Experiment 12: The Dehydration of Cyclohexanol

Which of the following is used for the treatment of reagent spills in the laboratory:

sodium bicarbonate; boric acid; sodium thiosulfate; water

why is the reaction of cyclohexene with HBr (a rapid, simple reaction) not useful as a characterization reaction?

-HBr would not show color change so therefore you would not be able to see if there is a double bond present

the permanganate test (Baeyer's)

-With alkenes and alkynes, the deep purple color disappears, and a brown precipitate of manganese dioxide is formed.

why would concentrated HCl be a poor choice as the acid catalyst for the formation of cyclohexene by dehydration of cyclohexanol?

-because the chlorine ion would attack the carbocation to form a bond -a double bond would not form

true statements about Br2

-causes skin burns -may be fatal if inhaled -gloves must be worn while handling it -Br2 is NOT a reducing agent

the experiment states that a distillation should never be continued until the distilling flask is dry. does a dry mean "no water present" as when using drying agent on an organic solution?

-it means that there should be nothing in the flask at all whether that be water or something else

azeotropes

-mixture of two liquids that has a single sharp boiling point -mixtures of three and four compounds form azeotropes -you cant separate them by distillation -you cannot state unknown liquid that boils at constant temp is pure

if concentrated acid is spilled during the experiment what is the proper procedure for cleaning the spill?

-neutralize the spill with sodium bicarbonate

bromine test

-positive test, the bromine color is discharged rapidly without the evolution of hydrogen bromide.

appropriate response if skin comes in contact with HCl

-student should tell TA immediately and wash their hands/skin copious amounts of water in sink

indicate how you determined whether reaction had occurred

-the product separated forming layers -top layer was cyclohexene and bottom layer was aqueous layer

in order to perform the bromine test on a compound it must be treated with a dilute solution of bromine. which of the following results will indicate the presence of an alkane?

-the reddish color of the bromine will disappear

the reactions of bromine and of permanganate with cyclohexene both belong to which of the four general kinds of reaction?

-they both react by addition -the double bond will be broken and the bromine will attach

Acetone is not suitable as a solvent for extraction of organic materials from water because:

Acetone and water are miscible.

What is the similarity with E2 elimination and SN2 substitution?

Concentration of nucleophile affects the rate of the reactions

The reaction performed in the dehydrohalogenation experiment was an E2 reaction. Which of the following statements about E2 reactions are true?

E2 reactions are stereospecific; Strong bases encourage elimination reactions; It is easier to perform an E2 reaction on an alkyl chloride than an alkyl fluoride; Tertiary alkyl halides will undergo faster elimination than secondary alkyl halides

reaction is..

In the first step the -OH is protonated to form a protonated alcohol. See Figure below. The protonated alcohol now contains a much better leaving group, a water molecule. In the second step of the reaction (Dehydration), the protonated alcohol loses water to form a carbocation. The rate of this slow step determines the overall rate of this reaction. The loss of a proton from the carbocation is rapid.

purpose

In this experiment, cyclohexanol will be dehydrated (acid catalyzed) to form cyclohexene in an elimination reaction. Water is eliminated to form a carbon-carbon π-bond -this is an E1 reaction

Which of the following is true about the formation of 3‐chloro‐3,7‐dimethyloctane from 3,7‐ dimethyl‐3‐octanol?

The alcohol is protonated and a water molecule is produced in the reaction.

In the dehydration of cyclohexanol experiment, the reaction undergoes through a carbocation intermediate (E1 mechanism). Which of the following three steps (I‐III) is the rate‐determining step (RDS) of the reaction?

The rate of the formation of the carbocation when the protonated alcohol loses the water is the RDS (dehydration)

What should you do if you spill sulfuric acid on your hand?

Wash it with cold water and apply 0.6 M sodium bicarbonate solution.

most to least dense

most : chloroform > dichloromethane > water > diethyl ether > hexanes

If you spill sulfuric acid on your hand, after rinsing with water you should rinse the area with a solution of:

sodium bicarbonate