Activity No. 2

Question 1

Cyclohexanol is a _______ alcohol that undergoes dehydration by what mechanism

Answer 1

secondary
E1 mechanism

Question 2

the key intermediate in the mechanism which can undergo substitution as well as elemination

Answer 2

a cyclohexyl cation

Question 3

how do you prepare an alkene in good yield

Answer 3

you must suppress the substitution reaction

Question 4

In this experiment the substitution reaction is suppressed by
(1)
(2)
(3)

Answer 4

(1) the use of strong acids w/anions that are relatively poor nucleophiles
(2) a high reaction temperature which favors elimination
(3) distillationof cyclohexene from the reaction mixture as it is formed

Question 5

TRUE/FALSE
Strong acid can be used as the dehydrating agent.

Answer 5

TRUE

Question 6

Strong acids that have been employed as dehydrating agent

Answer 6

Sulfuric acid
Phosphoric acid
Oxalic acid
and even Potassium hydrogen sulfate

Question 7

if the anions of an acid are all poor nucleophiles, what reaction is favored?

Answer 7

Elimination

Question 8

HBr have nucleophilic anions therefore thus it favors more to what reaction

Answer 8

Substitution

Question 9

This acid alone can cause both oxidation and polymerization of the product alkene

Answer 9

Concentrated sulfuric acid

Question 10

Fewer side reactions occur when this acid is used as the dehydrating agent, but the rate of the alkene formation is slow

Answer 10

concentrated phosphoric acid

Question 11

what is used as the dehydrating agent in this experiment

Answer 11

mixture of sulfuric and phosphoric acids

Question 12

Removal of the alkene is by _________ as it is being formed in the reaction mixture

Answer 12

distillation

Question 13

this is an excellent technique for preventing side reactions bht only applicable for dehydration reactions that produce low-boiling alkenes, such as cyclohexene

Answer 13

Distillation

Question 14

how do u reduce tar (polymer) formation

Answer 14

thru removal of the alkene

Question 15

removal of the alkene (reduces/increases) __________ formation by minimizing the contact between the acid and the alkene

Answer 15

reduces
tar (polymer)

Question 16

why is it that water was also removed from the acidic mixture in the distillation

Answer 16

to prevent the reverse reaction (reconversion of the cyclohexene to cyclohexanol) from occurring

Question 17

The distillate is an _______ of ___________ and ________

Answer 17

azeotrope
cyclohexene
water

Question 18

azeotrope of cyclohexene and water

Answer 18

90% cyclohexene
10% water
boiling pt. at 71°C

Question 19

TRUE/FALSE
Even with careful distillation, the cyclohexene-water distillate will still be contaminated w/ some cyclohexanol, which must be removed in the subsequent work-up

Answer 19

TRUE

Question 20

During the subsequent work up
The ________ is transferred to a separatory funnel and the aqueous layer is drawn off.

Answer 20

crude distillate

Question 21

Since cyclohexanol is slightly-water soluble, it is removed from the ________ by a _______.

Answer 21

crude cyclohexene
water extraction

Question 22

the cyclohexene is extracted with _________ solution as a preliminary drying step

Answer 22

saturated NaCl

Question 23

What drying agent is used in this experiment?

Answer 23

Anhydrous CaCl2

Question 24

Why is anhydrous CaCl2 is the drying agent of choice in this experiment

Answer 24

because it forms molecular complexes with alcohols, as well as with water,and thus removes the last traces of cyclohexanol

Question 25

After drying, the cyclohexene is purified by

Answer 25

distillation

Question 26

characteristic of phosphoric acid:

Answer 26

strong and corrosive

Question 27

What should u do if you have been splashed by any acid on ur skin or clothing

Answer 27

wash immediately with copious amount of water

Question 28

Characteristic of cyclohexene

Answer 28

Very volatile amd verry flammable

Question 29

cyclohexene must be stored in a __________ with a lightly, greased stopper

Answer 29

glass-stoppered bottle

Question 30

Its distillation should be carried out __________, w/ and efficient condenser, and into a flask that is well chilled in an ice bath

Answer 30

slowly

Question 31

TRUE/FLASE
Cyclohexene vapors are heavier than air, they will accumulate in the sink and drain

Answer 31

true

Question 32

Step 1 of the procedure

Answer 32

place 20 mL of cyclohexanol in a 100mL round-bottom flask. Then add 5mL of 85% phosphoric acid drop by drop. Swirl the mixture while adding the acid and then add 2-3 boiling chips

Question 33

2nd step

Answer 33

Immerse the flask in a water bath and equip for a simple distillation w/ a 125mL Erlenmeyer flask as the receiver. Heat gently up to 70°C for 15 minutes.

Question 34

Step 3

Answer 34

Continue heating gently and collect the distillate below 100°C. Towards the end of distilation, the residue turns yellow to dark brown. Stop the distillation if white fumes appear in the round bottom flask

Question 35

What must you do with the residue after distillation? (step 4)

Answer 35

simce the residue is a strong acid, it should be poured onto ice, diluted with water, and flushed down the drain w/ a generous amount of additional water

Question 36

what is the distillate

Answer 36

a mixture of water and crude cyclohexene

Question 37

Step 5t

Answer 37

transfer the distillate into a 125 mL separatory funnel

Question 38

Step 5

Answer 38

Transfer the distillate into a 125 mL separatory funnel

Question 39

Step 6

Answer 39

drain the aqueous layer (lower) then wash the cyclohexene remaining in the separatory funnel with 10 mL of water. Then drain the water layer (aqeuous layer)

Question 40

Step 7

Answer 40

Then wash it again with 10 mL of saturated NaCl solution

Question 41

Step 8

Answer 41

Finally, wash the cyclohexene with 10 mL of water. Amd because of the volatility of cyclohexene, all 3 washings (water, saturated NaCl soln, water) must be conducted quickly. Then discard the aqeuous layers in the sink when the extraction is completed

Question 42

Step 9

Answer 42

Drain the cyclohexene from the separatory funnel into a 50mL erlenmeyer flask. Then add 2 spatula-full of anhydrous calcium chloride and stopper the flask snugly. Allow the material to dry for atleast 20 minutes, w/ occasional swirling to hasten the drying

Question 43

Step 10

Answer 43

After drying, decant the bulk of cyclohexene into a pre-weighed covered bottle. Label and then obtain the weight of the product

Question 44

what must be followed in characterization process

Answer 44

perform bromine and Baeyer’s tests to cyclohexene and cyclohexanol