Q U E E N S C O L L E G E THE CITY UNIVERSITY OF NEW YORK FLUSHING, NEW YORK 11367-1597 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• DEPARTMENT OF CHEMISTRY Chemistry 252 AND BIOCHEMISTRY Spring 2016 Lab. Notes ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Laboratory Notebook
Students must maintain a bound (composition style, not loose-leaf or spiral) laboratory notebook, with pages consecutively numbered. To prepare for the laboratory experiments read the laboratory directions ( in the laboratory text and supplemental notes) for the entire experiment . Pay special attention to details and cautions for handling materials!
It is important to prepare your notebook prior to starting any experiment. This helps you better understand the experiment. Some of the preliminary work on your laboratory notebook should also be done before coming to the laboratory. This would include preparing a set of notes to follow regarding procedures to be followed, preparing tables ready to record data etc. You must record data and observations in the laboratory (and NOT on separate pieces of paper for later transfer into your notebook).
Laboratory Safety
You MUST have suitable eye protection at all times in the laboratory, even if you are not doing any experimental work (others are!). Dispose of chemicals as instructed.
Sample Laboratory Notebook Page
A. Title of Experiment (e.g. Borohydride reduction of a ketone)
B. Concise statement of the type of reaction. (e.g. Reduction of a ketone to an alcohol using a complex hydride reducing agent)
C. Main Reactions ethanol (95%) e.g. C6H5COCOC6H5 + NaBH4 ~~~~ ~~~~~> C6H5CHOHCHOHC6H5
D. Side reactions if any
E Work-up and purification. Use a flow diagram
F. Test reaction if any
G. Answer questions at the end of the experimental procedure
H. Prepare Table of Physical Constant for Reagents and Products (sample shown below)
Substance Mol. Grams Moles Dens Mp B p solub. in solub. in solub. in Mass used used g/100 mL g/100 mL g/100 mL water ethanol ether
Benzil 210.23 0.50 0.024 94-95° insol. sol. sol.
NaBH4 37.83 0.10 0.026 1.074 400°dec. 55 4.0 insol.
Ethanol 46 5.0 mL 78.2° meso- 214.25 137° insol. sol. sol. Hydrobenzoin
I. Calculation:
0.50 Theoretical yield : /210.23 x 214.25 = 0.51 g
Actual yield is : 0.32 g Percent yield : 0.32/ 0.51 x 100% = 63%
Observed Mp. 135-137°
J. Comments if any
K. Other Methods of preparation (if appropriate)
Product Label
Experiment # ; Name of Product Physical Constant actually observed Actual yield in g. (% yield); Tare of container
Student's name #56 Hydrobenzoin Mp. 135-137° C 0.32 g (63%) 27.84 g
______THE EXPERIMENTS ______The pages referred to below are those in the NINTH edition of the Fieser and Williamson Lab Manual.
I. Borohydride Reduction of a Ketone: Hydrobenzoin from Benzil
Read Chapter 56 of the laboratory text (starts page 532) prior to coming to the laboratory. Follow the experimental procedure as described on p.503 with the following modifications: 1) Rather than cooling the flask under a running tap, swirl by hand the flask containing the suspension of benzil in 95% ethanol in a beaker of ice-water; 2) Filter the cooled solution, after the reaction is done, by gravity prior to crystallization, after crystallization collect crystals by suction filtration (Hirsch or small Büchner funnel). Clean-up and disposal: as described in the text, all materials are suitable for disposal in the sink drain, flushed with water. The product is dried, weighed with yield, observed melting point, and your name on the container properly labeled is to be turned in to your laboratory instructor for grading.
II. Diphenylacetylene from E-Stilbene
Read Chapter 59 of the laboratory text (starts on page 542) prior to coming to the laboratory. Follow Experiments 2 ) and 3 ) for the preparation of meso-stilbene dibromide from E-stilbene, and preparation of diphenylacetylene from the dibromide as described in the laboratory text. Disposal of all materials should be performed as described in the laboratory text. The product should be dried, weighed and, placed in a stoppered test tube. The tube, with a proper label, should be turned in to your laboratory instructor for grading.
III. Diels-Alder Reaction
Read Chapter 28 of the laboratory text (starts page 489) prior to coming to the laboratory. Follow the experimental procedure as shown in part 1 and 2 (pp. 492-494) with the following modification: Caution! cyclopentadiene and the dimer are flammable
1) You will use a Bunsen burner flame to crack the cyclopentadiene-dimer in the hood. Add to the cracking flask 10 mL of mineral oil (chaser!). Your set up will be similar to that shown in Figure 19.1 of the laboratory manual. However, you will improvise the fractionating column by simply using a reflux condenser with no water passing through it. Although this is not as efficient as a proper fractionating column, it is adequate for the task at hand. Make sure that the set-up is assembled with care and all the connections are tight. Make sure that the monomeric cyclopentadiene is collected in a receiver that is kept ice cold and protected from atmospheric moisture. The vertical condenser, which act as a fractionating column is not cooled., only the inclined condenser should be cooled thoroughly by running through it very cold water. Keep the freshly prepared cyclopentadiene cold and well stoppered until you need to use it in the Diels Alder Reaction.
2) Keep the excess cyclopentadiene and the residue from the cracking well stoppered until properly disposed. The dimer and monomer of cyclopentadiene have a very strong unpleasant penetrating odor! 3) For Part 2 heating, use the steam cone. 4) Collect the solid product by suction filtration; 5) Discard all organic materials (not your product!) in the Organic Waste Container in the hood. Inform you laboratory instructor that a proper entry be made on the bottle label. The product should be dried, weighed and, placed in a bottle. This bottle, with a proper label, should be turned in to your laboratory instructor for grading.
IV. Aromatic Electrophilic Substitution. Preparation of 1,4-di-tert-butyl-2,5- dimethoxybenezene
Read Chapter 29 of the laboratory text (starts page 314) prior to coming to the laboratory. Follow experiment 2, for the preparation of 1,4-di-t- butyl-2,5-dimethoxybenezene, as given in the laboratory text, p. 318-319. Cleanup as directed in the laboratory text. The product is dried, weighed and placed in a small jar. This jar, properly labeled, is to be turned in to your laboratory instructor for grading.
V. Side chain oxidation of para-nitrotoluene
1) Add 3.0 g of p-nitrotoluene and 3.0g of sodium carbonate to 225mL of water in a 500 mL round bottomed flask and reflux using Bunsen burner for 5 min. 2) To the refluxing solution add 9 g of potassium permanganate portion wise (Roughly 1g for every 3 min) and continue reflux for 15 min.
3) The excess KMnO4 is reduced by adding sat. aq. NaHSO3 solution to the reaction mixture (You can detect traces of permanganate in solution by dipping a spatula into the reaction mixture and touching a filter paper – A pink color around the dark spot of manganese dioxide indicates the presence of permanganate ion); insoluble MnO2 was removed by gravity filtration of the hot mixture into a 600 mL beaker. 4) After the filtrate attains room temperature acidify by the addition of 50% (9+M) aqueous sulfuric acid (check by litmus). 5) After the solution reaches room temperature cool in an ice-bath (if required) and collect the crystallized product by suction filtration. 6) Dispose off the aqueous filtrate by first bringing it to neutral pH by the addition of acid or base as required, and flush down the drain.
VI. Fischer Esterification : Preparation of methyl benzoate
Warning : No flames in the entire laboratory while ether is being used
Read Chapter 40 of the laboratory text (starts page 407) prior to coming to the laboratory. Follow the experimental procedure (starts on page 411) with the following modifications: 1) Since we will be using ether for extraction we will use only the steam cones for both refluxing the reaction mixture and the distillation of the ether.
No flames permit until everyone in the laboratory is ready to do the final distillation of the product
Save all aqueous waste wash portions from the extractions and separately also the recovered ether for proper disposal. The collected drying agent (sodium sulfate ) should be placed in the Solid Waste Container. Advise you laboratory instructor for proper entries about the waste disposal. The distilled product should be weighed and turned in to your laboratory instructor for grading.
VII. Nitration of methyl benzoate
Read Chapter 28 of the laboratory text (starts page 309) prior to coming to the laboratory. Use the methyl benzoate you prepared in the previous laboratory class. If not sufficient it will be supplemented by your laboratory instructor to bring the mass to 6.1 g. Disposal of chemicals is to be followed as indicated in the laboratory text for this experiment. Advise your instructor of any material placed in the Organic Waste Container. The product is dried, weighed with yield, observed melting point, and your name on the bottle properly labeled is to be turned in to your laboratory instructor for grading.
VIII. Preparation of Aniline / Nucleophilic Aromatic Substitution
Aniline prep
Read Chapter 46 of the laboratory text (starts page 451) prior to coming to the laboratory. Follow the instructions of Experiment 1 and 2 with the following modifications: 1) Rather than use the apparatus as described in Figure 6.4, perform the steam distillation by using a three–neck flask. One opening should be stoppered. A second opening is for a dropping funnel, used to top up the water level as needed). The third opening is for a distillation head. . You must use a bunsen burner (not a steam cone) to heat the three neck flask so as to boil the water and generate steam for the steam distillation. The steam cone will not get the flask contents hot enough to generate steam inside the flask. Continue this modified steam distillation until the oily material has been co-distilled (test: catch a few drops of distillate in a little water in a 50 mL beaker!). 2) The aniline will be extracted into dichloromethane. After separation from aqueous phases the solution will be distilled to remove the solvent dichloromethane. Keep aqueous (inorganic) and organic waste solutions separate. Dispose of the inorganic materials as described in the laboratory text. Do not place halogen containing organic solvents into the regular Organic Waste Containers. The dichloromethane is to be placed in a separate halogen containing organic waste container in the hood.
Inform your laboratory instructor of all materials placed in the disposal containers, in order that proper labeling of the waste containers can be done. Record properly in your laboratory notebook the yield of crude aniline. Provide on a separate and also neat sheet of paper the yield, other comments and your name for this part of the experiment.
Nucleophilic Aromatic Substitution: Reactions of 2,4-Dinitrobromobenzene (2,4- DNBB)
This experiment is adapted from "Techniques and Experiments for Organic Chemistry" by A. Ault (Allyn and Bacon, 5th Ed, 1987), pp. 426-427, Expts. 65.2 and 65.3. 2,4-Dinitrophenylhydrazine Prepare a solution of 0.5 g ( 0.002 mol) of 2,4-DNBB in 7,5 mL of 95% ethanol. Heat the solution to boiling ( use a steam cone), and add to it a solution of 0.5 mL (0.010 mol) of 64% aqueous hydrazine (100% hydrazine hydrate in 2.5 mL of 95% ethanol. Allow the light orange solution, which will rapidly turn deep red-purple, to cool slowly for about 15-20 minutes. Collect the resulting crystals by suction filtration and wash them with a little cold ethanol. The product sometimes crystallizes as red-purple prisms and orange blades. Recrystallization of either form from boiling ethyl acetate ( ca. 50 mL per gram) affords a product in the form of orange plates. Discard all waste materials in the Organic Waste Container in the hood. Inform your laboratory instructor so that a proper entry may be made on the label of the container. The product is dried, weighed, and placed in small vial (properly labeled) and turned in to the laboratory instructor for grading.
2,4-Dinitrodiphenylamine
Introduce into 50 mL r.b. flask 15 mL ethanol, 1.24 g (0.005 mol) 2,4-DNBB and 1.0 g (0.011 mol) of aniline. Attach a water cooled reflux condenser and boil gently until all solids have dissolved. Allow the clear solution to cool slowly, at least for 1 hour to room temperature. Collect the red needles by suction filtration. The product should be recrystallized from hot ethanol. The recrystallization will require 75 -100 mL. The product may be dissolves slowly in boiling ethanol. Discard all waste materials in the Organic Waste Container in the hood. Inform your laboratory instructor so that a proper entry may be made on the label of the container. The product is dried, weighed, and placed a small vial properly labeled and turned in to to laboratory instructor for grading.
IX. Preparation of acetanilide
Perform the preparation of acetanilide from the isolated crude aniline as described in the laboratory text (p.457 et seq. You must use at least 5.0 g of aniline. Your laboratory instructor can supply you with some additional aniline, in case you have less from your preparation. Dispose of aqueous solution as described in the laboratory text. The product is dried, weighed and turned in to your laboratory instructor for grading (small jar).
X. Aldol Condensation : Preparation of Dibenzalacetone
Read Chapter 37 of your laboratory text (p 383 et seq.) prior to coming to the laboratory. Follow the experimental procedure described on p. 363 with the following modifications: you will need to dilute the supplied 50% sodium hydroxide solution to the appropriate concentration ( do the calculation!). Follow the waste disposal instructions described in the laboratory text. Inform your laboratory instructor of the amounts of all materials placed in the Organic Waste Container, so that a proper entry may be made on the label of the container. The product is to be turned in to your laboratory instructor for grading (small vial or jar).
Organic Qualitative Analysis of Unknowns ______
Read Chapter 70 of your laboratory text (pages 634 et seq.) prior to coming to the laboratory. You will be assigned three unknown pure compounds which you are to identify. 1. Determine the m.p. or the b.p. (as appropriate) for the unknowns; 2) perform a sodium fusion for the determination of some elements (N, S halogens). For the sodium fusion hold the test tube with a test tube holder rather than the wire gauze as illustrated in the laboratory text; 3) solubility and classification should be done carefully to determine the type of compound present; 4) Final characterization is to be accomplished by the preparation of two solid derivatives per unknown. Directions for the tests and preparation of derivatives are given in the laboratory text. Your unknowns are selected from the list of compounds listed in Tables 70. 70.17. Derivatives should be placed in a properly labeled vial or small test tube and handed in to the laboratory instructor with a neatly written report of your analysis ( in addition to the clear write-up in your laboratory notebook, as you observe and collect your information). Some selected detailed instruction for the preparation of derivatives, using the reagents available in the laboratory are given below, along with listing of the melting points of suitable derivatives. You are to prepare derivatives using only those reagents that are available. Some of the derivatives listed in the laboratory text cannot be prepared because the required reagents are not available. Plan your work ahead. Reagents are not available for all of the classification tests and derivative preparations as listed in the laboratory text. Some of the reagents are either particularly hazardous to handle and also risky for the environment. You should use alternative tests and derivatives, using reagents which are supplied to you in the laboratory. A list of reagents that are available is given. In addition there are also the reagents you have used in the course of the semester. Be careful to refer to the lecture text and the laboratory text to ascertain which reagents are to be used for a particular determination. Your laboratory instructor will not tell you immediately if you are correct, or not until you actually hand in your report and the derivatives. If you are incorrect, you will be given some instructions how to proceed.