kinetics of solvolysis

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Florida International University *

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Chemistry

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Dec 6, 2023

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Florida International University Department of Chemistry and Biochemistry Experiment #: 11 Jose Miguel Gonzalez Rodriguez PID: 6363794 CHM2210L-U24 11/12/22

Purpose: The main objective of this lab is to observe solvolysis on t-butyl chloride, which will enable an understanding of the principles of the experiment. Special attention will be paid to the impact on the rate of nucleophilic substitution by using the standard method and observing the effects of solvent and temperature. Megan Rowe 09/07/2020 Section U12 Chapter 3: Distillation Lab Purpose: The purpose of this experiment is to assess the efficacy of two types of distillation; fractional and simple. Through this comparison, this experiment was completed by separating cyclohexane and toluene using these two types of distillation approaches. The results were graphed according to the distillate collected versus the temperature in order to examine which method produced an enhanced separation of organic liquid Megan Rowe 09/07/2020 Section U12 Chapter 3: Distillation Lab Purpose: The purpose of this experiment is to assess the efficacy of two types of distillation; fractional and simple. Through this comparison, this experiment was completed by separating cyclohexane and toluene using these two types of distillation approaches. The results were graphed according to the distillate collected versus the temperature in order to examine which method produced an enhanced separation of organic liquids. Introduction : The rate of nucleophilic substitution in alkyl halides can be affected by different factors such as the concentration of the reactants, composition of the alkyl halide, the temperature, and the solvent for the reaction. To examine the impact of these factors we can do what is known as unimolecular solvolysis. This reaction involves a solvent acting as a nucleophile. For this experiment, the reverse of a previously seen SN1 reaction will be studied, obtaining an alkyl halide as a product of the reaction(SEE FIG 1). Figure.1

In the first step, a carbocation and a chloride ion are formed by breaking the carbon-halogen bond in initial alkyl halide. After a reaction with H2O, the carbocation results in formation of the alcohol product and an acid H+. SN1 reactions like this one, occur through multiple steps and its rate is determine by rate-determining step which it’s the slowest step in the reaction. Moreover, it is an unimolecular reaction with only one molecule involved in rate-determining step as it is indicated by the following rate law: Rate = k [R – X] Name Formula M.W Density M.P B.P Solubility Acetone C3H6O 58.08 g/mol 0.8 g/mL 55.8 ℃ -95°C Water, benzene, and alcohol Bromophenol blue C 19 H 10 Br 4 O 5 S 670 g/mol 2.2 g/mL 279 ℃ 273 ℃ Water and Acetic acid T-butyl chloride C4H9Cl 92.6 g/mol 0.87 g/mL 50.6 ℃ -26 ℃ Water Sodium hydroxide NaOH 39.997 2.1 g/mL 1388 ℃ 323°C Water and ethanol

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g/mol Water H2O 18.02 g/mol 0.997 g/mL 0 ℃ 100 ℃ N/A Table of Constants: Name Formula M.W Density M.P B.P Solubility Cyclohexane C6H12 84.16 g/mol 779 kg/m³ 177.4°F (80.75°C) 80.74 °C (177.33 °F) Ether,

alcohol, ac Name Formula M.W Density M.P B.P Solubility Cyclohexane C6H12 84.16 g/mol 779 kg/m³ 177.4°F (80.75°C) 80.74 °C (177.33 °F) Ether, alcohol, ac Procedure:

 A table with columns labeled: trial, time(sec), temp (degree Celsius), k(sec^-1), k avg, and solvent comp was prepared.  A dry 50 mL Burnet with a teflon stopcock graduated in 0.1 mL increment was obtained , and filled with a 0.1 M solution of t- butyl chloride in acetone.  A 10 mL Burnet graduated in 0.05 mL increments was obtained and filled with 0.1 M sodium hydroxide solution.  A 50 mL burnet graduated in 0.1 mL increments and filled with deionized water.  Six 25 or 50 mL Erlenmeyer flak were obtained ensuring that they were clean and dry.  Three of the flasks were labeled as flask 1, and three of the flask as flask 2 for the standard technique method step. Standard technique method:  For flask 1, 3 mL of 0.1 M of T-butyl chloride solution were placed in acetone into each of the three flask labeled as flask 1  For flask 2, 0.3 mL of the 0.1 M sodium hydroxide solution was placed into each of the remaining 3 flasks. Additionally, 6.7 mL of water, and 4 drops of bromophenol blue indicator were also put in. Solution was swirled to mix.  Room temperature was recorded and the time noted, and quickly but carefully the contents of flask one were poured into flask 2.  Mixture was swirled and immediately poured t back into flask 1.  The time of the color change from blue to yellow was noted and the time in seconds was recorded from initial mixing two final color change.  This process was repeated with the remaining pairs of flask.  If the value obtained for these three trials vary by more than 7 seconds, it would be wise  to repeat this portion of the experiment and use the average of six trials to obtain accurate  results  Data was recorded in a table

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 All six flask with were rinsed off with acetone. Effect of temperature :  Two water baths were prepared, one warmed cautiously on a hot plate to approximately 10 ℃ above room temperature, and the second, cooled by the addition of ice to approximately 10 ℃ below room temperature.  Standard method was repeated but allowing the two flask to reach equilibrium in the water bath for about 5 minutes before mixing the solutions.  The mixture was also be kept in the bath until the color change was timed.  Each determination was repeated three times the average of the 3 values was used to  determine K at these two additional temperatures.  Data was recorded. Effect of solvent:  2mL 0.2M solutions of t-butyl chloride was placed in acetone into flask #1.  0.2mL of the NaOH solution, 7.8mL of DI water, and bromophenol were placed into flask #2.  Use the tandard technique method to mix.  Three trials were done. References Keller, Leonard, et al. “Chapter 10” Nucleophilic Substitutions Reactions II- The Kinetics of Solvolysis. Organic Chemistry I & II , Hayden McNeil, 2014, pp. 91-96.