Salt-molecule reaction

The matrix isolation technique has been applied, in conjunction with the salt/molecule reaction technique, to model the high temperature gas phase reactions of alkali halide salt molecules. The reactions with Lewis acids such as SiFi, HF and CO2 yielded ion pair products which were quenched into inert matrices for spectroscopic study. Difficulties arising from lattice energy considerations in alkali halide salt reactions are minimized by the initial vaporization of the salt reactant. The reaction of such salt molecules with Lewis bases, including H2O and NH3, yielded complexes similar in nature to transition metal coordination complexes, with binding through the alkali metal cation to the base lone pair. 

The application of the salt/molecule reaction technique to the study of reactions with Lewis bases such as H2O and NH3 presents the possibility for a different type of interaction which may find some cinalogy in transition metal coordination chemistry. The structure of small complexes such as MX H20 are of considerable interest both experimentally and theoretically. These studies were initiated as a result of the observation of several beinds in the spectrum of alkali halide salts in argon which could not readily be assigned to the isolated salt species. Rather, it was shown that these bands were due to reaction of the salt with impurity H2O, which was always present in these experiments to some degree. A study was then initiated to investigate these beinds, and the nature of the reaction conplex. 

Salt/molecule reactions with fluoride acceptors or Lewis acids appear, in all cases studied to date, to form ion pair complexes as the initial reaction product for such Lewis acids as HF, SiFi, BF3 and COF2. There has been no evidence of abstraction as the initial step, although some systems may exist where this step will be preferred. Some spectroscopic effects of ion pairing are observed in the spectra of the product anions, but these still allow for the study of imusual anions in a relatively unperturbed environment. 

Salt-Molecule Reaction. Tevault and Nakamoto [131] carried out matrix cocondensation reactions of metal salts such as PbF2 with L(CO, NO and N2) in Ar, and confirmed the formation of PbF2-L adducts by observing the shifts of IR bands of both components. These spectra are shown in Fig. 3.67 (of Sec. 3.18.6). 

Ault and coworkers have utilized salt-molecule reactions to produce a number of novel triatomic and other anions in isolated environments [411]. For example, the linear symmetric [FHF] ion was produced in Ar matrices via codeposition of CsF vapor with HF gas diluted in Ar [399] ... 

Matrix isolation spectroscopy has provided structural information that is unique to XY4-type molecules in inert gas environments. For example, the symmetry of the anions in Cs BF4 and Cs PF4 formed via salt-molecule reactions in Ar matrices are lowered to in the former, and to a Symmetry no higher than C2v, in the latter [920]. 

Calcium sulfate, the substance used to absorb water in desiccators, provides an example of this temperature sensitivity. Anhydrous calcium sulfate absorbs water vapor from the atmosphere to give the hydrated salt. The reaction has a negative AS° because water molecules become more constrained when gaseous water molecules move into the solid state. The reaction also has a negative AH ° because of the electrical forces of attraction... 

The NaCl -SOD formed during these reactions can be clearly identified by its IR spectrum, perchlorate sodalite collapse at 1050°C. From the thermo gravimetric analysis it is evident that at this temperature the entire amount of NaCl escapes. The degree of the cage filling by salt molecules can be calculated on the basis of both the oxygen and the NaCl loss. 

The high ionic concentration at the micellar surface may result in an ionic strength effect on reaction rate. Salt effects in water, however, are generally smaller for ion-molecule reactions than for reactions which involve an increase or decrease of charge, and they should be approximately zero in the... 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

In the presence of copper(I) salts in acidic media o-ethynyl-benzaldehyde derivatives were found to cycloisomerise to 2-benzopyrylium salts (4.26.), The reaction, although working in the absence of catalyst too, was accelerated by the addition of different metal salts. The reaction was applied in the preparation of azaphilones and related molecules.30... 

Several studies on the reactions and preparation of aziridines have been published. The ring opening of 2-substituted aziridines, accomplished by first converting them into aziridinium salts by reaction with a benzyl bromide and then attack of the bromide counter ion, gave only one bromide in a regio- and stereo-specific reaction.43 Since attack by the bromide ion of the aziridinium salt only occurred at the most substituted carbon with an inversion of stereochemistry, it was concluded the reaction occurred by an SN2 mechanism. This was supported by calculations at the MPWBlK/6-31+G(d) level of theory for reactions featuring two solvating acetonitrile molecules embedded in an acetonitrile matrix. 

Atoms or ions combine in chemical reactions to make molecules, metal alloys, or salts. Chemical reactions can also involve changing one molecule into a different molecule or breaking one molecule down into smaller molecules, atoms, or ions. 

In order to parallel solution-phase reactivity and ion-molecule reactions in the gas phase, the reactivity of a typical homogeneous catalyst, described earlier by Grubbs and co-workers [128], was studied by ESMS [129]. Electrospray of the dichloride salt of 15 and increasing the collisional activation potential first yielded predominantly the monocation 16, but with raising the tube lens potential even higher the intensity of 16 decreased due to loss of the second phosphine ligand, loss of trimethylamine, and loss of HCl. The observed fragmentation pattern was consistent with the assumed structure of the ruthenium complex. 

The heat of formation of NF + ton is estimated at 245 20 kcal./mole from thermochemical correlations and from failure to detect NF4+ as product of an ion-molecule reaction between NFS+ and NFS in a mass spectrometer. The ion NF3H+ was detected as a product of a related reaction under similar conditions its heat of formation appears to be less than 225 kcal./mole. Estimates of the heat of formation of some salts of NF4+ have been made by means of the Kapus-tinskii approximation for lattice energies. For this purpose a correlation was developed between known thermochemical radii9 of tetrahedral ions and their van der Wools radii. It is concluded that the perchlorate, sulfate, and fluoride salts will be unstable relative to likely decomposition products. 

The red PlttP salt is stable in air and soluble in CH2C12 and MeCN. The nitrido oxo cation NUO+ has been identified in the gas phase by mass spectra it was obtained by ion-molecule reactions from U+. 

Besides saturated 1,5-diketones, unsaturated 1,5-diketones can also, in some cases, be converted into thiopyrylium salts. The reaction of aryl substituted 2,4-dichloro-2-pentene-1,5-diones (87) with HjS and HCIO4 in a mixture of AcOH and AC2O leads to the formation of 3-chlorothiopyrylium perchlorates 88-90. It should be noted that under the same conditions l,3,5-triphenyl-2-pentene-l,5-dione is converted quantitatively into the corresponding pyrylium salt 8. The pentenediones not containing chlorine atoms in the molecule evidently do not react with H2S under the conditions of acid catalysis as a result of the fact that the cyclization rate for them significantly exceeds the addition rate of H2S (90ZOR1904). 

Robinson, 1969a). It is probable that the hydrophobic nature of the phenyl groups of p-nitrophenyl diphenyl phosphate results in deep penetration of the neutral ester in the Stern layer, thus shielding the phosphoryl group from nucleophilic attack. Unlike other reactions between nucleophiles and neutral substrates catalyzed by cationic micelles (Bunton and Robinson, 1968, 1969a) and the hydrolysis of dinitrophenyl phosphate dianions in the presence of cationic micelles (Bunton et al., 1968), the catalysis of the hydrolysis of -nitrophenyl diphenyl phosphate by CTAB arises from an increase in the activation entropy rather than from a decrease in the enthalpy of activation. The Arrhenius parameters for the micelle-catalyzed and inhibited reactions are most probably manifestations of the extensive solubilization of this substrate. However, these parameters can be composites of those for the micellar and non-micellar reactions and the eifects of temperature on the micelles themselves are not known. Interpretation of the factors which affect these parameters must therefore be carried out with caution. In addition, the inhibition of the micelle-catalyzed reactions by added electrolytes has been observed (Bunton and Robinson, 1969a Bunton et al., 1969, 1970) and, as in the cases of other anion-molecule reactions and the heterolysis of dinitrophenyl phosphate dianions, can be reasonably attributed to the exclusion of the nucleophile by the anion of the added salt. 

When powders of metal oxides are stirred in solvent such as an acid-phosphate solution, they dissolve slowly in the solvent and release cations in the solution. These cations react with the phosphate anions within the solvent and form a precipitate of salt molecules. Under the right conditions, these molecules form an ordered structure and grow into crystals. This ordered crystalline solid of the reaction products is the CBPC. Thus, CBPC formation is a result of the following three steps ... 

A second class of chemical compounds whose reactions are catalyzed by the fluoride ion, and by CsF are organosilanes (42). The diversity of chemistry exhibited by these compounds is considerable, and with the potential for expanded valence in these compounds to five and six coordinate intermediate anions, the application of the salt/molecule technique was suggested. The gas phase ion/molecule reactions of several silane systems have been investigated through ion cyclotron resonance techniques (53,54), providing thermochemical information about the product ions in these systems. Perhaps the simplest reaction is that of F with SiFi, the intermediate anion SiFs has been stabilized under carefully controlled circumstances (55), while the 2 1 adduct SiFe is well known ( ). Less is known about the effects of alkylation on the stability of the product ions. 

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