Atmospheric Chemistry of Titan |
Atmospheric Chemistry of Titan |
May 2 2010, 03:38 AM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Here is a "Benzene-O-Vision" graphic showing the amount of benzene and phenyl radicals at high altitudes on Titan. This is based on detections of benzene and phenyl radical (which recombined in the sample chamber to make benzene) using the INMS instrument during closest approach. The numbers are normalized to constant pressure altitude, roughly 1000 km.
The data was taken from Table 1 in: Vuitton et al, Journal of Geophysical Research 113 (2008) E05007. "Formation and distribution of benzene on Titan". doi: 10.1029/2007JE002997 [EDIT 5/24/10: Article freely available here] and overlaid on a map of Titan. The authors mentioned that the errors in these measurements are 20%. These detections are well above the detached haze layer. Most are at the same sun azimuth angle. (T23 observation had the lowest angle.) Assuming that the temporal difference is minimal (each dot is from a different flyby), there doesn't appear to be an obvious correlation with latitude. This graphic does show that benzene is present even waaaay up in the thermosphere and ionosphere. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jul 23 2010, 12:17 PM
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
Cyanogen (C2N2) [NC-CN]
According to the Krasnopolsky 2009 model, cyanogen forms by two main routes. The first route (53% of cyanogen formation) is from the attack of nitrile (.CN) radical on acetonitrile radical (.CH2CN) which then kicks out methylene carbene and forms a new bond between the two nitrile carbons. [I’m baffled by this mechanism, why break a perfectly good C-C bond? You’d think the two radicals would combine to form malononitrile (propanedintrile (NCCH2CN) – a nice stable molecule and handy organic building block] The other main route (47% of cyanogen formed on Titan) uses cyanomethylene carbene :CH(CN) and an excited naked nitrogen atom. (The top reaction in the scheme shows the formation of the cyanomethylene carbene from the reaction of excited naked nitrogen and acetylene). In this case, the :CH(CN) carbene reacts with another atom of excited naked nitrogen to form a radical carbene. This is shown as the fully stepwise mechanism, it is possible that some of these steps could be concerted. The next step is the radical carbon electron combining with one of the nitrogen nitrene electrons to form a C-N double bond, leaving an unpaired electron on the nitrogen – a nitrogen radical. The last step is a C-H bond hemolytic cleavage followed by the unpaired electrons, one from the nitrogen radical and one from the new carbon radical, jumping in together to form a C-N triple bond. -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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