New long-lived greenhouse gas discovered by University of Toronto chemistry team

[peoli]

Chemical appears to have highest global-warming impact of any compound to date

TORONTO, ON - Scientists from U of T’s Department of Chemistry have discovered a novel chemical lurking in the atmosphere that appears to be a long-lived greenhouse gas (LLGHG). The chemical – perfluorotributylamine (PFTBA) – is the most radiatively efficient chemical found to date, breaking all other chemical records for its potential to impact climate.

Radiative efficiency describes how effectively a molecule can affect climate. This value is then multiplied by its atmospheric concentration to determine the total climate impact.

PFTBA has been in use since the mid-20th century for various applications in electrical equipment and is currently used in thermally and chemically stable liquids marketed for use in electronic testing and as heat transfer agents. It does not occur naturally, that is, it is produced by humans. There are no known processes that would destroy or remove PFTBA in the lower atmosphere so it has a very long lifetime, possibly hundreds of years, and is destroyed in the upper atmosphere.

“Global warming potential is a metric used to compare the cumulative effects of different greenhouse gases on climate over a specified time period,” said Cora Young who was part of the U of T team, along with Angela Hong and their supervisor, Scott Mabury. Time is incorporated in the global warming potential metric as different compounds stay in the atmosphere for different lengths of time, which determines how long-lasting the climate impacts are.

http://media.utoronto.ca/media-releases/arts/new-long-lived-greenhouse-gas-discovered-by-university-of-toronto-chemistry-team/

[eppur_se_muova]

1. This "gas" has a boiling point of ~180 degrees --

Celsius.

[peoli]

2. Is that why it is only destroyed when it reaches the upper atmosphere?

"There are no known processes that would destroy or remove PFTBA in the lower atmosphere so it has a very long lifetime, possibly hundreds of years, and is destroyed in the upper atmosphere."

[eppur_se_muova]

3. No. It has very strong bonds, especially C-F bonds ...

in the upper atmosphere, very short UV can blast apart even fairly strong bonds. Probably the C-N bond is the weakest, and the first to break.

Those very strong C-F bonds are why Teflon, Viton, and related fluoropolymers are so resistant to chemical attack. Also, the fluorine atoms pretty well surround all the other atoms in the molecule, so there's no other site for reaction. That's why molecules like SF6 and SO2F2 are so resistant to reaction, while analogues such as SeF6 and SO2Cl2 are highly reactive.

You can think of PFTBA as basically three strings of Teflon hanging off of a central nitrogen atom. Any reactions most likely take place at the nitrogen (such as reaction with O or O3), or at one of the carbons immediately adjacent to the nitrogen (such as H2O, presumably verrrrrrry slow).