Hydroxide ion solution

In contrast, the acidity function approach, which involves a study of the dependence of the ionisation ratio ([S ]/[HS]) on an appropriate acidity function, was recently used for substituted acetophenones and some aliphatic ketones (Cockerill et al., 1974 Earls et al., 1975 Kankaanpera et al., 1978). All these studies used the property that the addition of DMSO increases the basicity of aqueous hydroxide ion solutions p/ s values were determined from (46) by plotting the ionisation ratio versus the H acidity function for... 

Bordwell and his co-workers discovered that the formation of the pseudo-base from nitromethane in hydroxide ion solutions (Equation 21) has a Pf of 1.28 and a p q of 0.83 giving rise to an a/ of 1.54. Similarly the ttf values for reaction of bases with other nitroalkanes are greater than unity also violating the Leffler assumption. 

Is hydrogen more easily produced from I M hydrogen ion solution, from I M hydroxide ion solution, or from pure water ... 

The first clear example of activation of a phosphate exclusively by this mode was the reaction involving intermolecular attack of hydroxide ion on trimethylphosphate (TMP) coordinated to the pentaamminciridium(III) moiety (75). This complex was chosen because the Ir-0 bond is not readily broken and survives the reaction at the P center. The reaction of the free TMP in hydroxide ion solution presumably occurs by direct attack of hydroxide ion on the P center to give the five-coordinate oxyphosphorane and ultimately methanol and dimethylphosphate. Similarly, the reaction of the complex occurs exclusively by attack of OH" at the P center yielding finally dimethylphosphatopentaammineiridium(III) ion and methanol, as shown by an tracer experiment. Both reactions have the same rate law ... 

The hydrolysis of ethylene phosphate in hydroxide ion solution proceeds with a rate constant of 5 x 10" L-mol" s" (100). The O-P-0 angle in the ring of ethylene phosphate of 99° is expected to be rather similar to that for the four-membered ring incorporating the cobalt and phosphorus centers. Therefore it is likely that reaction at the strained P center of the complex is eclipsed by a more rapid metal-ligand cleavage reaction. This problem can be circumvented by the use of metal ion complexes of Ir(III) where the metal-ligand bonds are more inert as the locus for the reaction. 

With the above arguments in mind the reactivity of two pentaam-mineiridium(III) phosphodiester complexes was investigated (79a). The first of these, the ethyl-4-nitrophenylphosphate complex, [(NH3)5lrENPPp, hydrolyzed in aqueous hydroxide ion solution by a reaction consisting of two paths, both paths yielded the same products. The reaction obeyed the rate law ... 

The rate constants for the reaction were ki = 2.4 x 10 L-mol s and k2 = 2.9 X 10 L mol" s Both paths produced two phosphorus containing metal complexes in the same relative yields. The minor species (19% yield) was readily identified as the ethylphosphate complex [(NH3)5lrEP]. The major species, however, was not the chelate phos-phoramidate ester, but the ring opened species, N-coordinated monoden-tate ethylphosphoramidate, 14. Both products were indefinitely stable in hydroxide ion solution. The reaction proceeds some 10 -fold slower than the reaction of the analogous Co(IIl) complex, which is rather significant and will be discussed in detail later. The slower rate of production of the... 

Textbooks tell students that "ferrous hydroxide is a pale green solid." As Eugene Rochow pointed out during the 1978 McMaster Conference(6), the dry recital of memorized fact is what killed the "old" descriptive chemistry. Anyway, pure ferrous hydroxide is not pale green, it is white. But when one mixes ferrous and hydroxide ion solutions in the open air, the precipitated green ferrous hydroxide darkens rapidly to a black color, and eventually becomes the familiar red-orange hydrated ferric oxide. This phenomenon raises many questions, all answerable experimentally ... 

Armstrong, R.D., Fleischmann, M. and Thirsk, H.R. (1966) Anodic behaviour of mercury in hydroxide ion solutions. Journal of Elect roanalytical Chemistry, 11, 208. 

Abyaneh, M.Y. (2004) Kinetics of single-phase electrocrystallization processes II CTTs due to the model of growth of hyperboloids. Journal of the Electrochemical Society, 151, C743. Armstrong, R.D., Fleischmann, M., and Thirsk, H.R. (1966) Anodic behaviour of mercury in hydroxide ion solutions. Journal of Electroanalytical Chemistry, 11, 208. 

One anomaly inmrediately obvious from table A2.4.2 is the much higher mobilities of the proton and hydroxide ions than expected from even the most approximate estimates of their ionic radii. The origin of this behaviour lies in the way hr which these ions can be acconmrodated into the water structure described above. Free protons cannot exist as such in aqueous solution the very small radius of the proton would lead to an enomrous electric field that would polarize any molecule, and in an aqueous solution the proton inmrediately... 

When either hydrogen ions or hydroxide ions participate in a redox half-reaction, then clearly the redox potential is alTected by change of pH. Manganate(Vir) ions are usually used in well-acidified solution, where (as we shall see in detail later) they oxidise chlorine ions. If the pH is increased to make the solution only mildly acidic (pH = 3-6), the redox potential changes from 1.52 V to about 1.1 V, and chloride is not oxidised. This fact is of practical use in a mixture of iodide and chloride ions in mildly acid solution. manganate(VII) oxidises only iodide addition of acid causes oxidation of chloride to proceed. 

Aqueous ammonia can also behave as a weak base giving hydroxide ions in solution. However, addition of aqueous ammonia to a solution of a cation which normally forms an insoluble hydroxide may not always precipitate the latter, because (a) the ammonia may form a complex ammine with the cation and (b) because the concentration of hydroxide ions available in aqueous ammonia may be insufficient to exceed the solubility product of the cation hydroxide. Effects (a) and (b) may operate simultaneously. The hydroxyl ion concentration of aqueous ammonia can be further reduced by the addition of ammonium chloride hence this mixture can be used to precipitate the hydroxides of, for example, aluminium and chrom-ium(III) but not nickel(II) or cobalt(II). 

The liberated iodine is titrated with standard sodium thiosulphate(Vr) solution after acidification to remove the hydroxide ions. 

Cobaltill) hydroxide is obtained as a precipitate when hydroxide ion is added to a solution containing cobalt(II) ions. The precipitate is often blue, but becomes pink on standing it dissolves in excess alkali to give the blue [CofOH) ion, and in slightly alkaline solution is easily oxidis by air to a brown solid of corttposition Co "0(OH). 

The reactions of aqueous solutions of nickel(II) salts with hydroxide ions, with excess ammonia, with sulphide ion and with dimethyl-glyoxime (see above) all provide useful tests for nickel(II) ions. 

Mercury(II) oxide, HgO, occurs in both yellow and red forms the yellow form is precipitated by addition of hydroxide ion to a solution containing mercury(II) ions, and becomes red on heating. Mercury(II) oxide loses oxygen on heating. 

In the strongly basic medium, the reactant is the phenoxide ion high nucleophilic activity at the ortho and para positions is provided through the electromeric shifts indicated. The above scheme indicates theorpara substitution is similar. The intermediate o-hydroxybenzal chloride anion (I) may react either with a hydroxide ion or with water to give the anion of salicyl-aldehyde (II), or with phenoxide ion or with phenol to give the anion of the diphenylacetal of salicylaldehyde (III). Both these anions are stable in basic solution. Upon acidification (III) is hydrolysed to salicylaldehyde and phenol this probably accounts for the recovery of much unreacted phenol from the reaction. 

The production of benzyl benzoate from benzaldehyde, which may be isolated under special conditions (low temperature and absence of excess of alkali), is explained by assuming that when some benzyloxide ions (CgHj—CHjO s RCH O ) are formed in the alkaline solution, these can replace hydroxide ions thus ... 

Perhaps the most extensively studied catalytic reaction in acpreous solutions is the metal-ion catalysed hydrolysis of carboxylate esters, phosphate esters , phosphate diesters, amides and nittiles". Inspired by hydrolytic metalloenzymes, a multitude of different metal-ion complexes have been prepared and analysed with respect to their hydrolytic activity. Unfortunately, the exact mechanism by which these complexes operate is not completely clarified. The most important role of the catalyst is coordination of a hydroxide ion that is acting as a nucleophile. The extent of activation of tire substrate througji coordination to the Lewis-acidic metal centre is still unclear and probably varies from one substrate to another. For monodentate substrates this interaction is not very efficient. Only a few quantitative studies have been published. Chan et al. reported an equilibrium constant for coordination of the amide carbonyl group of... 

According to the Arrhenius definitions an acid ionizes m water to pro duce protons (H" ) and a base produces hydroxide ions (HO ) The strength of an acid is given by its equilibrium constant for ionization m aqueous solution... 

The role of the basic catalyst (HO ) is to increase the rate of the nucleophilic addi tion step Hydroxide ion the nucleophile m the base catalyzed reaction is much more reactive than a water molecule the nucleophile m neutral solutions... 

The concentration of hydroxide ion is too small in acid solution to be chemically significant... 

Strong and Weak Bases Just as the acidity of an aqueous solution is a measure of the concentration of the hydronium ion, H3O+, the basicity of an aqueous solution is a measure of the concentration of the hydroxide ion, OH . The most common example of a strong base is an alkali metal hydroxide, such as sodium hydroxide, which completely dissociates to produce the hydroxide ion. 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cycHzed mbber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenoHc stmcture renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxyHc acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubiHty is controUed by chemical and polarity differences rather than molecular size. 

This reaction, conducted in alkaline solution, also produces carboxyl groups by hydrolysis of the amide (54). Recent work on the reaction of polyacrylamide with hydroxylamine indicates that maximum conversion to the hydroxamate fiinctionahty (—CONHOH) takes place at a pH > 12 (57). Apparendy, this reaction of hydroxylamine at high pH, where it is a free base, is faster than the hydrolysis of the amide by hydroxide ion. Previous studies on the reaction of hydroxylamine with low molecular weight amides indicated that a pH about 6.5 was optimum (55). 

Hydroxide ions [14280-30-9] are released by the resin as anions are adsorbed from the Hquid phase. The effect is elimination of acidity in the Hquid and conversion of the resin to a salt form. Typically, the resin is restored to the OH form with a 4% solution of NaOH. 

Although reasonably stable at room temperature under neutral conditions, tri- and tetrametaphosphate ions readily hydrolyze in strongly acidic or basic solution via polyphosphate intermediates. The hydrolysis is first-order under constant pH. Small cycHc phosphates, in particular trimetaphosphate, undergo hydrolysis via nucleophilic attack by hydroxide ion to yield tripolyphosphate. The ring strain also makes these stmctures susceptible to nucleophilic ring opening by other nucleophiles. 

Aqueous ammonia also acts as a base precipitating metallic hydroxides from solutions of their salts, and in forming complex ions in the presence of excess ammonia. For example, using copper sulfate solution, cupric hydroxide, which is at first precipitated, redissolves in excess ammonia because of the formation of the complex tetramminecopper(TT) ion. 

The reducing-end units (see Fig. 8) are highly labile in alkaline solutions. After an initial attack by hydroxide ions at the hemiacetal function, C-1, a series of enoHzations and rearrangements leads to deoxy acids, ie, saccharinic acids, and fragmentation. Substituents on one or more hydroxyl groups influence the direction, rate, and products of reaction. 

Silicates in Solutions. The distribution of sdicate species in aqueous sodium sdicate solutions has long been of interest because of the wide variations in properties that these solutions exhibit with different moduli (23—25). Early work led to a dual-nature description of sdicates as solutions composed of hydroxide ions, sodium ions, coUoidal sdicic acid, and so-called crystaHoidal sdica (26). CrystaHoidal sdica was assumed to be analogous to the simple species then thought to be the components of crystalline sdicate compounds. These include charged aggregates of unit sdicate stmctures and sdica (ionic micelles), and weU-defined sdicate anions. 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

Cadmium Hydroxide. Cd(OH)2 [21041-95-2] is best prepared by addition of cadmium nitrate solution to a boiling solution of sodium or potassium hydroxide. The crystals adopt the layered stmcture of Cdl2 there is contact between hydroxide ions of adjacent layers. Cd(OH)2 can be dehydrated to the oxide by gende heating to 200°C it absorbs CO2 from the air forming the basic carbonate. It is soluble ia dilute acids and solutions of ammonium ions, ferric chloride, alkah haUdes, cyanides, and thiocyanates forming complex ions. 

The hydrolysis of (eq. 4) and the addition of less than equivalent amounts of hydroxide ion to aqueous solutions of, followed by aging,... 

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