956239-94-4Relevant academic research and scientific papers
Structures of transient species in the photochromic reaction of 1',3',3'-trimethylspiro: time-resolved resonance Raman study of isotopically substituted analogues
Yuzawa, Tetsuro,Ebihara, Ken,Hiura, Hidefumi,Ohzeki, Tomoyuki,Takahashi, Hiroaki
, p. 1487 - 1498 (1994)
Time-resolved resonance Raman spectra of seven kinds of isotopically substituted analogues of 1',3',3'-trimethylspiro in the photomerocyanine form have disclosed that only the vibrations of the cleaved benzopyran part are re
Low-energy collision-induced fragmentation of negative ions derived from ortho-, meta-, and para-hydroxyphenyl carbaldehydes, ketones, and related compounds
Attygalle, Athula B.,Ruzicka, Josef,Varughese, Deepu,Bialecki, Jason B.,Jafri, Sayed
, p. 1207 - 1217 (2008/03/11)
Collision-induced dissociation (CID) mass spectra of anions derived from several hydroxyphenyl carbaldehydes and ketones were recorded and mechanistically rationalized. For example, the spectrum of m/z 121 ion of deprotonated ortho-hydroxybenzaldehyde shows an intense peak at m/z 93 for a loss of carbon monoxide attributable to an ortho-effect mediated by a charge-directed heterolytic fragmentation mechanism. In contrast, the m/z 121 ion derived from meta and para isomers undergoes a charge-remote homolytic cleavage to eliminate an ?H and form a distonic anion radical, which eventually loses CO to produce a peak at m/z 92. In fact, for the para isomer, this two-step homolytic mechanism is the most dominant fragmentation pathway. The spectrum of the meta isomer on the other hand, shows two predominant peaks at m/z 92 and 93 representing both homolytic and heterolytic fragmentations, respectively. 18O-isotope-labeling studies confirmed that the oxygen in the CO molecule that is eliminated from the anion of meta-hydroxybenzaldehyde originates from either the aldehydic or the phenolic group. In contrast, anions of ortho-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde, both of which show two consecutive CO eliminations, specifically lose the carbonyl oxygen first, followed by that of the phenolic group. Anions from 2-hydroxyphenyl alkyl ketones lose a ketene by a hydrogen transfer predominantly from the α position. Interestingly, a very significant charge-remote 1,4-elimination of a H2 molecule was observed from the anion derived from 2,4-dihydroxybenzaldehyde. For this mechanism to operate, a labile hydrogen atom should be available on the hydroxyl group adjacent to the carbaldehyde functionality. Copyright
