Oxonium compound

Oxonium Compounds. An addition or double compd of an organic oxide with strong acids or their salts, as, R20.HX (Refs 5 7)... 

OXONIUM COMPOUNDS, TRIETHYLOXO-NIUM PLUOBORATE, 46,113 OXONIUM COMPOUNDS, TRIMETHYLOXO-NIUM PLUOBORATE, 46, 120 OXONIUM COMPOUNDS, TRIMETHYLOXO-NIUM 2,4,6-TRINITROBENZENE-SULPONATE, 46, 122... 

The polymerisation of (I) has been studied over a wide temperature range, in bulk and in solution, and with several different catalysts. All these are protonic acids, or metal halides, or carbonium, carboxonium, or oxonium compounds. None of the cyclic formals tested can be polymerised by radicals or anions. 

The oxonium compound then ionizes H30Br H30 +Br, and the H30 -ion loses its charge at the cathode during electrolysis and forms hydrogen and water. 

Additive compounds are formed with aniline, piperazine, hexamethylenetetramine and quinoline 8 with pyridine, the two compounds, AsC13. C5H5N (m.pt. 138-9° C.) and AsC13.2CbHsN (m.pt. 61° C.), have been isolated.9 Addition of arsenic trichloride to dry 1 4-dioxan gives an oxonium compound, (C4H802)3.2AsC13 (m.pt. 62° C.).10... 

Metallic halide salts. The present state of knowkdgt < nu-oeming reactions of epoxides with metallic halide salts is due in Jhj g< measure to the work of MoorwcJn and oo-workers1131-1UI in the fielil of oxonium compounds. 

OXONIUM COMPOUNDS. Coordination compounds, commonly of certain oxygen-containing organic substances, with mineral acids, of the general type [R 0]HCI. These compounds bear a strong resemblance to the oxonium (hydronium) ion, which is a proton in combination with a water molecule, and is the form in which protons commonly exist in aqueous solutions. 

TRIMETHYLOXONIUM FLUOBORATE (Oxonium compounds, trimethyloxonium tetrafluoroborate)... 

Ether, in which the solubility is 220 gA at 20°, is intermediate between the other two classes of solvents, owing to the formation of the oxonium compound. 

Interestingly, the trifluoromethyl oxonium compound is deshielded relative to the analogous ether, whereas those of the sulfonium CF3 groups are actually shielded compared to the simple sulfides. 

It has been found recently that nitrogen dioxide forms addition products with compounds having an ether bond in the molecule (i.e. oxygen, which readily yields oxonium compounds) and for example, with ethyl ether, N204.2(C2H5)20 (m. p. -74.8°C), and with dioxane, tetrahydrofuran and tetrahydropyran (Rubin, Sisler and Shechter [57]). 

Diazinium, oxazinium, and thiazinium cations possess a pyridine-like nitrogen atom, but it is of very weak basicity and nucleophilicity. However, pyridazines do form diquaternary salts with very strong alkylating agents such as oxonium compounds. Electrophilic attack at ring carbon in these compounds is practically unknown. These trends are emphasized in cationic rings with an increased number of nitrogen atoms. 

On account of the greater electronegativity of oxygen compared with nitrogen, oxonium compounds are produced much more rarely than ammonium compounds as a result of the positive charge which the central atom thereby formally obtains. 

ESMS was employed to identify reactive intermediates in the enantioselective hydrogenation of ethyl pyruvate on Pt-alumina, Pt black, and Pt black+alumina catalysts modified by dihydrocinchonidine in acetic acid [56]. The ESMS spectra of the raw product revealed a large number of species which fell into four groups (1) dihydrocinchonidine and its hydrogenated derivatives (2) the adducts of ethyl pyruvate and its oligomers (3) (R)-ethyl lactate, the product of the enantioselective hydrogenation, and its adducts and (4) oxonium compounds formed from alumina. The latter most likely play a decisive role in the development of the chiral environment of the catalyst surface. As suggested by the authors, these oxonium cations could make the so-called electrostatic catalysis [57],based on electrostatic acceleration, possible. 

Cyclic oxonium compounds generated from hemiacetals by a Lewis acid react with 2-silyloxythiophene to produce useful intermediates via C-C bond formation (Scheme 58). This reaction has been extensively used to prepare a large number of synthetic analogs of acetogenins, which are effective antitumor agents (Scheme 59) <2000CSR109>. 

Oxonium compounds are well known, especially in the field of super acids where traces of water are immediately converted to compounds like H3OAsF6 [132], The formation of such salts is most easily understood as H20 replacing the weaker base HF from H2F+ cations present in solutions of strong Lewis acids in anhydrous hydrogen fluoride (aHF). 

Quite recently oxonium compounds of d-block transition metals and also closely related complexes of the lanthanides were isolated for the first time. In general, the solvent is aHF, and a strong Lewis acid, preferably AsFs, is added to the solution or suspension of an appropriate metal compound. Water may be introduced in various ways, e.g. using hydrated starting material, dissolution of metal oxides or even through the addition of H-.OAsFg. Some examples of reactions leading to new oxonium fluorometallates are collected in Table 4. 

Trivalent positive oxygen is present in oxonium compounds water, for example, possesses an affinity for a proton amounting to i8o kcals and thus the hydrogen ion H3O+ has the following structures ... 

The Kekul constant valence Formula VIII, which viewed oxonium compounds as molecular compounds formed by adding acid to an organic... 

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