CHM 2210L Chapter Notes - Chapter 1: Xue Xu, Fractional Distillation, Distillation

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15 Apr 2015

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To separate a 1:1 solution of cyclohexane and toluene through simple and fractional distillation and identify differences between temperature and volume of distillation solution between the two methods. 7. 0 ml of stock solution composed of cyclohexane and toluene in a 1:1 ratio is added to a 10-ml conical vial. The vial is buried in sand so that the surface of liquid is beneath the sand. The simple distillation apparatus is set up with the distillation head connected to the conical vial along with the condenser linked with a source of cool water and the adapter for distillate collection. Two thermometers are placed appropriately one in the vial of stock solution and another in the sand. The apparatus is checked for water flow in the condenser and the entire setup is checked by the ta. Heating begins at a rate of 3-4 ocelsius per minute and distillation should be no faster than two drops per minute.

Related Questions

1. In this distillation experiment we start the experiment with 10 mL of liquid mixture ofcyclohexane and toluene. However, it is not possible to obtain all 10 mL back under thecurrent procedure particularly for fractional distillation. Explain why that is the case for distillation and in particular for fractional distillation.

2. How could you modify the experiment and collect all 10 mL of the startingmaterials.

3. Plot a theoretical distillation curve of temperature (y-axis) vs. volume in mL (x-axis) fora 15 mL of a mixture containing 60% 1-propanol and 40% 2-propanol. Are these twocompounds easier to separate by distillation than cyclohexane and toluene? Explain youranswer.

4. In this experiment you were asked to collect two fractions and early fraction and a latefraction. Which of the two fractions would be richer in cyclohexane? Would there be adifference between the percent of cyclohexane in the fractions collected from fractionalvs. simple distillation.

5. What method of purification would you use to purify methanol from a solution ofmethanol and NaCl? Be specific and explain your choice of method.

EAS Bromintation Reaction

To a 50 mL round bottom flask charged with a stirbar and fitted with a reflux condenser, combine 1.780 g N-bromosuccinimide and 7.00 mL acetonitrile. Upon dissolution, add 0.162 g iron (III) chloride and stir the solution for 5 minutes at room temperature. (note* you will see the solution turn from yellow to dark red indicating the formation of the bromine complex. Once the color change is noticed, add 1.065 mL toluene and stir the reaction for 30 minutes at room temperature. Monitor the reaction via TLC using a 30% ethyl acetate in hexanes eluent system.

Multiple Choice:

1. The Electrophile in the bromination reaction is..

A. Br- B. Br+ C. toluene D. Br-Br

2. A benzene ring with activating substituents can be considered a/an...

A. inert compound B. Electrophile C. Nucleophile D. Ringophile

3. Can toluene be separated from the mono substituted bromotoluenes by distillation?

A. Yes by fractional distillation as the boiling points are less than 25 degrees apart B. No the boiling points are within 5 degrees of each other C. Yes by simple distillation as the boiling points are greater than 25 degrees apart

4. 12 principles of Green Chemistry: You work for a pharmaceutical company and you are asked to synthesize a fluorinated compound that will be used to produce a new medicine. The procedure calls for the addition of HF, which is a very reactive and dangerous substance. You figured out a way to slowly produce HF in situ rather than having to add it beforehand/ Which priciple is under consideration:

A 3 B.12 C. 6 D. 10

5. According to green chemistry, what class of catalysts are actually toxic

A. synthetic catalysts B. Heavy metal based catalysts C. Biological protein catalysts D. RNA catalysits

6. Rather than using the historical approach of controlling the concentration or releases of a particular chemical substance through engineering controls or waster treatment procedures, green chemistry:

A changes the intrinsic nature of the substances themselves so as to redue or eliminate the hazard posed by the substances

B. completely eliminates all potential hazards

C. only involves reactions of extremely low concentrations

D. ignores the dwstream effects of chemical substances while attempting to find the efficient synthetic methods

Grignard theoretical yield... also, what is the limiting reactant?

Procedure: The Claisen adapter is fitted to the neck of a 100 mL round bottom flask containing 1-2 crystals of solid iodine and 0.5 g of magnesium metal (Mg). In the side arm of the adapter, place a reflux condenser with water hoses connected, but not flowing. Insert the vacuum connecting tube into the top of the condenser. Place the glass stopper into the other joint of the connecting tube and attach a DRY piece of rubber tubing connected to a drying tube. The drying tube should have two cotton plugs and sufficient DRIERITE (anhydrous CaSO4) between them to ensure that any air getting into the system is dried by the Drierite. Place the separatory funnel in the straight arm of the adapter. Open the stopcock so there is a flow path from the funnel to the flask. Insert a second vacuum connecting tube into the top of the separatory funnel. Place the glass stopper into the other joint of the connecting tube and attach a DRY piece of rubber tubing connected to a drying tube. The drying tube should have two cotton plugs and sufficient DRIERITE (anhydrous CaSO4) between them to ensure that any air getting into the system is dried by the Drierite. Once the apparatus is assembled, use a heating mantle on medium heat to heat the flask until sublimed iodine appears on the inside walls of the flask (rosy color). Close the separatory funnel. The apparatus should now be dry enough to allow formation of the Grignard reagent to occur. After the apparatus has cooled, start the water flowing gently through the condenser. To prepare the phenylmagnesium bromide, add 5 mL of anhydrous ether to the flask (through the separatory funnel) followed by 0.5 mL of bromobenzene. Close the stopcock on the separatory funnel. After a minute or so, bubbling should occur as the reaction begins and the reaction mixture should begin to turn slightly brown. If no reaction appears to begin, warm the flask gently with your hand. When the reaction begins, add 1.5 mL of bromobenzene in 15 mL of ether, and add this solution to the separatory funnel. Slowly add the bromobenzene solution from the separatory funnel dropwise at a rate of about two drops per second. This should be a rate sufficient to keep the reaction going without further heat. There should be sufficient heat from the reaction to maintain the ether at reflux. If the reaction appears to be going too fast and the ether vapors are high on the walls of the reflux condenser, use an ice bath to cool the reaction to the point that the ether vapors are no more than one-third of the height of the reflux condenser. When all of the bromobenzene has been added, heat the reaction at reflux for about 25 minutes with a low heat heating mantle. Prepare a solution of 2.25 g of benzophenone in 10 mL of anhydrous ether (in the closed separatory funnel

CHM 2210L Chapter Notes - Chapter 1: Xue Xu, Fractional Distillation, Distillation

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