ISSN:
0947-3440
Schlagwort(e):
Basicity
;
Imine protonation
;
Solvent effect
;
Steric shielding
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The protonation state of N-(1,1,3,3-tetramethyl-2-indanylidene)methylamine (5/6) is assessed on the basis of fully assigned 1H- and 13C-NMR spectra in [D8]toluene and in CDCl3. In either solvent the basicity of 5 remains intermediate between those of pyridine (weaker) and triethylamine (stronger). Nearly complete proton transfer to 5 in toluene occurs with trifluoroacetic and dichloroacetic acids, whereas partial protonation is achieved by chloroacetic acid or acetic acid and even by biphenyl-2,2′-diol (7). As a possible model for imine protonation in the hydrophobic region of proteins like the rhodopsins, the sterically shielded iminium cation 6 (or 2) does not require solvation by a polar solvent; rather it can be stabilized in toluene solution by a counteranion whose proton affinity is diminished by an assisting hydrogen bond.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jlac.199519950251
