Ion-combination reaction

The volumes of activation for some additions of anionic nucleophiles to arenediazonium ions were determined by Isaacs et al. (1987) and are listed in Table 6-1. All but one are negative, although one expects — and knows from various other reactions between cations and anions — that ion combination reactions should have positive volumes of activation by reason of solvent relaxation as charges become neutralized. The authors present various interpretations, one of which seems to be plausible, namely that a C — N—N bond-bending deformation of the diazonium ion occurs before the transition state of the addition is reached (Scheme 6-2). This bondbending is expected to bring about a decrease in resonance interaction in the arenediazonium ion and hence a charge concentration on Np and an increase in solvation. 

Absorbance based indicators are known to undergo either ion combination reactions (such as with protons, cations, or anions) or oxidation-reduction reactions31-43. 

It appears that the ion-combination reactions make little or no contribution to the formation of hydrogen100,114. This is reasonable, since clustered H2X+ and X-H-X" ions would be expected to reform HX, viz. 

In the same research described in Problem 8, the authors also examined the rate of Reaction (F) in pure water and in NaCl solution to guarantee that the ionic surfactants were not displaying an electrolyte activity effect as is ordinarily observed with ion combination reactions. For 10-5 M crystal violet and 0.01 M NaOH, they observed the following ... 

Use these data and the Debye-Hiickel theory of electrolyte nonideality to criticize or defend the following proposition Indifferent electrolytes always inhibit the rates of ion combination reactions because the activity coefficients are fractions. The data for CTABr show an enhancement of rate so this cannot be due to an activity effect. In these data, the k s for pure water and aqueous NaCl are essentially identical, so no activity effects operate in the absence of micelles either. 

OXIDATION AND REDUCTION All the reactions mentioned in the previous sections were ion-combination reactions, where the oxidation number (valency) of the reacting species did not change. There are however a number of reactions in which the state of oxidation changes, accompanied by the interchange of electrons between the reactants. These are called oxidation-reduction reactions or, in short, redox reactions. 

The endpoint may be detected by addition of colored indicators, provided the indicator itself is not electroactive. Potentiometric and spectrophotometric indication is used in acid-base and oxidation-reduction titrations. Amperometric procedures are applicable to oxidation-reduction and ion-combination reactions especially for dilute solutions. 

Ion combination reactions. In these reactions, ions simply change partners. In the reaction of NaCl with AgNOs, the products are AgCl and NaN03. 

The products of many of these reactions can be predicted by using the solubility rules. Ion-combination reactions that form precipitates (water-insoluble compounds) are known as precipitation reactions. In the reaction above, only AgQ is insolnble (solnbility rule 3) and precipitates as soon as the reactants are mixed... 

The underline of PbS04 reveals that this compound precipitates out of solution. Notice also that the first reaction is an acid-base reaction and the second is an ion combination reaction. The addition of sulfate ion to the dissolved smithsonite would not produce a precipitate. 

An ion-combination reaction occurs when the cation (positively charged ion) from one reactant combines with the anion (negatively charged ion) from another to form a particular kind of product compound. The conventional equation is a double-replacement type in which the ions appear to change partners AX + BY —> AY + BX. In this section, the product is an insoluble ionic compound that settles to the bottom of... 

In every ion-combination reaction considered so far, it has been assumed that both reactants are in solution. This is not always the case. Sometimes the description of the reaction will indicate that a reactant is a solid, liquid, or gas, even though it may be soluble in water. In such a case, write the correct state symbol after the formula in the conventional equation and carry the formula through all three equations unchanged. 

Redox reaction, ion-combination reaction, precipitation reaction, molecule-formation reaction, neutralization reaction... 

A precipitation reaction is an ion-combination reaction that yields an insoluble ionic compound. A molecule-formation reaction is an ion-combination reaction that yields a molecular product, usually water or a weak add. If the product of an ion-combination reaction is water, formed by the reaction of an acid and a hydroxide base, the reaction is a neutralization reaction. 

A one-pot conversion of benzyl alcohols to benzyl fluorides by treatment of the alcohols with a combination of methanesulfonyl fluoride, cesium fluoride and 18-crown 6 ether in tetrahydrofuran has been repotted The reaction involves mesylation of the alcohols followed by cleavage of the resultant mesyl esters with a fluoride ion The reaction has been extended also to certain heterocycles bearing the N hydroxymethyl group [43] (equation 31)... 

In type A reaction soluble sulfide ions combine with metal ions to form a precipitate of insoluble metal sulfide. Sulfur s oxidation state of minus two does not change in this reaction. The reaction is... 

Precipitation reactions, like all reactions, reach a position of equilibrium. Suppose, for example, solutions of Sr(N03)2 and K2Cr04 are mixed. In this case, Sr2+ ions combine with Cr042- ions to form a yellow precipitate of strontium chromate, SrCr04 (Figure 16.1). Very quickly, an equilibrium is established between the solid and the corresponding ions in solution ... 

The net ionic equation shows that Ag+ ions combine with Cl ions to precipitate as solid silver chloride, AgCl (see Fig. 1.5). A net ionic equation focuses our attention on the change that results from the chemical reaction. 

In APCI, droplets are generated by a combination of heat and a nebulizing gas. While the analytes are embedded in a droplet, and thus protected to some extent from the heat, many thermally labile materials are decomposed. In addition, ionization occurs mainly by ion-molecule reactions and yields predominantly singly charged ions. If, therefore, compounds do not undergo thermal degradation, a mass spectrometer with extended mass range would be required to detect any ions formed. 

Aerospray An atmospheric-pressure ionization technique in which droplets are formed from a liquid stream by a combination of heat and a nebulizing gas and ions are formed by ion evaporation ramer man ion-molecule reactions. 

The simplest balanced chemical equation for a precipitation reaction is a net ionic equation that has ions as the reactants and a neutral solid as the product. In a precipitation reaction, reactant ions combine to form a neutral ionic solid. One reactant carries positive charge and the other carries negative charge, but the product is electrically neutral. Because electrical charge always is conserved, the total positive charge of the reacting cations... 

As mentioned in the introduction, it is difficult to explain the characteristics of the oscillation based on the mechanisms which have been proposed so far for the potential oscillations with systems similar to Eq. (16) [4,7,35-38]. A precise investigation on individual ion transfers and adsorptions at two interfaces is necessary for the elucidation of the oscillation mechanism, although the spontaneous oscillation might be realized by the combination of a much larger number of ion transfer reactions and adsorptions than those in the case of the oscillation under the applied potential or current. 

LC-APCI-MS is a derivative of discharge-assisted thermospray, where the eluent is ionised at atmospheric pressure. In an atmospheric pressure chemical ionisation (APCI) interface, the column effluent is nebulised, e.g. by pneumatic or thermospray nebulisation, into a heated tube, which vaporises nearly all of the solvent. The solvent vapour acts as a reagent gas and enters the APCI source, where ions are generated with the help of electrons from a corona discharge source. The analytes are ionised by common gas-phase ion-molecule reactions, such as proton transfer. This is the second-most common LC-MS interface in use today (despite its recent introduction) and most manufacturers offer a combined ESI/APCI source. LC-APCI-MS interfaces are easy to operate, robust and do not require extensive optimisation of experimental parameters. They can be used with a wide variety of solvent compositions, including pure aqueous solvents, and with liquid flow-rates up to 2mLmin-1. 

This entire reaction is reversed when the blood reaches the lungs. Because carbon dioxide is eliminated by ventilation, the reaction is pulled to the left. Bicarbonate ions diffuse back into the red blood cells. The hemoglobin releases the hydrogen ions and is now available to load up with oxygen. The bicarbonate ions combine with the hydrogen ions to form carbonic acid, which then dissociates into carbon dioxide and water. The carbon dioxide diffuses down its concentration gradient from the blood into the alveoli and is exhaled. A summary of the three mechanisms by which carbon dioxide is transported in the blood is illustrated in Figure 17.8. 

The above examples should suffice to show how ion-molecule, dissociative recombination, and neutral-neutral reactions combine to form a variety of small species. Once neutral species are produced, they are destroyed by ion-molecule and neutral-neutral reactions. Stable species such as water and ammonia are depleted only via ion-molecule reactions. The dominant reactive ions in model calculations are the species HCO+, H3, H30+, He+, C+, and H+ many of then-reactions have been studied in the laboratory.41 Radicals such as OH can also be depleted via neutral-neutral reactions with atoms (see reactions 13, 15, 16) and, according to recent measurements, by selected reactions with stable species as well.18 Another loss mechanism in interstellar clouds is adsorption onto dust particles. Still another is photodestruction caused by ultraviolet photons produced when secondary electrons from cosmic ray-induced ionization excite H2, which subsequently fluoresces.42... 

Even though ions are lost as the reaction proceeds, due to H+ and OH- ions combining to form water, there are still plenty of Na+ and Cl- ions remaining in the solution to cause the indicator bulb to glow brightly, but not quite as brightly as the initial solution. 

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