Infrared multiple‐photon dissociation spectroscopy of deprotonated 6‐hydroxynicotinic acid

Abstract

The deprotonated, 6-pyridone structure is confirmed by comparison of the infrared multiple-photon photodissociation (IRMPD) spectrum in the region of 1100-1900 cm(-1) with those predicted using DFT and MP2 calculations.

Breslow Intermediates (Amino Enols) and Their Keto Tautomers: First Gas‐Phase Characterization by IR Ion Spectroscopy

“…The calculated barrier height for the transformation from K‐24 to E‐24 is 283 kJ mol −1 , in line with the experimental observation. Similar cases of nonthermal behavior have previously been reported [24–26] . A prominent example is ergothionein, a 2‐mercaptohistidine trimethyl betaine, which preferably adopts a thione tautomeric ion structure in MeOH solution, which is also carried over to and identified in the gas phase [27] …”

“…Similarc ases of nonthermal behavior have previously been reported. [24][25][26] Ap rominente xample is ergothionein, a2 -mercaptohistidine trimethyl betaine, which preferably adopts at hione tautomeric ion structure in MeOH solution,w hichi sa lso carried over to and identified in the gas phase. [27] Unfortunately,n oc rystals of the ketone K-24 suitable for Xray structural analysisc ould be obtained thus far.H owever,t he reaction of the triazolin-5-ylidene C-2 with the three alkyl-substitutedb enzaldehydes A-5,6,7 shown in Scheme 6y ielded crystalline adducts that could be analyzed by single-crystal XRD.…”

Hydrogen tunneling avoided: enol-formation from a charge-tagged phenyl pyruvic acid derivative evidenced by tandem-MS, IR ion spectroscopy and theory

“…Carry-over effects of solution-phase favored ion structures into the gas phase, which are there kinetically trapped after the electrospray process, have been observed and reported numerous times. [26][27][28] In a previous study on the thione-thiol tautomeric equilibrium of ergothionein (2-mercaptohistidine trimethylbetaine, ET), we found clear evidence that cationic molecular ions of ET conserve their condensed-phase ground state, i.e. a thione ion structure in the gas phase.…”

Stereospecific collision-induced dissociation and vibrational spectroscopy of protonated cyclo (Tyr-Pro)

“…[115,[120][121][122] Including a continuum solvation model considerably modifies the energy ordering compared to the gas phase. [123] To test whether it could be the case for the system studied here as well, we have conducted calculations using a continuum solvation model. [124] The energy difference between the three experimentally observed c-LLH + conformers is reduced to 0.9 kcal/mol in aqueous solution, much smaller than in the gas phase.…”