<p>Lesson Overview: Laboratory experiment: calculation of reaction rates and Subject area(s): Synthetic and order for the Williamson ether synthesis under varied conditions. Analytical Chemistry National Science Education Standards Addressed: Topic: Reaction rates and order 1. ? Audience: AP chemistry</p><p>Materials: Suggested time: 50 minutes . 2-bromo-2-methylpropane, 2-chloro-2-methylpropane 1. 10 min pre-lab discussion . isopropanol 2. 30 min lab work . deionized water 3. 10 min post-lab discussion . phenolphthalein solution . magnetic stir-bar(s) and stir-plate(s) Resources: . 125 mL Erlenmeyer flask(s) Attached hand-out . 1-200 L micropipette . stop-watch(es) Williamson Ether Synthesis: Determination of Rate and Reaction Order Teacher’s Guide by: Ian Kihara (Pocatello High School)</p><p>Learning Objectives: Students will: 1. Calculate reaction rates using concentration and time. 2. Determine reaction order. 3. Determine solvent dependency for rate.</p><p>Background: The Williamson ether synthesis is a very common and well known reaction in the field of organic chemistry. There are two main reaction pathways including a first and a second order mechanism, depending on the alkyl halide substrate. Students will have a chance to probe this reaction to see which pathway the tertiary 2-bromo(chloro)-2-methylpropane undergoes.</p><p>Assessment Strategy: 1. Are students able to correctly calculate reaction rates? 2. Are students able to determine reaction order and explain the solvent dependency (or lack thereof)?</p><p>Teaching Tips:  Ensure that students wear protective clothing including goggles.  Ensure students know how to use micropipette properly.</p><p>References: Adapted from J. Manion, Modular Laboratory Program in Chemistry, J. Jeffers, editor, H. A. Neidig, publisher, 2000, module 714.</p><p>Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 1 This material was developed with support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program (DGE-0338184) and Idaho State University. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.</p><p>Williamson Ether Synthesis: Determination of Rate and Reaction Order</p><p>OH X H C CH3 H C CH H3C CH3 H3C C CH3 3 3 C C H H C O CH3 0.5 M NaOH 3 H O, iPrOH CH3 X= Br, Cl 2</p><p>Goals:  To learn basic organic synthesis techniques  Determine reaction order and rate under various reaction conditions  Compare different reaction substrates</p><p>References: Adapted from J. Manion, Modular Laboratory Program in Chemistry, J. Jeffers, editor, H. A. Neidig, publisher, 2000, module 714.</p><p>Experimental:</p><p>A.) Br vs. Cl</p><p>Objective: Determine reactivity difference between halide substituents.</p><p>Materials:  2-bromo-2-methylpropane, 2-chloro-2-methylpropane  2-propanol, D.I. water  phenolphthalein solution  magnetic stir-bars and stir-plate  125 mL Erlenmeyer flask  stopwatch</p><p>Procedure: To a clean Erlenmeyer flask equipped with a magnetic stir-bar add 50 mL 2-propanol and 50 mL deionized water. To the flask add 5 drops of phenolphthalein solution and 200 L of 0.50 M NaOH. Add to the flask 50L of 2-bromo-2-methylpropane, immediately start </p><p>Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 2 timing and place on the stir-plate. After the reaction time is taken, clean the flask and stir- bar with deionized water and repeat the experiment with 2-chloro-2-methylpropane.</p><p>Questions: 1. What were the respective reaction rates? 2. What might explain this difference?</p><p>B.) Reaction order (two groups)</p><p>Objective: Determine reaction order with respect to each substrate.</p><p>Materials:  2-bromo-2-methylpropane  2-propanol, D.I. water  phenolphthalein solution  magnetic stir-bar and stir-plate  125 mL Erlenmeyer flask  stopwatch</p><p>Procedure: To a clean Erlenmeyer flask equipped with a magnetic stir-bar add 2-propanol and deionized water. To the flask add 5 drops of phenolphthalein solution and 0.50 M NaOH. Add to the flask 2-bromo-2-methylpropane, immediately start timing and place on the stir- plate. After the reaction time is taken, clean the flask and stir-bar with deionized water and continue to the next experiment.</p><p>Group 1 ( 2-bromo-2-methylpropane ):</p><p>Reaction 1 Reaction 2 Reaction 3 tBuBr 60 L 30 L 120 L 0.5 M NaOH 200 L 200 L 200 L 2-propanol 25 mL 25 mL 25 mL D.I. water 75 mL 75 mL 75 mL</p><p>Questions: 1. What were the respective reaction rates? 2. What was the reaction order with respect to tBuBr?</p><p>C.) Solvent Dependency</p><p>Objective: Determine rate dependence on solvent.</p><p>Materials:  2-bromo-2-methylpropane</p><p>Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 3  2-propanol, D.I. water  phenolphthalein solution  magnetic stir-bar and stir-plate  125 mL Erlenmeyer flask  stopwatch</p><p>Procedure: To a clean Erlenmeyer flask equipped with a magnetic stir-bar add 2-propanol and deionized water. To the flask add 5 drops of phenolphthalein solution and 0.50 M NaOH. Add to the flask 2-bromo-2-methylpropane, immediately start timing and place on the stir- plate. After the reaction time is taken, clean the flask and stir-bar with deionized water and continue to the next experiment.</p><p>Reaction 1 Reaction 2 Reaction 3 tBuBr 50 L 50 L 50 L 0.5 M NaOH 200 L 200 L 200 L 2-propanol 30 mL 50 mL 70 mL D.I. water 70 mL 50 mL 30 mL</p><p>Questions: 1. What were the respective reaction rates? 2. Did the reaction appear to be dependant on the solvent mixture? 3. What physical property could have contributed to this? Why?</p><p>Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 4 This material was developed with support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program (DGE-0338184) and Idaho State University. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.</p><p>Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 5</p>