Lesson plan
Zeisel determination
The Zeisel determination or Zeisel test is a chemical test for the presence of esters or ethers in a chemical substance. It is named after the Czech chemist Simon Zeisel (1854–1933). In a qualitative test a sample is first reacted with a mixture of acetic acid and hydrogen iodide in a test tube. The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol or a carboxylic acid. By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with silver nitrate. Any alkyl iodide present will give a reaction with the silver compound to silver iodide which has a red or yellow color. By filtering and weighing this precipitate it is possible to quantitatively calculate the number of iodine atoms and hence alkoxy groups. For example, prior to the development of the more precise methods of NMR spectroscopy and mass spectrometry, the Zeisel test was widely used to determine the number of methoxy (-OCH 3 ) and ethoxy (-OCH 2 CH 3 ) groups in carbohydrate and organophosphorus insecticides. An alternative qualitative Zeisel test can be done with the use of mercury(II) nitrate instead of silver nitrate, leading to the formation of scarlet red mercury(II) iodide. Synthetic applications:
Article summary
The Zeisel determination or Zeisel test is a chemical test for the presence of esters or ethers in a chemical substance. It is named after the Czech chemist Simon Zeisel (1854–1933). In a qualitative test a sample is first reacted with a mixture of acetic acid and hydrogen iodide in a test tube. The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol or a carboxylic acid. By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with silver nitrate. Any alkyl iodide present will give a reaction with the silver compound to silver iodide which has a red or yellow color. By filtering and weighing this precipitate it is possible to quantitatively calculate the number of iodine atoms and hence alkoxy groups. For example, prior to the development of the more precise methods of NMR spectroscopy and mass spectrometry, the Zeisel test was widely used to determine the number of methoxy (-OCH 3 ) and ethoxy (-OCH 2 CH 3 ) groups in carbohydrate and organophosphorus insecticides. An alternative qualitative Zeisel test can be done with the use of mercury(II) nitrate instead of silver nitrate, leading to the formation of scarlet red mercury(II) iodide. Synthetic applications:
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.