Lesson Overview: 1-2 Sentences Here

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

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)

Learning Objectives: Students will: 1. Calculate reaction rates using concentration and time. 2. Determine reaction order. 3. Determine solvent dependency for rate.

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.

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)?

Teaching Tips:  Ensure that students wear protective clothing including goggles.  Ensure students know how to use micropipette properly.

References: Adapted from J. Manion, Modular Laboratory Program in Chemistry, J. Jeffers, editor, H. A. Neidig, publisher, 2000, module 714.

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.

Williamson Ether Synthesis: Determination of Rate and Reaction Order

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

Goals:  To learn basic organic synthesis techniques  Determine reaction order and rate under various reaction conditions  Compare different reaction substrates

References: Adapted from J. Manion, Modular Laboratory Program in Chemistry, J. Jeffers, editor, H. A. Neidig, publisher, 2000, module 714.

Experimental:

A.) Br vs. Cl

Objective: Determine reactivity difference between halide substituents.

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

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

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.

Questions: 1. What were the respective reaction rates? 2. What might explain this difference?

B.) Reaction order (two groups)

Objective: Determine reaction order with respect to each substrate.

Materials:  2-bromo-2-methylpropane  2-propanol, D.I. water  phenolphthalein solution  magnetic stir-bar and stir-plate  125 mL Erlenmeyer flask  stopwatch

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.

Group 1 ( 2-bromo-2-methylpropane ):

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

Questions: 1. What were the respective reaction rates? 2. What was the reaction order with respect to tBuBr?

C.) Solvent Dependency

Objective: Determine rate dependence on solvent.

Materials:  2-bromo-2-methylpropane

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

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.

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

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?

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.

Idaho State University’s GK-12 Project http://www.isu.edu/%7Esanghann/Index.html 5