Lab 2. Flash Distillation - Notes for Students

Are my answers correct?

4. Often we will ask that you scale your procedure up or down, meaning we will change the amounts of material we will use. The following is a procedure as written in an organic lab experiment. Write the procedure out as if you were asked to scale up by a factor of 2. Make any necessary changes to equipment sizes, reaction times, etc. Remember that you should never heat a reaction vessel that is more than ½ full. "In a 50 mL round-bottom flask place 2 grams of compound X and 15 mL of benzene. Reflux the reaction for 30 minutes. After the reaction has cooled, add 10 mL of ice-cold water. Collect the product by vacuum filtration and wash it with two 10 mL portions of ice-cold water."

5. EXTRACTION To 1 ml. of bromine water in a test tube add .5ml chloroform or carbon tetrachloride. Note the color of the liquid layers. Which layer is more colored? What do you call such liquids which do not form a homogenous mixture? Can you possibly make them homogenous? How? Transfer the mixture into a separatory funnel and add 2 ml. more of bromine water and add 1 ml. more of chloroform of carbon tetrachlorides then shake to effect proper mixing. Let out the lower layer through the stem of the funnel. Again add another 2 ml. to chloroform or carbon tetrachloride to the aqueous solution in the funnel and shake as before. How does the color of the chloroform or carbon tetrachloride layer compare with the first extract? How do you explain the difference? Is it possible that after several extractions the chloroform layer will become colorless? Why?

You wash a separatory funnel with soap and water to ensure it is clean before extracting an aqueous solution with dicholormethane. You should take the time to make sure there are no drops of water left inside the separatory funnel. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a True False

Post-lab Questions 1. What would it mean if the melting point had a wide range in temperature rather than a narrow range of one to two degrees? Normal BIIIU X2| X² I → fx | Ix 2. Is your percent recovery of crystals within reason of what you would expect? Explain your anwer. Normal BIIIU X2| X² | → fx | |图|二 3. If you had chosen petroleum ether instead of your solvent what would happen? BII|U X2| X² | → fx | Ix Normal 4. Would there have been a change in your results if activated carbon was not added to the solution before recrystallization? BIIIU X2| X² | → Normal fx | |图|||| !! !! II II

22 Experiment 2 Chromatography 32. A student properly sets up a column chromatography experiment. Although the mixture is soluble in the mobile phase, the sample appears "stuck" at the top of the column and will not elute regardless of how much solvent is applied. What could be the cause of this prob- lem and what could the student do to try and achieve a successful separation? NA disolves in #20 Salt No maybe the compound NASI is to much an the solvent being #20 is to little Vodafo 3. A student performs a separation by TLC on a silica get plate that results in three spots. A red spot is measured 23 mm away from the original sample spot, a blue spot is 42 mm away, and a yellow spot is 49 mm away. The distance from the original spot to where the solvent stopped is 55 mm. a) Calculate the Re value for each component in the mixture. (Show your work and report the correct number of significant figures.) highest polarity. Explain your answer. b) The silica gel plate is polar. Rank the three…

Pls answer 3 & 4

The following sentence has the format “Statement 1 BECAUSE Statement 2”. Decide whether statement 1 is true, whether statement 2 is true, and whether the REASONING (the ‘BECAUSE’ relationship) between them is valid. Statement 1 − “Cyclohexane-1,2-diol elutes from a silica gel chromatography column after cyclohexane-1,2-dione” BECAUSE Statement 2 − “Ketones stick better to silica than alcohols because the C=O group has a larger dipole than the C-OH group.”   Question 6 options: A Statement 1 and Statement 2 are both correct, and the reasoning is valid.  B Statement 1 and Statement 2 are both correct, but the reasoning is NOT valid. C Statement 1 is correct, but Statement 2 is NOT correct.   D Statement 1 is NOT correct, but Statement 2 is correct. E Statement 1 and Statement 2 are both NOT correct

Extraction of Caffeine Post-lab   8. Ethanol is miscible with water. (After all, alcoholic beverages don t separate into an “alcohol‟layer” and a “water layer.”) Assuming that caffeine is soluble in ethanol, could you useethanol as a solvent to extract caffeine from coffee (rather than using dichloromethane asthe extraction solvent)? Explain why or why not. 9. A 12 oz can of Coke contains 46 mg of caffeine. One fluid ounce is equivalent to 29.57 mL(1 oz = 29.57 mL). What is the concentration of caffeine in Coke, in units of mg/mL? Showyour work. 10. What is an alkaloid?