Cation/molecule reactions

Anicich VG. An index of the literature for bimolecular gas phase cation-molecule reaction kinetics. JPL Publication U.S. (03-19) 2003. p. 1172... 

In Figure 7.13 examples of El, methane PICI and an interesting cation/molecule reaction called self-PICI are shown. Figure 7.13a is the 70 eV El spectrum of an aromatic compound in which the [M]+ cation (m/z 429) is not observed. For this molecule, the amount of internal energy retained by the [M]+ cation, after electron ionization, was so great that the [M]" " cation totally fragmented... 

Amine reagent gases such as ammonia and methylamine are the most common gases that produce characteristic and abundant cations for determining molecular weights. The following cation-molecule reactions describe the sequence of events, for ammonia, in the ion source (85) ... 

Anicich, V.G., 2003. An Index of the Literature for Bimolecular Gas Phase Cation-Molecule Reaction Kinetics. Jet Propulsion I-aboratory—California Institute of Technology, Pasadena, CA, USA, p.ll94, JPI--Ihiblication-03-19. 

The ECW equation does not apply to gas-phase cation affinities. According to Drago et al. [174], a transfer-energy component is significant in the enthalpy of cation/molecule reactions... 

Anicich, V. G. (2003) An index of the literature for bimolecular gas phase cation-molecule reaction kinetics. JPL Publication, Jet Propulsion Laboratory, Pasadena, CA, pp. 03-19. Yamada, N., Takahashi, J., and Sakata, K. (2002) The effect of cell-gas impurities and kinetic energy discrimination in an octopole collision cell ICP-MS under non-thermalised conditions. J. Anal. At. Spectrom., 17,1213-22. 

The controlled synthesis of polymers, as opposed to their undesired formation, is an area that has not received much academic interest. Most interest to date has been commercial, and focused on a narrow area the use ofchloroaluminate(III) ionic liquids for cationic polymerization reactions. The lack of publications in the area, together with the lack of detailed and useful synthetic information in the patent literature, places hurdles in front of those with limited loiowledge of ionic liquid technology who wish to employ it for polymerization studies. The expanding interest in ionic liquids as solvents for synthesis, most notably for the synthesis of discrete organic molecules, should stimulate interest in their use for polymer science. 

In view of the chemical nature of alkylaluminums and methyl halides, complexation is most likely to be rapid and complete, i. e. K is large. Indeed Me3 Al and a variety of Lewis bases were found to complex rapidly2. Initiation, i.e., f-butyl cation attack on monomer, is also rapid since it is an ion molecule reaction which requires very little activation energy. Thus, it appears that Rj t. and hence initiator reactivity are determined by the rate of displacement Ri and ionization R2. 

The ion-molecule reaction between thiirane and its radical cation to form a thiirane sulfide radical cation and ethylene has been studied by Qin, Meng and WiUiams [134]. ESR studies using a low-temperature sohd-state Freon radiolysis technique provided compeUing evidence that the hemibonded dimer radical cation of thiirane is an intermediate in this so-called sulfur-transfer reaction see Scheme 2. 

A new approach to improve the performance of solar devices using natural pigments is to employ carbon nanotube (CNT)-based counter-electrodes. As previously reported, the excited dye transfers an electron to Ti02 and so it acquires a positive charge. Then, the cationic molecule subtracts an electron from the counterelectrode which is transported by the electrolyte. This reaction is usually catalyzed by means of conductive and electrocatalytically active species for triiodide reduction of carbon coatings. CNTs have a high superficial area, which represents a very... 

There are basically two kinds of neutralization processes for the cation, reaction with the electron and with a negative ion. In each case, it may be assumed that neutralization will occur with the parent or fragment ion of lowest energy. It is believed that the various degradation processes for the cation-fragmentation, ion-molecule reaction, and so forth—are much faster than the neutralization process. In addition, one considers charge transfer, without decomposition, from the cation formally as a neutralization of that species. To effect that, of course, one... 

Solvent exchange reactions on metal cations are among the most simple chemical reactions a solvent molecule situated in the first coordination shell of the ion is replaced by another one, normally entering from the second shell. They are generally considered as fundamental reactions for metal ions in solution, since they constitute an important step in complex-formation reactions on metal cations. The reaction is... 

Once the tertiary cations have been formed, they can undergo electrophilic addition to alkene molecules (Reaction (4)). The addition is exothermic and contributes most of all the reaction steps to the overall heat of reaction. It has been proposed (24) that instead of the alkenes, the corresponding esters are added to the carbenium ions, restoring the acid in this way (Reaction (5)). The products of both potential steps are the same. 

If a compound is to be polymerizable cationically, the reaction site must be the most basic point in the molecule (unless the concentration of the catalyst exceeds that of the monomer). 

The reason is that these alleged kp values are mostly composite, comprising the rate constants of propagation of uncomplexed Pn+, paired Pn+ (Pn+A ), and Pn+ complexed with monomer or polymer or both, without or with an associated A" [17]. Even when we will eventually have genuine kp values for solvents other than PhN02, it will not be possible to draw many (or any ) very firm conclusions because the only theoretical treatments of the variation of rate constants with solvent polarity for (ion + molecule) reactions are concerned with spherically symmetrical ions, and the charge distribution in the cations of concern to us is anything but spherically symmetrical. 

We are being somewhat disingenuous here. If performed and interpreted correctly and with the appropriate ancillary phase-change enthalpy information, the enthalpy of formation of an arbitrary species by ion-molecule reaction chemistry and by combustion calorimetry must be the same. That the ionization potential of quinuclidine is higher than l,4-diazabicyclo[2.2.2]octane simply says that there is a stabilizing effect in the radical cation of the latter not found in the former. This information does not say that there is a stabilizing effect in the neutral molecular form of the latter not found in the former. After all, we trust the reader is not bothered by the fact that the ionization potential order of the cyclohexenes increases in the order 1,3-diene < 1,4-diene < 1-ene < 1,3,5-triene (benzene). 

Many other ion-molecule reactions involving highly unsaturated hydrocarbon ions and neutral olefins or the equivalent strained cycloalkanes have been studied by mass spectrometry98. For example, we may mention here the addition of ionized cyclopropane and cyclobutane to benzene radical cations giving the respective n-alkylbenzene ions but also isomeric cyclodiene ions such as ionized 8,9-dihydroindane and 9,10-dihydrotetralin, respectively. Extensive studies have been performed on the dimerization product of charged and neutral styrene4. 

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