A comparative ion chemistry study of acetone, diacetone alcohol, and mesityl oxide

Abstract

MARCH. Can. J. Chem. 64, 1979 (1986. The evolution of ion species by unimolecular and bimolecular reactions, both concurrent and sequential, haa been investigated for each of 2-propanone, d6-2-propanone, 4-hydroxy-4-methyl-2-pentanone, and 4-methyl-3-penten-2-one. Infrared multiphoton dissociation (IRMPD) has been used in order to differentiate between gaseous ionic isomers. It is concluded that the isomeric species, protonated 2-propanone dimer and protonated 4-hydroxy-4-methyl-2-pentanone, both of m / z 117, are of different structures. The ion species C6Hl10+ of m / z 99, and its perdeuterated analogue, which is observed in all three systems, may exist in two forms, one of which is unique to 2-propanone while an alternative form appears to be common to 4-hydroxy-4-methyl-2-pentanone and 4-methyl-3-penten-2-one. The ion species of m / z 83 (C5H70+) which is observed only in the latter two systems only could not be differentiated and may have a common structure. In the protonated dimers of 2-propanone and 4-hydroxy-4-methyl-2-pentanone, evidence obtained by IRMPD indicates that the activation energy for dedimerization (134 kJ molpl) is less than that for the dehydration process.AFAF KAMAR, ALEXANDER BALDWIN YOUNG et RAYMOND EVANS MARCH. Can. J. Chem. 64, 1979 (1986) On a CtudiC 1'Cvolution des especes ioniques provenant de reactions unimolCculaires ainsi que bimolCculaires, tant des rCactions qui se produisent d'une faqon concurente que ~Cquentielle, de la propanone-2, de la propanone-2-d6, de I'hydroxy-4 mCthyl-4 pentanone et de la mCthyl-4 pentene-3 one-2. Dans le but de distinguer les divers isomeres ioniques gazeux, on a fait appel la dissociation multiphotonique infrarouge (DMPIR). On en conclut que les especes isomeres dimeres protonCs de la propanone-2 et de l'hydroxy-4 mbthyl-4 pentanone-2 protonCe, de m / z = 117, possbdent deux structures diffkrentes. L'espece ionique C6H1,0+, de m / z = 99, et celle de son analogue perdeutCrC qui est observee dans les trois systemes peut exister sous deux formes; l'une est unique a la propanone-2 alors qu'une autre forme semble &tre commune a I'hydroxy-4 mCthyl-4 pentanone-2 et 2 la mCthyl-4 penthe-3 one-2. Les especes ioniques de m / s = 83 (C5H70+), qui ne sont observCes que dans les deux derniers systemes, ne presentent pas de diffkrences et possedent peut Ctre la m&me structure. Dans le cas des dimeres protonCs de la propanone-2 et de l'hydroxy-4 methyl-4 pentanone-2, on a obtenu des donnCes a l'aide de la DMPIR a l'effet que 1'Cnergie d'activation pour la dCdimCrisation (1 34 kJ mol-' ) est plus faible que celle requise pour le processus de deshydratation.[Traduit par la revue]

The effect of micellization on the EPR spectra and reactivity of 2,2,4,4-tetramethylpiperidinoxyl (TEMPO) radicals

“…The PA of a secondary alkyl ester, 2-propyl acetate, has been determined as 842.7 kJ/mol. [14] This value may be taken as a starting estimate for the PA of the carbonyl oxygen of the secondary alkyl esters 1a-f. It may increase with the alkanoyl chain length, in agreement with gas-phase measurements of PA's of methyl esters of fatty acids, reaching a maximum value of 864 kJ/mol.…”

Quadrupole ion traps

“…In the first IRMPD experiments in an ion trap using a CO 2 continuous wave laser, March and co-workers pursued studies of protonated aliphatic alcohol dimers, and their deuterated analogs were formed, isolated, and irradiated (Hughes, March, & Young, 1982;Hughes, March, & Young, 1983a,b,c). Subsequently, the dissociation rates of protonated aliphatic alcohol dimers were studied (Young, March, & Hughes, 1985), and the technique was extended to photodissociation of protonated species for isomer differentiation (Kamar, Young, & March, 1986b).…”

Glow Discharge Plasma Ionization Mass Spectrometry for Direct Detection of Oxygenated Organic Compounds in the Gas-phase

“…Ionization of the sample molecule would not be affected by moisture in the sample solvent after sample introduction. It was reported that the protonated dimer was observed for ketones if they were ionized, 25,41 and it is produced continuously with increasing the pressure by a reaction with M. 42,43 The proton added to the acetone dimer would be originated from ambient air, because the [2M+H] + at m/z = 129 can be observed for acetone-d6, and the discharge plasma can produce several cluster ions of the mass number at m/z = 55, 65, 73 and 83 as the proton source, as shown in Fig. S2(c).…”