Note:  Commentaries are in color and placed in brackets.

Experiment 15: 


April 3, 1998 Afshin Farahi [date and signature]

Purpose: Cyclohexene will be prepared from cyclohexanol. The product will be isolated by simple
distillation. In addition, as a qualitative test for unsaturation, the reactivity of cyclohexene with KMNO4 and Br2 will observed.

Reaction Schemes:

Physical Properties: [obtain physical properties from Aldrich Catalog in
the reference section of the library]

Substance	mw	amount	mmol	mp(°C)	bp(°C)	density g/mL	Solubility water/organics
Cyclohexanol	100.2	1.3 mL	12	20-22	160-161	0.948	no/yes
Cyclohexene	82.2	-	-	-	83	0.810	no/yes
85% H3PO4	-	0.4 mL	-	-	-	-	yes/no
Conc. H2SO4	-	6 drops	-	-	-	-	yes/yes

[note: both H3PO4 and H2SO4 are catalysis and thus mmol used, mw, mp, and bp are not significant]

Safety Considerations: Both H3PO4 and H2SO4 are corrosive and should avoid contact with skin.
Bromine is highly corrosive and CCl4 is a suspect carcinogen; use only in fume hood and avoid
contact. 5% aqueous sodium thiosulfate should be used for treatment of bromine burns. [obtained
from text and lecture; see special instructions section for exp.]

Waste Disposal Considerations: Organic residues are to be discarded in the designated
nonhalogenated waste bottle. However, solutions remaining after the bromine test should be placed
in the halogenated waste bottle. The KMNO4 waste should be discarded in a bottle labeled heavy
metal waste. [obtained from text; see waste disposal section of exp.]

Procedure Outline: Apparatus Assembly 1. Place 1.3 mL of cyclohexanol w/plastic syringe & needle into a 5 mL conical vial 2. Add spin vane, 0.40 mL 85% H3PO4, 6 drops of conc. H2SO4 and mix thoroughly 3. Assemble distillation apparatus w/ air condenser (see figure 1). Do not charge with CaCl2 or any drying agent as suggested by text. figure 1 Dehydration 1. Place aluminum collar around the vial and heat mixture until it starts to distill. Regulate heat so that distillation takes 30-45 mins. 2. Remove distillate w/ Pasteur pipette (when necessary) into a dry 3 mL conical vial. Stop when there is no more liquid to distill (i.e., when liquid STOPS boiling). 3. After distillation, remove as much distillate as possible. Rinse sides of Hickman w/ ~1 mL of saturated aq. NaCl.   Isolation and Drying of Product 1. Allow layers to separate and remove bottom aq. layer 2. Transfer organic layer w/ Pasteur pipette into a small test tube w/ 2 microspatulafuls of granular anhydrous Na2SO4. 3. Stopper test tube and allow 5-10 mins for water removal. 4. This is a good time to wash and dry Hickman and 3 mL conical vial. Distillation 1. Transfer the dry liquid to a clean, dry 3 mL conical vial (leaving solid behind). 2. Add a boiling stone (and NOT spin vane) and assemble distillation apparatus (Figure 1). 3. Heat to 140-150 °C (or whatever temp. it takes to distill) 4. Collect and transfer distillate to a small tared vial with cap. 5. Weigh and calc. % yield. IR Spectrum Obtain IR spectrum of product. TA will DEMO operation. Unsaturation Test 1. Do in Hood. Place one drop of product into a test tube. Add ~0.50 mL CCl4/Br2 soln. and note any color changes. Text suggest to continue adding CCl4/Br2 soln. until color no longer discharge However, DO NOT do this. 2. Do the above procedure on the starting material, cyclohexanol. 3. Place 4-5 drops of product into another test tube. Add 0.3 mL of 1,2-dimethoxyethane and then add KMnO4 drop by drop until color is gone (will have ppt.). 4. Do the above procedure on the starting material, cyclohexanol.

Observations and variations:   cyclohexanol solidified in dispensing bottle; had to warm bottle in hot water bath                         Increased hotplate temp. to 180°C Distillation took 40 mins.       Used 1.5 mL of aq. NaCl soln.         Organic layer was cloudy   Dried 5 mins       Trace amount of solid transferred over     increased temp. to 180°C   tared vial = 20.982 g sample + vial = 21.340 g   obtained IR of sample on silver chloride plates     [place your observations for unsaturation tests here]

Results: [show all calculations]

Cyclohexanol is limiting reagent thus,

Cyclohexene isolated

mass cyclohexene = 21.340g-20.982g = 0.358 g

thus,

Experimental Yield

IR Data Table (neat): [in this example the IR spectrum is not included; however, you
need to include an IR spectrum of your compound]

 Wavenumber
      (cm-1)
 Assignment
 Comments
 

      
3024
2934
1662
718

      
=C­H unsaturated stretching
C­H saturated stretching
CH2 bending
=C­H out-of-plane bending

      
weak intensity

 
Concluding Comments:
[Generally, the conclusion should be brief and concise. The conclusion should focus on
sources of error, possible improvements either in technique or procedure. Comments on 
your % yield and the purity of your product. How did my %yield compare to the literature
(see your lecture text)? Why was a certain procedure used? E.g., Why was a saturated
solution of NaCl used? Were there any unexpected results?

Please do not take these above suggestions as your sole guideline for your conclusion.
The concluding comments should be your own and should cover those issues that you feel
are important to the experiment at hand. Finally, I strongly suggest that you browse
through scientific journals in the science library and use these examples as an additional
guide to help shape your laboratory write-ups.]

References:
Pavia, D.L., Lampman, G.M., Kriz, G.S., and Engel, R.G. Introduction to Organic Laboratory Techniques,
A Microscale Approach; Saunders College Publishing: New York, 1995; 2nd; pp. 168-172.