HYDROGEN-BONDING IN TRANSIENT BIFUNCTIONAL HYPERVALENT RADICALS BY NEUTRALIZATION-REIONIZATION MASS-SPECTROMETRY

Neutralization-reionization mass spectrometry is used to generate hype rvalent 9-N-4 (ammonium) and 9-O-3 (oxonium) radicals derived from pro tonated alpha,omega-bis-(dimethylamino)alkanes and alpha,omega-dimetho xyalkanes, which exist as cyclic hydrogen-bonded structures in the gas phase. Collisional neutralization with dimethyl disulfide, trimethyla mine, and xenon of the hydrogen-bonded onium cations followed by reion ization with oxygen results in complete dissociation. Bond cleavages a t the hypervalent nitrogen atoms are found to follow the order CH2-N > CH3-N > N-H, which differs from that in the monofunctional hydrogen-n -heptyldimethylammonium radical, which gives CH2-N > N-H > CH3-N. No o verall stabilization through hydrogen bonding of the bifunctional hype rvalent ammonium and oxonium radicals is observed. Subtle effects of r ing size are found that tend to stabilize large ring structures and ar e attributed to intramolecular hydrogen bonding.