Mass pentaquadrupoles

Unsaturated even-electron cations have been used in the gas phase to react with olefins, including dienes, in a way that characterizes their structure. In most cases, these ion/molecule reactions take place by [4 + 2] cycloadditions followed by specific elimination of even-electron neutrals. A most suitable instrumental setup for these studies are triple-quadrupole and pentaquadrupole mass spectrometers in which the ion/molecule addition reactions take place subsequent to the selection of the reagent ion. In most... 

Phosphitenylium cations have been postulated as intermediates in numerous reactions of 1-chlorophosphirenes including phosphirene complexes. Recently, the uncomplexed cation has been generated in the gas phase from 4 upon 70 eV electron ionization and its reactivity toward representative nucleophiles and dienes has been studied by pentaquadrupole mass spectrometry <20030BC395>. The first complex of a phosphirenylium cation 9 was prepared from 8 according to Scheme 5. The phosphirene complex 8 is rather unstable in neat or in solution and decomposes with the formation of the bisphosphirenyl ether 10 <19990M817>. 

Cooks and coworkers128 studied the Cl+ addition to aniline and other aromatic compounds via isolated NH3C1+, C1C=0+, protonated CH3C1, and Cl+ reagent ions using a pentaquadrupole mass spectrometer. The reactions of protonated monochloramine... 

Gas-phase synthesis of 3,4-dihydro-2,4-dioxo-277-l,3,5-oxadiazinium ions (16 X = Y = O) via cyclization of acylium (17 X = O) and thioacylium ions (17 X = S) with isocyanates (18 Y = O) and isothiocyanates (18 Y = S) has been investigated using tandem-in-space pentaquadrupole mass spectrometry (MS) <2005JAM1602>. The formation of single (19) and double (20) addition products in these reactions was observed to occur concurrently with proton transfer. The products of double addition have been observed to be favored in reactions with ethyl isocyanate, whereas the reactions with ethyl isothiocyanate formed preferentially either the single-addition product or proton-transfer products, or both. Furthermore, ab initio calculations at the Becke3LYP//6-311- -G(dp) level indicate that cyclization of the double addition products is favored and 3,4-dihydro-2,4-dioxo-277-l,3,5-oxadiazinium ions (16 X = Y = 0) are formed (Scheme 2) <2005JAM1602>. 

M. N. Eberlin, Triple-stage pentaquadrupole (QqQqQ) mass spectrometry and ion/molecule reactions. Mass Spectrom. Rev. 16, 113-144 (1997). 

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