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From Strawberry Fields to the Chemistry Classroom

By Simone N. Walker, Quyen T. Doan, William J. Heuett, Deana Jaber

From Strawberry Fields to the Chemistry Classroom


 

Abstract

This case study investigates the use of methyl bromide as a pesticide and methyl iodide as an alternative pesticide in strawberry fields in California. By 2005, methyl bromide should have been completely phased out under the Clean Air Act and the Montreal Protocol on Substances that Deplete the Ozone Layer, but the United States requested exemptions and the deadline was renewed to 2015. In 2010, methyl iodide was introduced as a substitute. However, because of the similarities of the chemical reactions of the two pesticides, similar problems surfaced. The case uses a dialogue between “Kelly,” a junior in college studying organic chemistry, and “Jessica,” an environmental scientist at the National Institutes of Health, to introduce students to substitution reactions (SN1 and SN2) of alkyl halides and the factors that affect these reactions. Prerequisite knowledge for the case includes an introduction to organic chemistry, structure and bonding of organic compounds (alkenes and alkynes), and stereochemistry. The case is designed for use in introductory organic chemistry and biochemistry courses but could also be used in biology courses.

   

Date Posted

05/07/2021

Overview

Objectives

  • Recognize the different types of alkyl halides (primary, secondary, or tertiary).
  • Differentiate between SN1 and SN2 reactions of alkyl halides.
  • Predict the final product of the reaction including its stereochemistry.
  • Draw the mechanisms of SN1 and SN2 reactions.
  • Apply the concept of carbocation rearrangement in respective mechanisms, SN1 reactions.
  • Determine the relative stability of carbocation intermediates.
  • Identify and recognize the factors that influence SN1 and SN2 reactions such as the strength of the nucleophile (good or poor) and the solvent used in the reaction (protic or aprotic solvents).

Keywords

Organic chemistry; alkyl halides; substitution reactions; nucleophilic substitution; nucleophile; pesticides; methyl bromide; methyl iodide; SN1; SN2; strawberries; farming

  

Subject Headings

Biochemistry
Environmental Science
Organic Chemistry

EDUCATIONAL LEVEL

Undergraduate lower division, Undergraduate upper division

  

FORMAT

PDF

   

TOPICAL AREAS

Policy issues, Regulatory issues

   

LANGUAGE

English

   

TYPE/METHODS

Analysis (Issues), Dilemma/Decision, Directed

 

 

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