experiment 12: the dehydration of cyclohexanol

most to least dense

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

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

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