another link Isotope effect produces new type of chemical bond
http://www.rsc.org/chemistryworld/2014/10/isotope-effect-produces-new-type-chemical-bond quote <<In the early 1980s it was proposed that in certain transition states consisting of a very light atom sandwiched between two heavy ones, the system would be stabilised not by conventional van der Waal’s forces, but by vibrational bonding, with the light atom shuttling between its two neighbours. However, despite several groups searching for such a system none was demonstrated and the hunt fizzled out. Now, Jörn Manz <http://www.chemie.fu-berlin.de/~manzwww/>, of the Free University of Berlin and Shanxi University in China, and colleagues believe they have the theoretical and experimental evidence to demonstrate a stable vibrational bond.>> On Fri, Jan 30, 2015 at 11:34 AM, H Veeder <hveeder...@gmail.com> wrote: > > New type of chemical bonddiscovered > http://www.sciencealert.com/new-type-of-chemical-bond-discovered > > Move over, covalent and ionic bonds, there’s a new chemical bond in town, > and it loves to shake things up. > > It’s taken decades to nail down, but researchers in Canada have finally > identified a new chemical bond, which they’re calling a ‘vibrational bond’. > > This vibrational bond seems to break the law of chemistry that states if > you increase the temperature, the rate of reaction will speed up. Back in > 1989, a team from the University of British Columbia investigated the > reactions of various elements to muonium (Mu) - a strange, hydrogen isotope > made up of an antimuon and an electron. They tried chlorine and fluorine > with muonium, and as they increased the heat, the reaction time sped up, > but when they tried bromine (br), a brownish-red toxic and corrosive > liquid, the reaction time sped up as the temperature decreased. The > researchers, Amy Nordrum writes for Scientific American, "were flummoxed”. > > Perhaps, thought one of the team, chemist Donald Flemming, when the > bromine and muonium made contact, they formed a transitional structure made > up of a lightweight atom flanked by two heavier atoms. And the structure > was joined not byvan der Waal’s forces - as would usually be expected - but > by some kind of temporary ‘vibrational’ bond that had been proposed several > years earlier. > > Nordrum explains: > > "In this scenario, the lightweight muonium atom would move rapidly between > two heavy bromine atoms, 'like a Ping Pong ball bouncing between two > bowling balls,' Fleming says. The oscillating atom would briefly hold the > two bromine atoms together and reduce the overall energy, and therefore > speed, of the reaction.” > > But back then, the team didn’t have the technology needed to actually see > this reaction take place, because it lasts for just a few milliseconds. But > now they do, and the team took their investigation to the nuclear > accelerator at Rutherford Appleton Laboratory in England. > > With the help of theoretical chemists from the Free University of Berlin > and Saitama University in Japan, Flemming’s team watched as the light > muonium and heavy bromine formed a temporary bond. “The lightest > isotopomer, BrMuBr, with Mu the muonium atom, alone exhibits vibrational > bonding in accord with its possible observation in a recent experiment on > the Mu + Br2 reaction,” the team reports in the journal Angewandte Chemie > International Edition. "Accordingly, BrMuBr is stabilised at the saddle > point of the potential energy surface due to a net decrease in vibrational > zero point energy that overcompensates the increase in potential energy.” > > In other words, the vibration in the bond decreased the total energy of > the BrMuBr structure, which means that even when the temperature was > increased, there was not enough energy to see an increase in the reaction > time. > > > *While the team only witnessed the vibrational bond occurring in a bromine > and muonium reaction, they suspect it can also be found in interactions > between lightweight and heavy atoms, where van der Waal’s forces are > assumed to be at play.* > "The work confirms that vibrational bonds - fleeting though they may be - > should be added to the list of known chemical bonds,” says Nordrum at > Scientific American. > > Sorry, future high school chemistry students, here's another thing you'll > probably have to rote learn. > > Source: Scientific American > > ----------- > > This link has a diagram of the potential energy curve for a vibrational > bond: > > > > A new type of chemical bond has been confirmed – the vibrational bond > > http://www.zmescience.com/science/chemistry/new-kind-chemical-vibrational-bond-0543543/ > > > > Harry > > >
