Weak bases salts

Formazans behave as weak acids as well as weak bases. Salts of formazans have been isolated.26,334,335 The acid dissociation constants of some substituted formazans have been determined from their solution spectra.336... 

Scherrer observed [280,281], as have others [161,162,275], that for a large number of ordinary charged species partitioning into octanol in the presence of aqueous solutions containing 0.15 M KC1 or NaCl, weak-acid salts have values of diff(k)g PN ) equal to 4, and that weak-base salts have cliff values equal to 3. These are helpful numbers to keep in mind when predicting the values of log P1 when log PN is known. 

Figure 4.1 shows that the solubility is a maximum at pH ,ax- This occurs because, at this pH, the solution is saturated in both the weak base salt species and the neutral species that is, the solubility is controlled by both the solubility product and the neutral species intrinsic solubility. According to Equation (4.17) an increase in cation concentration gives an increase in the pH of maximum solubility (a decrease in H ax ). 

Converts weak base salt solution to salt/base mixture plus pure acid... 

Example 19-3 Weak Base/Salt of Weak Base Biffir Solution... 

Red needles from EtOH. Mp, 303-6 . Spar. sol. EtOH. Insol. H2O. Weak base. Salts hyd. by H2O. Cone. HgSO — > pale yellow sol.. ... 

The type of viscosity of a (partially) neutralised carbomer hydrogel is plastic a (large) yield value and a decreasing viscosity with increasing shear stress a carbomer gel is not thixotropic (see Sect. 18.2). Carbomer hydrogel is not compatible with a number of active substances because of the pH (about 6.5) that is needed for the gel formation. For instance salicylic acid is ionised at this pH and hence not effective as a keratolytic. Weak base salts (e.g. alkaloid, chlorhexidine, aluminium and zinc salts) will precipitate at this pH. 

We can derive a relationship for [OH ] in a solution containing a weak base, B, plus a Band BH+ represent the weak base salt that contains the cation, BH, of the weak base, just as we did for weak acids. In general and its conjugate acid, respectively—... 

PMMA molding compounds are resistant to water, weak acids, dilute aqueous solutions of strong acids, weak bases, salt solutions, aliphatic hydrocarbons, fats, and oils. It should be noted that PMMA is resistant to weak acids or dilute aqueous solutions of strong acids only at low temperatures. PMMA is also not very resistant to potassium or sodium hydroxide solutions above 20 °C [86]. 

The sodium ethanoate which is largely dissociated, serves as a source of ethanoate ions, which combine with any hydrogen ions which may be added to the solution to yield more of the acid. The addition of hydrogen ions has therefore much less effect on such a solution than it would have on water. In a similar manner, the solution of the salt of a strong acid and a weak base, in the presence of a weak base, has a pH that is insensitive to additions of alkali. 

Conversion of the salt of a weak base into the free base e.g.y if... 

Conversion of the salt of a weak base into the free base. Prepare a column of a strong base anion resin (such as Amberlite IRA-40o(OH) ) washed with distilled water as above. Drain off most of the water and then allow 100 ml. of A//2.Na.2C03 solution to pass through the column at 5 ml. per minute. Again wash the column with 200 ml. of distilled water. Dissolve 0-05 g. of aniline hydrochloride in 100 ml. of distilled water and pass the solution down the column. The effluent contains aniline in solution and free from all other ions. 

Aminoazobenzene is a very weak base, and consequently it will not form salts with weak organic acids, such as acetic acid, although it will do so with the strong mineral acids, such as hydrochloric acid. Aminoazobenzene is a yellowish-brown compound, whilst the hydrochloride is steel blue. The colour of the latter is presumably due to the addition of the proton to the phenyl-N-atom, the cation thus having benzenoid and quinonoid forms ... 

Aniline hydrochloride, being a salt formed from a very weak base and a strong acid, undergoes considerable hydrolysis in aqueous solution to aniline... 

The amines are comparatively weak bases, so that a certain amount of free amine will be produced by salt hydrolysis unless an excess of acid is present. The reaction mixture must be kept very cold during the process (which is exothermic in character), otherwise the diazonium salt may be partially converted into the corresponding hydroxy compound ... 

As early as 1889 Walker (320), using samples of thiazole, 2,4-dimethylthiazoie, pyridine, and 2,6-dimethylpyridine obtained from Hantzsch s laboratory, measured the electrical conductivity of their chlorhydrates and compared them with those of salts of other weak bases, especially quinoline and 2-methylquinoline. He observed the following order of decreasing proton affinity (basicity) quinaldine>2,6-dimethyl-pyridine>quinoline>pyridine>2,4-dimethylthiazole> thiazole, and concluded that the replacement of a nuclear H-atom by a methyl group enhanced the basicity of the aza-aromatic substrates. 

Equation 6.44 is written in terms of the concentrations of CH3COOH and CH3COO- at equilibrium. A more useful relationship relates the buffer s pH to the initial concentrations of weak acid and weak base. A general buffer equation can be derived by considering the following reactions for a weak acid, HA, and the salt of its conjugate weak base, NaA. 

Trifluoromethylpyridine can be prepared ia 54% yield from picolinic acid and sulfur tetrafluoride—hydrogen fluoride (434). 2-Trifluoromethylpyridine is a weak base no hydrochloride salt is formed. However, 2-trifluoromethylpyridine 1-oxide [22253-71-0] (bp 132—133°C/2.7 kPa (20 mm Hg)) is prepared ia 81% yield usiag 30% hydrogen peroxide—acetic acid (438). 

Weak base resins when in the free base (hydroxyl) form are not capable of splitting neutral salts such as sodium chloride. Salt forms of weak base resins release anions to the Hquid phase if other ions for which the resin has a greater selectivity are present. 

Aminophenols and their derivatives are of commercial importance, both in their own right and as intermediates in the photographic, pharmaceutical, and chemical dye industries. They are amphoteric and can behave either as weak acids or weak bases, but the basic character usually predominates. 3-Aminophenol (2) is fairly stable in air unlike 2-aminophenol (1) and 4-aminophenol (3) which easily undergo oxidation to colored products. The former are generally converted to their acid salts, whereas 4-amiaophenol is usually formulated with low concentrations of antioxidants which act as inhibitors against undesired oxidation. 

Physical Properties. Both (1) and (2) are weak bases, showing 4.94 and 5.40, respectively. Their facile formation of crystalline salts with either inorganic or organic acids and complexes with Lewis acids is in each case of considerable interest. Selected physical data for quinoline and isoquinoline are given in Table 1. Reference 4 greatly expands the range of data treated and adds to them substantially. 

Hydrolysis is the interaction of the ion or ions of a salt with water to produce a weak acid, weak base, or both. When a metal hydroxide is brought into equihbrium with water the following occurs ... 

Hand in hand with this research on finding a suitable carboxyUc acid chemical for cross-linker has been the search for an economical catalyst system. The catalyst found to be most effective for the esterification reaction was sodium hypophosphite (NaH2P02). This material was also costiy and out of range for the textile industry. Because weak bases function as catalyst, a range of bases has been explored, including the sodium salts of acids such as malic acid. 

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