1 / 5

CHEMISTRY 2000

CHEMISTRY 2000. Topics of Interest #5: Detecting TNT. Trinitrotoluene, aka TNT. Trinitrotoluene (TNT) is frequently drawn as shown on the left. It is, however, much more polar than it looks at first glance. We can see this by looking at the complete Lewis structure, shown on the right:

scarlett-parker
Download Presentation

CHEMISTRY 2000

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHEMISTRY 2000 Topics of Interest #5: Detecting TNT

  2. Trinitrotoluene, aka TNT • Trinitrotoluene (TNT) is frequently drawn as shown on the left. It is, however, much more polar than it looks at first glance. We can see this by looking at the complete Lewis structure, shown on the right: • The Lewis structure shown is only one of sixteen, each of which shows positive charges on the nitrogen atoms and negative charges on half of the oxygen atoms. Thus, the average picture has every nitrogen with a charge of +1 and every oxygen with a charge of –½. Erica S. Forzani et al J. Am. Chem. Soc. (2009) 131 pp.1390-1391. As reported in Nature (2009) 457 p.514

  3. Detecting TNT • Since TNT is so polar, it should be soluble in very polar solvents such as ionic liquids. A technique recently developed to detect trace amounts of TNT takes advantage of this property. An ionic liquid is used to pre-concentrate the explosive, making it easier to detect at very low levels. • The ionic liquid used was 1-butyl-3-methylimidazolium hexafluorophosphate (aka BMIM-PF6), shown below: Erica S. Forzani et al J. Am. Chem. Soc. (2009) 131 pp.1390-1391. As reported in Nature (2009) 457 p.514

  4. Detecting TNT • Once dissolved in the ionic liquid, an electrochemical reaction is used to reduce the TNT to a product that is red in colour (see right). • Spectrophotometry is then used to measure the amount of red product generated – which, in turn, indicates how much TNT was present to start with:

  5. Wider Applications • Advantages of this technique include: • It is inexpensive. • The equipment is small and portable. • It is highly sensitive. • It is highly selective for TNT and explosives with similar structures (benzene rings with multiple NO2 groups attached). Thus, it will not give false positive signals for common volatile substances like household cleaners or personal hygiene products. These features are important if the technique is to be useful in practice. (in airport security, perhaps?) Erica S. Forzani et al J. Am. Chem. Soc. (2009) 131 pp.1390-1391. As reported in Nature (2009) 457 p.514

More Related