate).

8/2/2019 3D1CC766213F428C812619271266227D

3/3

Equipment:Each pair will obtain the following glassware/equipment from the cart at the front of the

room before starting the experiment. All equipment should be cleaned and returned to the

cart before leaving the lab.- 1 125 mL separatory funnel with stopper-

1 250 mL erlenmeyer flask- 1 50 mL erlenmeyer flask- 1 10 mL beaker- 1 test tube rack with 4 test tubes and stoppers- 1 pipet bulb- 1 10 mL graduated cylinder- 1 50 mL graduated cylinder

Glass pipets will be on the bench tops. All chemicals will be in the fume hood. There will

be a ring stand in each fumehood. All aqueous waste can be washed down the drain with

water. Organic liquid waste should go into the waste container that will be in thefumehood.

Safety Considerations:- Take care when using the concentrated acid and the silver nitrate solution to not

get it on your skin or clothing. Since we are using a larger volume of concentrated

acid this week, you may want to choose what you wear to lab carefully!

- There will be a waste container for organic liquid waste- Dispose of used glass pipets in the broken glass container