dehydobromination[1][1][1] - Peak Peak 1 Holly Corbitt Peak...

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Peak 1 Peak 2 Peak 3 Holly Corbitt 1/25/10 Partner: Shu M. Chem 242 Dehydrobromination Purpose: To perform a bimolecular elimination (E2) reaction and use gas chromatography to determine the product distribution. Compare results with the theoretical product. References: Pavia et. Al. Organic Lab Techniques, 4 th edition. P. 210 – 250. Instructor handouts MSDS.com Safety info: -OtBu is a very strong base. Do not touch or swallow. 2-bromobutane: don’t inhale and don’t use in car. Reactions : Equation 1: 1-bromobutane + -Ot-Bu Br | CH 3 CH 2 CH 2 CH 3 +(CH 3 ) 3 CO- CH 2 = CHCH 2 CH 3 (major – 100%) Equation 2: 2-bromobutane + -OtBu CH 3 CH 2 CH 2 CH 3 + (CH 3 ) 3 CO- CH 2 = CHCH 2 CH 3 (major product - 55%) | Br AND CH 3 CH 2 CH 2 CH 3 + (CH 3 ) 3 CO- + | Br (2 nd major – 29%) (minor – 16%) 1
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Equation 3: 2-bromobutane + -OH/ EtOH CH 3 CH 2 CH 2 CH 3 + -OH - ---- CH 2 = CHCH 2 CH 3 (minor product – 24%) | EtOH Br AND CH 3 CH 2 CH 2 CH 3 + -OH ------ ---- + | EtOH Br (major – 58%) (minor – 18%) Procedure: Set up apparatus for collecting products. Set up heat/stir plate next to a jack. On the jack place a 400ml beaker filled almost to the top with water. On the heat/stir plate place a 50ml wide mouth beaker filled with water and begin to heat. Using a ring stand secure a 5ml conical vial (reaction vial) and submerge bottom half in heated water. In the 400ml beaker secure an inverted test tube filled with water, (Premark 2mL ), and slip s-shaped tube under the inverted test tube. Add 3.0 mL of base, -OtBu, to a 5-mL conical vial. Add a triangular stir bar and 0.32 mL of 2- bromobutane to the vial. Grease the ground-glass joint and connect the S-shaped gas collection tube to the vial. Stir the solution and heat the reaction slowly (to a maximum of 90 °C). After collecting 2 mL of gas in an inverted test tube (gas that is mostly air), replace the test tube with open ended vial (filled with water) with a rubber septum. Continue collecting gas until you have collected approximately 4 mL. Extract gas using a needle syringe and analyze the sample using a gas chromatograph. Physical Properties of Products: Compound MM g/mol Boiling Point 1-butene 56.11g/mol -6.3 C ̊ Trans -2-butene 56.11 g/mol 1 C ̊ 2
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Cis- 2-butene 56.11 g/mol 4 C ̊ Data/ Results: Group 1-bromobutane + -OtBu 2-bromobutane + -OtBu 2-bromobutane + -OH/EtOH 1- butene Trans- 2- butene Cis-2- butene 1- butene Trans- 2- butene
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This note was uploaded on 02/17/2010 for the course CH CH242 taught by Professor Dr.cohen during the Spring '10 term at MGH Institute of Health Professions.

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dehydobromination[1][1][1] - Peak Peak 1 Holly Corbitt Peak...

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