As the name neonicotinoids suggests, these are "new" molecules based on the molecular structure of nicotine shown below:
Development of neonicotinoids began in the 1980s by Shell and1990s by Bayer. Neonicotinoids are generally less toxic to birds and mammals than they are to insects, and, some of the breakdown products are also toxic to insects, this is why they can be used as insecticides.
Consider the structural formula of imidacloprid, an example of a neonicotinoid and one of the most widely used insecticides:
The early 2000s saw the introduction of two other neonicotinoid compounds; clothianidin and thiamethoxam.
Clothianidin can be used as a spray, dust or injectable liquid, depending on which plants it is being to protect.
In 2013 the European Union restricted the use of imidacloprid, clothianidin and thiamethoxam on crops that attract bees.
Suggested Further Reading
IUPAC Nomenclature: http://www.ausetute.com.au/namctut1.html
Introduction to Functional Groups: http://www.ausetute.com.au/fungroup.html
Molecular Formula: http://www.ausetute.com.au/molecularformula.html
2-Dimensional Structural Formula: http://www.ausetute.com.au/structural2D.html
Skeletal Structural Formula: http://www.ausetute.com.au/skeletal.html
Introduction to Polarity of Molecules: http://www.ausetute.com.au/molpolar.html
Intermolecular Forces and Solubility: http://www.ausetute.com.au/intermof.html
Aqueous Solutions (water as a solvent): http://www.ausetute.com.au/aqueous.html
Suggested Study Questions:
- Use molecular model kits to build models of the following molecules:
- Draw a 2-dimensional (full display) structural formula for each of the following molecules:
- Write the molecular formula for each of the following molecules:
- Consider the nicotine molecule. Do you expect it to be soluble in water? Explain your answer.
- Consider a molecule of imidacloprid. Do you expect it to be soluble in water? Explain your answer.
- What property of clothianidin enables it to be used as a spray? Explain this property in chemical terms.
- What alteration to the structure of a nicotine molecule could you make so that it would become more soluble in water?
- Carefully compare the structure of clothianidin and thiamethoxam (the molecular models you built could be useful here). In what ways are the molecules:
- Considering only the structure of nicotine and the neonicotinoids in this article, explain why nicotine might be more toxic to humans than the neonicotinoids.
- Compare the quotes from Dave Goulson and Richard Schmuck in the article. In what ways are the two quotes:
- Imagine you have been asked by your government to decide whether or not to ban the use of neonicotinoids in agriculture. What would you advise? Explain why.