Hydroxonium cations

Summarizing all that has been said above concerning the structures of the octachloroditechnetates ( + 2.5), it may be concluded that their true composition is described by a formula with variable coefficients, namely M 6M"3-.,t(H30) [[Tc3Cl8] nH20, where x and n vary from 0 to 3. The substitution of some of the M ions by H30+ ions is possible by virtue of the similarity of the properties of the hydroxonium cation and the alkali metal cations both in solution and in the crystalline state [85,86],... 

Of special interest is the dehydration of polynuclear technetium bromide clusters, which contain hydroxonium cations with different numbers of hydration water molecules. Analysis of the results obtained leads us to conclude that at 140-200 °C dehydration occurs with a partial decomposition of the [H30(H20)3] + cations (30). 

Water thus causes the electrolytic dissociation of the hydrogen chlpride, which means the formation of a hydroxonium cation on one side and a chloride anion on the other side, so that the solution conducts electrical current. Ions of other acids are formed by analogical reaction with water. )... 

Such species would include the ammonium cation or the hydroxonium cation. These species will attract electrons Coulombically. Some species are both electron deficient and positively charged and so, not surprisingly, are very electrophilic. Suggest an example of such a species. 

One of the important assumptions in the above-outlined mechanism of ISE of electrolytes is that protons and hydroxyl anions have no eigenvolume in the dynamic system and do not experience exclusion from fine pores. If a charge is required at any point of the aqueous phase, a rapid shift of electrons along chains of hydrogen bonds between water molecules can easily convert any water molecule into a hydroxonium cation or hydroxyl anion. In this way electroneutraftty can easily be preserved in all micro-domains of the aqueous system. 

The crystalline dihydrate H4P,Ofi 2H,0 contains hydroxonium cations and should be formulated as 2H30-pH2P20s. 

Irrespective of how the cr-complex is formed from the adducts XLIV or XLIVb, it is not clear whether the anomalous selectivity phenomenon can be fully understood on the basis of the Olah hypothesis. Ab initio STO-3G calculations [155] on the structures LII and LIII, which model, respectively, the late and the early transition states of electrophilic substitution, i.e., of the (7- and 7c-complexes in the vicinity of those structures, have shown that both approximations lead to identical predictions in regard to positional selectivity. The structure LII is based on optimized geometry of the cyclohexadienyl cation, and in the structure LIII the hydroxonium cation has been selected as an electrophilic particle ... 

Any strong acid that may be present is first neutralised. Then, by selecting an appropriate base, whose conjugate acid has a Ka of about 10 5, the equilibrium for the tripositive cations will be forced to the right the base is too weak, however, to remove the hydroxonium ions from the equilibrium of the dipositive cations. Since a large excess of the basic ion is added, a basic salt of the tripositive metal usually precipitates instead of the normal hydroxide. Acetate or benzoate ions (in the form of the sodium salts) are the most common bases that are employed for this procedure. The precipitation of basic salts may be combined with precipitation from homogeneous solution, and thus very satisfactory separations may be obtained. 

Kwon and coworkers described solid polyelectrolyte complex systems which dissolve rapidly in response to small electric currents. The solid doses were based on poly(ethyl oxazoline) and poly(methacrylic acid) with a repeating unit stoichiometry of 1 1. Insulin was released in response to slight electric currents due to electrically induced polymer dissolution [380]. In similar work Kwon and coworkers [381] studied release of edrophonium chloride and hydrocortisone from poly(2-acrylamido-2-methylpropane sulfonate-co-n-butyl methacrylate). An on/oflf mechanism of the edrophonium chloride release was observed and was attributed to ion exchange of solute and hydroxonium ion. The cationic solute release was assisted by electrostatic forces, whereas release of the neutral hydrocortisone solute was only affected by swelling and deswelling. 

In reality H+, a bare proton, cannot exist alone except in isolation inside a high vacuum. The radius of H+ is about 1.5 x 10-15 m, which is 105 times smaller than other atoms. When H+ approaches another atom or molecule, it can distort the electron cloud of the latter. Therefore, other than in a gaseous ionic beam, H+ must be attached to another atom or molecule that possesses a lone pair of electrons. The proton as an acceptor can be stabilized as in pyramidal hydronium (or hydroxonium) ion H30+, tetrahedral NH4, and linear H2F+. These cations generally combine with various anions through ionic bonding to form salts. 

Propose the equation for the addition of a hydrogen cation to a water molecule to give a hydroxonium ion. 

Write the equation that represents the further addition of another hydrogen cation to the hydroxonium ion. Draw a dot and cross structure for the resultant ion. 

Of all the possible autoionisation products of water the best known cations are the hydroxonium, HsO, and the H502, species. These ions are commonly reported in the structure of solid acids but spectroscopically they have remained somewhat elusive. This stems not from an inability to recognise the presence of the ions from the overall spectral response but rather to produce specific and reliable assignments for individual features. Occasionally rather unusual species like the tetrahedral H30 (written (Ho.75)40 [22] or [23] have been... 

This atom contains just one electron in a Is orbital. In bonding with a second atom, it could behave in several ways. If it lost the electron, it could become a cation H+, i.e. a proton. However a proton is relatively very small and unstable as a single entity. In fact protons will not exist as such except in a discharge tube, but normally become attached to other molecules. An example of this is the attachment of a free proton to a water molecule in acid solution, to give the hydroxonium ion H30+. 

The nature of the hydrogen ion in water, which should more correctly be called the hydroxonium ion, H30+, is discussed below. The hydrogen ion in water is customarily referred to as the hydrogen ion, implying H30 +. The use of other terms, such as hydroxonium, is somewhat pedantic except in special cases. We shall usually write H+ for the hydrogen ion and assume it to be understood that the ion is aquated, since in a similar manner many other cations, Na+, Fe2 +, Zn2 +, etc., are customarily written as such, although there also it is understood that the actual species present in water are aquated species, for example [Fe(H20)6]2 +. ... 

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