KinPrtIfall04 - Alkyl Halide, Hydrolysis Reaction Part I...

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Alkyl Halide, Hydrolysis Reaction Part I (prepared by Jyotsna Pradhan Ph.D. updated Oct 1998) Note: This is a modified procedure. You need to read your textbook for the background and the final calculations. (See experiment 22.) This experiment consists of measuring the concentration of a substrate that has reacted in a hydrolysis reaction, with respect to time elapsed from the start of the reaction. The hydrolysis reaction of either tertiary butyl bromide or α -phenylethyl bromide in at least two solvents of differing polarities will be studied. The solvent systems to be used are given below. t-Butyl bromide in: A) 35% acetone solution in water B) 20% acetone solution in water α -Phenylethyl bromide in: A) 60% ethanol solution in water B) 45% ethanol solution in water The data obtained will be handled graphically to obtain a rate constant and calculate the half-life of the reaction for each solvent system. Comparison of the values in the two solvents should give insight into the effect of solvent polarity on the mechanism and the rate of the reaction of the hydrolysis reaction. Because the alkyl halides hydrolyze rapidly under conditions used in this experiment, students must perform the kinetic studies working in pairs. One student will measure the time while the other one does the addition of base and records the data. These roles may be reversed for the study of the second solvent system so that each student has a feel for different aspects of the experiment. Each student pair will be assigned one of the alkyl halides listed above to study. Data for the other halide’s kinetic study may be obtained from another group. Material Prep (I will assign two students to prepare these) Prepare a stock solution of ONE of the alkyl bromides, which will be assigned to you by your instructor, according to the following instructions: t-Butyl bromide : dissolve about 0.3 g t-Butyl bromide in 50 mL of dry, reagent-grade acetone. α -Phenylethyl bromide : dissolve about 0.6 g α -Phenylethyl bromide in 50 mL of dry, reagent- grade acetone. Store these solutions in a stoppered 125 mL Erlenmeyer flask to protect them from moisture. Prepare four 125 mL Erlenmeyer flasks as needed to carry out the experiment. Label the flasks as A run , A inf , B run , and B inf . Each flask should contain 50 mL of the appropriate solvent (A or B), and 2-3 drops of bromothymol blue indicator. Flasks “A inf ” and A run ” will contain solvent ‘A’ and “B inf ” and “B run ” will contain solvent ‘B’. The indicator, Bromothymol blue, has a yellow color in acid solution and a blue color in alkaline solution. Fill a 50 mL burette with approximately 0.01 N sodium hydroxide solution that will be provided.
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This note was uploaded on 07/10/2011 for the course BCH 4033 taught by Professor Stern during the Summer '11 term at UNF.

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KinPrtIfall04 - Alkyl Halide, Hydrolysis Reaction Part I...

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