A compendium of gas phase basicity and proton affinity measurements

Abstract

Numerical values of experimental measurements, calculations and estimations of gas phase basicities and proton affinites are presented.Where appropriate they are recalculated to common values for the proton affinity of ammonia and the heat of formation of the proton. The annotated information is ordered by molecular formula following the Hill System.Indices are given to permit location of information by numerical value of the measurement (s) , the compound formula, name and synonym, and CAS Registry Number. The literature coverage is essentially complete through 1977.

Is the atmospheric pressure chemical ionisation and collisionally induced methanol loss from protonated dehydroamino acids a retrosynthetic process?

“…However, it must be stressed that previous investigations12,13 of the chemical ionisation mass spectrometry of cyclic β ‐amino alcohols have shown that, despite the considerable difference in proton affinities exhibited by amino and hydroxy groups, both basic centres can be protonated in a competitive way and hence the process is kinetically controlled. In the present case (compounds 2 and 4 ), amide and ester groups are present and, given the small difference in the measured PA values of these two groups [e.g., PA(CH 3 COOCH 3 ) = 194 kcal/mol, PA(CH 3 CONH 2 ) = 205 kcal/mol],14 protonation is expected to occur on both basic sites.…”

Determination of salvinorins and divinatorins in Salvia divinorum leaves by liquid chromatography/multistage mass spectrometry

“…The elimination of a water molecule may be at first sight more difficult to explain. However, if we assume that the protonation site is very likely located on the ether oxygen of the lactone ring of the molecule, characterized by a more favourable proton affinity value in respect to the oxygen atoms present in the other substituent groups of the molecule,15 a rearrangement involving the donation of an hydrogen of the ring to the charge site allows the subsequent water elimination and a concerted ring contraction (rH and rD mechanisms following the nomenclature of McLafferty16).…”

The gas phase reactivity of the dimethylchloronium ion with alkylbenzenes

“…Although the latter value is not available, proton affinity for the methylbenzenes appears to increase monotonically with the number of methyl groups (15). Calculation suggests that ipso-protonated toluene is -6 kcal mol-I less stable than the para-protonated form but that such differences decrease with increasing alkyl substitution on the ring (16).…”