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for the following experiment what is the structural equation and a balanced stoichiometric equation

for the following experiment what is the structural equation and a balanced stoichiometric equation

Organic Chemistry: A Guided Inquiry
Organic Chemistry: A Guided Inquiry
2nd Edition
ISBN:9780618974122
Author:Andrei Straumanis
Publisher:Andrei Straumanis
Chapter5: Resonance
Section: Chapter Questions
Problem 8E
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for the following experiment what is the structural equation and a balanced stoichiometric equation

EXPERIMENT 11 RADICAL BROMINATION OF A HYDROCARBON PURPOSE: To prepare an alkyl halide by direct light-initiated radical substitution. To demonstrate basic reaction methods and stoichiometric calculations. READ ABOUT: mechanism of radical halogenation, micro ground glass jointware EQUIPMENT: 10 mL round bottom flask, micro condenser, micro drying tube, Hirsch funnel, vacuum flask, light source. CHEMICALS: bibenzyl, dichloromethane, bromine solution (10% v/v in dichloromethane), toluene, cyclohexene HAZARDS: Bromine is toxic and corrosive. Avoid breathing its vapors or allowing it in contact with skin or eyes. Immediately wash any spill with sodium bicarbonate. Hydrogen bromide gas produced by this reaction is an irritating corrosive gas. Carry out the reaction using an acid gas trap. The product, 1,2-dibromo-1,2- diphenylethane, and other side products may be lachrymatory. In addition to the usual items, pre-lab work should include a structural and balanced equation and the following: PRE-LAB: a) Calculate the approximate mass of bibenzyl needed according to the procedure below. b) Calculate the number of moles of bromine to be used. c) Using (b) and the equation above, determine the limiting reagent. d) Using (c) and the equation, calculate the theoretical yield of product PROCEDURE: 1) Assemble the apparatus as shown in Figure 8. In the drying tube, place a small, loose plug of glass wool near the bend, fill the tube loosely with KOH flakes, and close with another loose glass wool plug. Support the entire apparatus on a ring stand with a clamp on the condenser. 2) Disconnect the flask and measure 1.4 millimoles of bibenzyl directly into it. Add 2 mL of dichloromethane and swirl the flask to dissolve all the bibenzyl. Reconnect the flask to the condenser. Drying tabe KOH Glass wool FIGURE 8 Condenser 10 ml. Round- bottom flask 3) Move the entire setup into a hood and remove the drying tube. Using the pipet provided, carefully measure about 2.0 mL of 10% bromine-dichloromethane solution and add it through the top of the condenser. 4) Replace the drying tube on the apparatus. Swirl the mixture gently to mix. Carry the entire apparatus to the source of light. This is preferably direct sunlight, but may be an intense lamp. 5) Upon exposure to light a reaction should occur. Hydrogen bromide gas bubbles are expelled from the reaction solution, the bromine color may start to fade, and a white, finely crystalline solid precipitates in the reaction flask. 6) Swirl the flask every few minutes to mix the reaction suspension and expose fresh solution to the light. Expose the reaction to light for 15 to 20 minutes, or until all the bromine color has discharged.
Transcribed Image Text:EXPERIMENT 11 RADICAL BROMINATION OF A HYDROCARBON PURPOSE: To prepare an alkyl halide by direct light-initiated radical substitution. To demonstrate basic reaction methods and stoichiometric calculations. READ ABOUT: mechanism of radical halogenation, micro ground glass jointware EQUIPMENT: 10 mL round bottom flask, micro condenser, micro drying tube, Hirsch funnel, vacuum flask, light source. CHEMICALS: bibenzyl, dichloromethane, bromine solution (10% v/v in dichloromethane), toluene, cyclohexene HAZARDS: Bromine is toxic and corrosive. Avoid breathing its vapors or allowing it in contact with skin or eyes. Immediately wash any spill with sodium bicarbonate. Hydrogen bromide gas produced by this reaction is an irritating corrosive gas. Carry out the reaction using an acid gas trap. The product, 1,2-dibromo-1,2- diphenylethane, and other side products may be lachrymatory. In addition to the usual items, pre-lab work should include a structural and balanced equation and the following: PRE-LAB: a) Calculate the approximate mass of bibenzyl needed according to the procedure below. b) Calculate the number of moles of bromine to be used. c) Using (b) and the equation above, determine the limiting reagent. d) Using (c) and the equation, calculate the theoretical yield of product PROCEDURE: 1) Assemble the apparatus as shown in Figure 8. In the drying tube, place a small, loose plug of glass wool near the bend, fill the tube loosely with KOH flakes, and close with another loose glass wool plug. Support the entire apparatus on a ring stand with a clamp on the condenser. 2) Disconnect the flask and measure 1.4 millimoles of bibenzyl directly into it. Add 2 mL of dichloromethane and swirl the flask to dissolve all the bibenzyl. Reconnect the flask to the condenser. Drying tabe KOH Glass wool FIGURE 8 Condenser 10 ml. Round- bottom flask 3) Move the entire setup into a hood and remove the drying tube. Using the pipet provided, carefully measure about 2.0 mL of 10% bromine-dichloromethane solution and add it through the top of the condenser. 4) Replace the drying tube on the apparatus. Swirl the mixture gently to mix. Carry the entire apparatus to the source of light. This is preferably direct sunlight, but may be an intense lamp. 5) Upon exposure to light a reaction should occur. Hydrogen bromide gas bubbles are expelled from the reaction solution, the bromine color may start to fade, and a white, finely crystalline solid precipitates in the reaction flask. 6) Swirl the flask every few minutes to mix the reaction suspension and expose fresh solution to the light. Expose the reaction to light for 15 to 20 minutes, or until all the bromine color has discharged.
7) Move the setup into a hood and remove the drying tube. Allow the mixture to "breath" for a few minutes so that the bulk of the remaining HBr can escape. Do not remove the mixture from the hood until no HBr fumes are observed. 8) Add cyclohexene dropwise through the condenser, with until the unreacted bromine is AUT consumed. Any reddish material should disappear and the suspension should have a white to yellow color. e 9) Cool the flask for a few minutes in an ice bath. 10) Vacuum filter the suspension with a Hirsch funnel and vacuum flask. Wash the crystalline mass with 2 mL of ice-cold distilled water and air-dry the material for several minutes on the funnel. 11) Recrystallize the crude product from toluene. Add the air-dried crystals, a boiling stick, and about 10 mL of toluene to small beaker. Bring this suspension just to boiling on a steam bath and add small portions of toluene to the boiling solution until the white solid just dissolves. Remove the flask from the heat source, remove the boiling stick and allow the solution to cool slowly to room temperature. Crystals of the product should reform. 12) Collect the product by vacuum filtration and air dry. 13) Determine the mass and melting range of the final product. 14) Calculate the percent yield of product obtained. Compare the melting range of the product to that listed in the literature. 15) Turn in your product for evaluation. 52
Transcribed Image Text:7) Move the setup into a hood and remove the drying tube. Allow the mixture to "breath" for a few minutes so that the bulk of the remaining HBr can escape. Do not remove the mixture from the hood until no HBr fumes are observed. 8) Add cyclohexene dropwise through the condenser, with until the unreacted bromine is AUT consumed. Any reddish material should disappear and the suspension should have a white to yellow color. e 9) Cool the flask for a few minutes in an ice bath. 10) Vacuum filter the suspension with a Hirsch funnel and vacuum flask. Wash the crystalline mass with 2 mL of ice-cold distilled water and air-dry the material for several minutes on the funnel. 11) Recrystallize the crude product from toluene. Add the air-dried crystals, a boiling stick, and about 10 mL of toluene to small beaker. Bring this suspension just to boiling on a steam bath and add small portions of toluene to the boiling solution until the white solid just dissolves. Remove the flask from the heat source, remove the boiling stick and allow the solution to cool slowly to room temperature. Crystals of the product should reform. 12) Collect the product by vacuum filtration and air dry. 13) Determine the mass and melting range of the final product. 14) Calculate the percent yield of product obtained. Compare the melting range of the product to that listed in the literature. 15) Turn in your product for evaluation. 52
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