BromicAcid - 30-1-2004 at 20:37
This was just something that crossed my mind. Acids such as HClS and HClS2 and HClS3 and HClS4, etc. with all the other halogens. Do they exist? I
don't think they would fair well in water. I was thinking that you would have to add the sulfur halogen compound to liquefied hydrogen sulfide
and then it would react like an acid anhydride.
I'm assuming that they would be much weaker then their oxoacid counterparts due to the weaker electronegativity of sulfur but there would be so
many more possible compounds considering the variable oxidation numbers of sulfur (well there would be less because it wouldn't be able to
oxidize the halogen like oxygen would but oh well). I picture these compounds as being easily polymerized but at such low temperatures I think they
would be stable. Anyone have any experience or thoughts?
I haven't looked into it but the thought seemed somewhat unique so I figured it could go up here.
Sorry
chloric1 - 31-1-2004 at 10:04
Yeh I do not think they exist. For one hydrogen sulfide is oxidized by all halogens. Sulfur is a MUCH stronger reducer than oxygen and halogen-oxygen
compounds are unstabel as is. Even if you could make a thiochlorate for a nanosecond it would still break apart into chloride, dithionate, etc. But
if you are so inclined I would start with anhydrous DMSO for your reactions. DMSO is less acidic than water and it is fairly dielectric. Plus it is
sulfur based but beware I seen in the literature that DMSO can oxidize organics. Also acetonitrile may be of considerable interest.
Pyrovus - 29-3-2004 at 00:19
The trouble with acids like HClS4 is that, due to the fact that chlorine is more electronegative than sulphur, this would put chlorine in the -7
oxidation state (as opposed to HClO4 in which chlorine is in the +7 oxidation state). Hypervalent compounds form only when the atom is in a positive
oxidation state. This is because atoms don't show any tendency to gain control over more electrons than are needed to complete the noble gas
configuration. For instance, fluorine forms F-, but not F--. For this reason hypervalent compounds do not form in which the atom has a negative
oxidation state. Compounds in which the atom has a positive oxidation state (eg HClO4) form by virtue of the fact that the attached atoms (in this
case oxygen) have a strong tendency to form the noble gas configuration and are electronegative enough to be able to steal partial control of
electrons from chlorine in order to achieve this. While in this case the chlorine has 14 electrons in it's outer shell, the net effect is that
the chlorine has lost control over electrons, because they spend much more time around the oxygens. However, sulphur analogues of oxyacids should
theoretically be possible for halogens with electronegativity less than sulphur - trouble is that the only (discovered) halogen fitting that category
is astatine! With a half life of 8.3 hours for the most stable isotope, this unfortunately would make the investigation of the acids HSAt, HAtS2 etc
rather difficult and dangerous, not to mention expensive. Still, maybe one day they'll discover a superheavy halogen in the island of stability
with a decent half life . . .
[Edited on 29-3-2004 by Pyrovus]