Docsity
Log inSign up
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search Store documents

The best documents sold by students who completed their studies

Search through all study resources
Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

University Rankings

Discover the best universities in your country according to Docsity users

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Exams and Study
Go to the blog

Experiment 9 on Alkene Bromination, Lab Reports of Chemistry

Missouri University of Science & TechnologyChemistry

Alkene bromination is one in which a dihalide such as Cl2 or Br2 is added to a molecule after breaking the carbon to carbon double bond.

Typology: Lab Reports

2020/2021

Uploaded on 05/11/2021

elmut
elmut 🇺🇸

4.6

(16)

285 documents

1 / 4

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Chem 2219 Exp. #9 Alkene Bromination
(bolonc updated 201130) 1
Objective: In this experiment you will learn how to synthesize vicinal dihalides by brominating a solid
alkene with pyridinium tribromide to produce a chiral vicinal dibromide. The solid product will be
isolated by vacuum filtration. To verify the reaction went to completion, the product will be
characterized using the silver nitrate test and verifying its melting point.
* Prior to instrumental analysis, chemists used chemical tests to characterize compounds. Silver has a high
affinity for halogens (X) and will initiate an SN1 reaction to form strong ionic bonds and the precipitate: AgX.
Reading Assignment:
OCLT: p. 365 (reflux); 366 (vacuum filtration); and 357 (silver nitrate test).
Solomons Organic Chemistry, 12th ed. (Note: pages correspond to 12th ed.)
pp. 359-365 (8.11 Electrophilic Addition of Bromine and Chlorine to Alkenes;
8.12 Stereospecific Reactions; and 8.13 Halohydrin Formation)
Concepts:
Bromination, Halogenation, Reflux, Vacuum Filtration
Chemicals:
cinnamic acid, cis-stilbene, trans-stilbene, glacial acetic acid, bromine, pyridinium tribromide
(a.k.a. pyridinium perbromide), silver nitrate and ethanol
Safety Precautions:
Wear chemical splash-proof goggles and appropriate attire at all times.
Ethanol is a flammable liquid. Cinnamic acid and trans-stilbene are flammable solids.
Glacial acetic acid, bromine and pyridinium perbromide are highly corrosive and toxic.
If you spill an acid or a base on the counter or floor, call for a TA or an instructor
to neutralize the spill.
If you spill an acid or a base on your skin, immediately walk to the nearest sink and wash
thoroughly with cold water. Do not attempt to neutralize a spill on your skin.
Materials:
aluminum block, balance, beakers (50 ml), 5 ml conical vial, copper pot, disposable pipet and
bulb, finger clamp, filter flask, filter paper (3 cm), glass stirring rod, graduated cylinder
(10 ml), Hirsch funnel (3 cm), hotplate with magnetic spinner, ice, jacketed water
condenser, magnetic spin vane, melting point apparatus, melting point capillary tubes,
microspatula, ring stand, test tube and tubing (rubber and vacuum)
!
pf3
pf4

Partial preview of the text

Download Experiment 9 on Alkene Bromination and more Lab Reports Chemistry in PDF only on Docsity!

Objective: In this experiment you will learn how to synthesize vicinal dihalides by brominating a solid alkene with pyridinium tribromide to produce a chiral vicinal dibromide. The solid product will be isolated by vacuum filtration. To verify the reaction went to completion, the product will be characterized using the silver nitrate test and verifying its melting point.

  • Prior to instrumental analysis, chemists used chemical tests to characterize compounds. Silver has a high affinity for halogens (X) and will initiate an SN1 reaction to form strong ionic bonds and the precipitate: AgX. Reading Assignment: OCLT: p. 365 (reflux); 366 (vacuum filtration); and 357 (silver nitrate test). Solomons Organic Chemistry, 12th^ ed. ( Note: pages correspond to 12th^ ed.) pp. 359-365 (8.11 Electrophilic Addition of Bromine and Chlorine to Alkenes; 8.12 Stereospecific Reactions; and 8.13 Halohydrin Formation) Concepts: Bromination, Halogenation, Reflux, Vacuum Filtration Chemicals: cinnamic acid, cis-stilbene, trans-stilbene, glacial acetic acid, bromine, pyridinium tribromide (a.k.a. pyridinium perbromide), silver nitrate and ethanol Safety Precautions: Wear chemical splash-proof goggles and appropriate attire at all times. Ethanol is a flammable liquid. Cinnamic acid and trans-stilbene are flammable solids. Glacial acetic acid, bromine and pyridinium perbromide are highly corrosive and toxic. If you spill an acid or a base on the counter or floor, call for a TA or an instructor to neutralize the spill. If you spill an acid or a base on your skin, immediately walk to the nearest sink and wash thoroughly with cold water. Do not attempt to neutralize a spill on your skin. Materials: aluminum block, balance, beakers (50 ml), 5 ml conical vial, copper pot, disposable pipet and bulb, finger clamp, filter flask, filter paper (3 cm), glass stirring rod, graduated cylinder (10 ml), Hirsch funnel (3 cm), hotplate with magnetic spinner, ice, jacketed water condenser, magnetic spin vane, melting point apparatus, melting point capillary tubes, microspatula, ring stand, test tube and tubing (rubber and vacuum)

Alkene Bromination Procedure

  1. Preheat the hot plate and aluminum block at a heat setting of ~ 160 - 180 oC while you assemble your glassware.
  2. Put together a reflux set-up* as shown to the right. *Note: Verify that there is an o-ring in the black cap before attaching the conical vial to the jacketed water. Do not lower empty glassware into Al block; it will cause the glassware to crack. A thermometer is not necessary to monitor the reflux.
  3. In a 5-ml conical vial, weigh out ~ 100 mg of trans-stilbene or ~150 mg of trans-cinnamic acid. ( Choose one or the other. Do not use both .) Record the exact mass to the nearest mg (0.00 1 g).* Record which alkene was chosen. Record the physical properties of the alkene. *Note: The alkene should be weighed and the mass recorded to the nearest mg. This is important because it is the limiting reagent and will be used to calculate the theoretical yield of the product. Figure 1: Reflux Apparatus Set-up
  4. In a 10 ml graduated cylinder, measure out ~2.0 ml acetic acid ( located in the hood ). Add the acetic acid to the alkene in the 5-ml conical vial.
  5. Weigh out the pyridinium tribromide. [200 mg for trans-stilbene. 385 mg for trans-cinnamic acid.] Record the exact mass to the nearest mg (0.00 1 g).* Record the physical properties of the reactant. *Caution: Glacial acetic acid has a sharp odor and will cause chemical skin burns. The pyridinium tribromide is corrosive and a lachrymator. It will cause skin burns and is corrosive to metal. Be careful when handling these substances.
  6. Add the the pyridinium tribromide to the solution in the 5 ml conical vial.
  7. Add the large magnetic spin vane (to regulate boiling and avoid bumping), attach the jacketed water condenser. Start the stirring. Attach the thin walled water hoses to the condenser. Note: Connect the hoses so that water travels against gravity (cooling water comes into the bottom and drains out the top). That is, the lower hose attaches to the water spigot. ( You may have to remove the plastic splash guard from the spigot to attach the hose .) The upper hose needs to be lowered into the water trough to prevent water from pooling on the lab bench. Turn the water on low. Water should go in the bottom of the condenser jacket slowly. ( If there is a lot of bubbling in the condenser, turn the water down .) Do not let the rubber tubing touch the top of the hotplate. It will melt.

  1. Run the silver nitrate test on the product.* Record observations. In a small test tube, add a small amount of the product – roughly the same amount that you would use for the melting point. Add ~1 ml of ethanol. Swirl or stir the mixture to get it to dissolve. (If the sample does not dissolve, consult an instructor.) Once the sample has dissolved, add an equal volume of 1% AgNO 3 in ethanol solution. The test is positive if the solution becomes cloudy or tiny particulates are observed. *Caution: AgNO 3 will stain your fingers and clothing black. You may want to put a rubber stopper on the test tube before swirling the mixture, so that you do not inadvertently get AgNO 3 on your fingers.

  2. Dispose of chemicals in the halogenated waste container. Clean and return all glassware and equipment. Post Lab:

  3. Determine which compound you produced based on your starting material and the melting point of your product. Record your determination. (See Table 1 Below.)

  4. Determine % Error for the melting point of your product.

  5. Determine theoretical yield and % yield. ( Use your exact initial mass to determine theoretical yield .) Show sample calculations.

  6. Tabulate your results in your lab book.

  7. In your conclusion, discuss the success of the reaction based on the results of the melting point and the AgNO 3 chemical test. If there were any problems, make suggestions for how they could be avoided if you were to redo the experiment. . Table 1: Molar Masses and Melting Points of Reactants and Products Substance Molar Mass (g/mole) MP (oC) trans-cinnamic acid 148.16 133 trans-stilbene 180.25 124 2,3-dibromo- 3 - phenylpropanoic acid 307. (±)- threo 94 (±)- erythro 203 (±)-1,2-dibromo-1,2-diphenylethane 340.07 110 meso - 1,2-dibromo-1,2-diphenylethane 340.07 238 ________________________________________________________________________________________________________________________________________________________________________________________