Nothing predicted the destination of a good-looking Internet search
I just googled “heaviest gas”
Of course, the first result (Radon) was wrong by a wide margin
The second one (WF6) was much closer to the truth, but I decided to take 10 minutes to see if Mother Nature knew something more serious
Remember that updating dynamic programming or clustering methods is much better for my career than chasing obscure gases
This quest wasaddictive
Adds unexpectedly
Of course, the longer my research, the more alien and unfamiliar compounds I encountered, some known only to a few people on earth
Some were so little known that I began to see typos or errors in many of the This and That Compound Dictionaries I looked at
Still, each new chemical offered new ideas and challenged, “Hey, can you find something that’s a heavier gas than me? “
Like reconstruction, this work could not be finished – only stopped
But then I was disappointed that all these results “disappear after time”
Therefore, here is a list of the heaviest gases found in nature
For the purposes of this article, “gas” is any substance that has a boiling point below +20 C at normal atmospheric pressure and is stable enough to be measured under such conditions
“Heavier” simply means molecular weight
Although it is not entirely clear, I doubt that anyone has produced enough of these chemicals to determine their exact density in gaseous form
With a molecular weight of 224 and a boiling point of 156 C [10] , this gas is probably the heaviest sulfur-containing gas, 15 times that of the well-known SF6 gas and 78 times that of air times heavier
Of course, I wouldn’t recommend trying this with SF5C(O)CF3—unless you’ve had enough of it somewhere, somehow
2 Let’s continue with N(CF3)2CF=CF2 (mw 233, bp 137 C, [20, p 648])
There is an entire industry dealing with these types of compounds
For aviation use, they must have a boiling point below -40 °C and often contain fluorine, chlorine or bromine, so they are very heavy
Admission to this club is limited to chemicals that do not adversely affect human health
3 P(CF3)3 [mv 238, pp 173 C, (30, p 323]), AKA tris(trifluoromethyl)phosphine, is probably the heaviest gaseous phosphorus compound
Their molecular weights are the same 238, but structurally they are different
One is perfluorobutane, which has a boiling point of −17 C [50] and 0 C [60, pp 6–70], and the other is perfluoroisobutane
Theoretically, the speed of sound in this gas is only 119 m/s under normal conditions, which is enough to turn a 5th octave C into a 3rd octave F#, unless he loses consciousness through an anesthetic effect Not sure
6 The next one is best found only in a well-equipped laboratory: Tellurium Hexafluoride TeF6 (mw 2416, bp
It is a “colorless, highly toxic gas with a very unpleasant odor” I always wondered – how do people know this?
7 Pentafluoroiodoethane CF3CF2I (mw 2459, bp 13 C, [80, p 424], [90])
Start with good old ethane C2H6, replace one hydrogen with iodine and the rest with fluorine
Listed as a potential anesthetic [80], it is probably not toxic – unless self-knockout or overdose is considered
8 The same is true for decafluorodiethyl ether C4F10O (mw 254, bp 0 C [80, p 413])
9 The next compound, perfluoropropyltrifluoromethyl ether CF3OCF2CF2CF3 (mw 254, bp 674 C, [20, p 650]) is listed as a potential fire extinguisher, even though it belongs to the same family
F5TeOF (mw 2576, “extrapolated” bp 06 C, [100, p 778])
Probably called “Tellurium hypofluorite”, probably poisonous and smelly
Almost anything volatile with tellurium has at least a little noxious and unpleasant odor
This next gas is TeClF5 Tellurium(VI) chloride fluoride (mw 258, bp 135 C, [100, p 776])
Iodine heptafluoride IF7 (mw 2599, bp 48 C, [110]) is a gas nine times heavier than air
Chemically reactive, dangerous
“Can cause fire on contact with organic matter” Looking at its formula, one might think: why don’t we replace one fluorine with something heavier, say Chlorine, and get even heavier IClF6?
Unfortunately, according to Wikipedia, there are almost no interhalogen compounds containing more than two halogens
WF6, the famous tungsten hexafluoride (mw 29783, bp 171 C, [120])
Wikipedia carefully calls it “one of the heaviest gases” but gives no examples of anything heavier
Suffice it to say for now that WF6 is a well-studied chemical used in the semiconductor industry to deposit thin layers of tungsten on silicon
However, it is not a good idea to buy this gas for home assembly
Corrosive, toxic and chemically active, it looks good in the picture, not in the ampoule
At this moment we enter the realm of the land of doubt
Suspicious country
The first habitat is Ge(CF3)3F, tris(trifluoromethyl)fluorogermane
With a molecular weight of 29865, it is only 028% heavier than WF6
It certainly exists, as several sources suggest — see [130, p 61] or [140]
They both give a boiling point of 191 C, so technically it should be a gas
Well, if you read the paper [140] (I did), you’ll come across the following entry: “Fluoride is also anomalous in that all other newly prepared compounds except (CF3) appear as monomeric liquids or solids )3GeF
As shown in Table 11, the sublimation point of this compound is normal compared to other halides, but the melting point, 30 oC, is very abnormal, about 125 oC above the melting point of (CF3)3GeCI
This indicates extensive association in the solid state, possibly through fluorine bridging between germanium atoms And the boiling point of the product is “extrapolated” to 191 C, the melting point is 27-30 C
I’m not sure how to interpret this
Is it solid, unlike the highly volatile molecular Ge(CF3)3Cl (bp 37 C) and Ge(CF3)3Br (bp 49 C) ([130], [140])?
It would be great if someone could repeat the synthesis to verify the results obtained in 1975
It seems strange to think that the molecule Ge(CF3)3F has only appeared on Earth once, 41 years ago, by someone’s experiment
Confusion is resolved by data sources such as chemsrccom bp An even heavier compound is +16 C for Ge(CF3)3ClHowever, after cross-checking with other sources, I conclude that this is some kind of mistake
Chmsrccom seems to list underestimated boiling points for many compounds (eg 61 C for the dreaded Mo2((CH3)2N)6)
Land of Doubt continues with CF3-Te-Te-CF3
According to [130] and [150, page 22], its boiling point is -53 C, 132 times heavier than WF6!
Similar structural but lighter compounds with much higher boiling points include Te(CF3)2 (mw 2656, bp 23 C, [160]), CF3-Se-Te-CF3 (mw 3445, “Orange oil
By comparison, it would be very strange for the heavier CF3-Te-Te-CF3 to be more volatile than its lighter “close relatives”
There are a lot of great bugs in the literature (search for (CF3)SbI2, for example), but at this point you might be wondering – are there any unsuspecting citizens?
Of course there is
How believable can Doubtland be, of course
According to [170], its estimated boiling point is around -40 C
With a molecular weight of 32297, this certainly makes it a very strong candidate for heaviest gas
No one has yet been able to synthesize these chemicals
As a result, we still don’t know if PoF6 exists
And the question of the “heaviest gas” remains open, the answer is lost in the fractal ambiguity of exotic compounds known only to a few experts
No story would be complete without a tour of the Almost Made It City, filled with many unique and curious compounds that are heavier than radon gas
Methylated organometallics such as W(CH3)6, Pb(CH3)4 (bp 100–110 C) or Sb(CH3)3 are often volatile
Of those with an Mv More than 222, the most volatile is probably dimethyl mercury Hg (CH3) 2
Described in [180] as “one of the most potent neurotoxins known”, this fluid bp A temperature of 93-94 C is definitely something to stay away from as much as possible
Replacing the hydrogen in the CH3 group with fluorine offers perfluoromethylated compounds such as bis(trifluoromethyl)selenium Se(CF3)2 (mw 217, bp )
-2 C, [190, p 427]), N(CF3)3 (yes, another gas at -6 C and mw 221, [80, p 425]) or Te(CF3)2 (mw 265, 6), bp 23 C [200])
Most are volatile and most are heavy – see, for example, the liquid Pb(CF3)4 (mw 483, [40])
Further substitutions give rise to an almost infinite variety, too extensive to study fully – As(CF3)2Cl3 (mw 316, bp 94 C [30, bp 325]) or As(CF3)2H (mw 213, 9, pp 19C [30], p 325]
I spent a lot of time looking at them
Sometimes it was felt that the winner – a gas heavier than WF6 – was just around the corner
In the end, the closest to breaking records was mw with became Ge(CF3)4 3486 and bp 317 C ([130], [140])
Still no gas
Still, I strongly suspect that a better candidate might be lurking among the colorful varieties of trifluoromethyl substitutes, but I had to stop and go about my life
PF3 can play a role similar to CF3 by giving rise to volatile metal complexes
Some miracles: Nitrosyl(phosphorus trifluoride)cobalt Co(PF3)3(NO) (mw 3529, bp 81 C [220, bp 3049]), Pt (PF3)4 (mw 547, bp 90, 5) [1] ]) or the continuous family Mo(PF3)6-n(CO)n
Among them, Ni(PF3)4 (mw 4107, bp 705 C, [230, p 1592]) is the closest to becoming a gas
Nickel forms the lowest boiling metal carbonyl – Ni(CO)4 170, pp 43C [240]
Although other metal carbonyls are also often volatile (such as ReH(CO) 5 or Os(CO) 5 ), they all appear as solids or liquids
U(BH4)3(BH3CH3) is volatile but solid (mw 3112) per [250, pp 554]
Other (even simpler) actinide borohydrides are less volatile
WF5Cl is certainly present but is a “yellow solid” [pp 260, 276], WF4Cl2 is “thermally unstable at room temperature, decomposing into tungsten hexachloride and tungsten hexafluoride” [270] and ReClF5 is a “volatile red liquid”, “Dec at rt and gradually at -30
Mp -2” (I love this language!) I found it in the Dictionary of Inorganic Compounds edited by Jane E
Macintyre, but cannot provide you with a link due to fees
Google no longer returns that page (even when I search for those exact terms), probably because I’ve seen “too many” to not buy that book
Org Chemistry
[20]: SEARCH FOR NEW FIRE-RESISTANT CHEMICALS, J
Douglas Mather, PhD Chemical Development Studies, Inc; Robert E
[30]: Fluorine Chemistry, Volume 2, JH Simmons
1989, 28, pp 981-982, 981
[50]: Wikipedia on Perfluorobutane
[60]: CRC Handbook of Chemistry and Physics, 94th Edition, William M
[70]: Wikipedia on Tellurium hexafluoride
[80]: Modern Inhalation Anesthetics, edited by Maynard B
[100]: Chemistry of the Elements, NN Greenwood, A
[110]: Wikipedia about iodine heptafluoride
[120]: Wikipedia on tungsten hexafluoride
[130]: F Perfluorohalogenoorgano Compounds of main group elements
Elements of groups 1 to 5 (except N) and compounds with S (partially)
Am Chemistry
Am Chemistry
Preparation and Stability of (Trifluoromethyl)germanium and (Trifluoromethyl)tin Compounds
(I received this paper and read it)
[150]: Dictionary of Inorganic Compounds, Appendix 3, Jane E
[170]: Monsanto Chemical Company, Abstracts of Progress Reports Section 3, August 16-31, 1945: Summary of Work to Date on Volatile Neutron Source
[180]: Wikipedia article on dimethylmercury
[190]: Advances in Inorganic Chemistry and Radiochemistry, Volume 3, Academic Press, January 1, 1961 – Science
[200]: Synthesis and Characterization of Volatile Trifluoromethyl Alkyl Tellurides, Douglas C
[200]: Synthesis and Characterization of Volatile Trifluoromethyl Alkyl Tellurides, Douglas C
[220]: Dictionary of Inorganic Compounds, Jane E
Macintyre ($3,35700 at Barnes&Noblecom, holy grail! )
[230]: Inorganic Chemistry, Egon Wiberg, Nils Wiberg
[240]: Wikipedia about nickel tetracarbonyl
[250]: Chemistry of Uranium, JJ Katz, Evgeny Rabinovich
[260]: Halogen Chemistry, edited by Victor Gutmann
[270]: Tungsten chloride fluorides: preparation of cis- and trans-tungsten dichloride tetrafluoride and its decomposition into other tungsten fluorides, Chemical Society A Journal of Inorganic Physical Theory · January 1970, G
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