Unusual protonic species

The stable 2-norbornyl cation has recently been shown to be a non-classical, unusually stabilized species. Olah et al. (1970) proved spectroscopically that this ion is a comer-protonated nortricyclene with a pentavalent carbon atom. The value for the carbonylation-decarbonyla-tion equilibrium constant K (= of the 2-norbomyl ion illustrates... 

After briefly reviewing the spectral consequences that result for the formation of H-bonds ( 9.1) the extensive body of work on water is presented ( 9.2), including water in minerals ( 9.2.1), its protonated species ( 9.2.2), the ices ( 9.2.3) and water at bio-interfaces ( 9.2.4). The next section ( 9.3) covers proton transfer, which is important for systems, across all the scientific disciplines from Materials Science to Biology. This section includes the dicarboxylates as models ( 9.3.1), proton conductors ( 9.3.2) and unusual species ( 9.3.3). 

In the area of trivalent phosphorus acid chemistry some very unusual reactions have been reported from combinations of 4-dimethylamino-pyridine (DMAP) with phosphorus trichloride. In one case a phosphide and free chlorine are claimed to be formed The extreme nucleofugicity of a tervalent phosphorus atom bearing two DMAP groups also stimulates an unprecedented Arbusov reaction of a tervalent derivative. Another surprise is that, although the reaction is certainly acid-catalysed, the mechanism of substitution at phosphoramidites does not involve either P- or N-protonated species. A final surprise in this area is the preparation, by Russian chemists, of some tervalent phosphorus compounds which apparently contain P-OH groups. 

QCISD(T)]. Such size binding energies are indicative of almost regular covalent bonding, similar to the protonated species. As noted above, both the H" " and M binding energies to C(H2) in diazomethane are unusually large. 

The (9-acyl isourea is activated by protonation at the imine nitrogen. This site is unusually basic because of resonance stabilization in the protonated species, not unlike the situation encountered in the case of the guanidino group (Section 26-1). The resulting protonated urea substituent is an excellent leaving group. We can then write an addition-elimination sequence for the attack of the amine on the carbonyl carbon to eventually furnish the amide. 

What makes FHF an attractive species to investigate by nmr spectroscopy is that it consists of three nuceli each with spin 1/2 bonded directly. Also, the proton of the strong hydrogen bond should have an unusual chemical shift. Early work failed to detect the expected F doublet and H triplets (e.g. Soriano et al., 1969), and it was not until the importance of the solvent was appreciated that coupling was observed (Fujiwara and Martin, 1971, 1974a,b). Suitable media were found to be the dipolar aprotic solvents acetonitrile, nitromethane and dimethylformamide. 

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