ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The liquid secondary ion mass spectrometry and electron impact ionization fragmentation pathways of 1,9-bis(dimethylamino)-2,8-dimethoxy-dibenzofuran (1), a new proton-sponge base with increased steric compression (buttressing) and much higher basicity (pKa = 14.3), and of its monoprotonated (2) and monodeuterated (3) salts were invetigated in a collision-induced dissociation (CID) tandem mass spectrometric study supported by unimolecular linked scans at constant B/E, CID mass-analysed ion kinetic energy spectra and accurate mass measurements. They show an ‘extended’ proximity effect, involving the stepwise participation of all the four functional groups, in addition to the ‘normal’ proximity effect involving loss of Me2NH and H·. The behaviour of 1 appears to differ in some ways from that of its protonated (2) or deuterated (3) salts. The unprecedented observation of the maintenance of the hydrogen (or deuterium) bridge under soft ionization in the salts of very strong proton-sponge bases, which show buttressing effects in solution, is strong experimental support for the conservation of these buttressing effects in the gas phase, where the protonated (or deuterated) cations of salts such as 2 (or 3) are very stable, H+ (or D+) being completely ‘sequestered.’
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210280504
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