Diacidic Bases

In a solution of a diacidic base, the following equitibria are established  

The determination of the five variables chjB, t HB-. Ch30+ nd coh requires five independent equations. These are the equations of the law of mass actions of aU protolysis reactions and the equations for charge and amount balances  

1 Diacidic Base with a Strong and a Weak Protolysis Reaction 

A good example for such base is the sulfide ion (p/sTbi =0.1 andpATb2 = 7.0). First, a high concentration is considered Fig. 54 depicts the pH-logCj diagram of a solution containing 0.1 mol Na2S. 

From the diagram follows that the pH should be read slightly to the right of the pH-coordinate of Pj, as on the left side of Pj the sum of HB, HsO, and H2B is always larger than the concentration of OH ions. The diagram further tells that in this range the concentrations of HsO and H2B are much smaller than the concentration of HB, so that it is a good approximation to write  

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Neutralization. In water, lime ionizes readily to Ca ", Mg ", and OH , forming a strong base or alkaU. Both Ca(OH)2 and Mg(OH)2 are strong diacid bases neutralizing such strong monobasic acids as HCl and HNO, yielding neutral salts and heat. 

Quinidine is alkaline in solution and behaves as a diacidic base forming two series of salts. The neutral sulphate, Bj. H2SO4.2HjO, crystallises from hot water in colourless prisms, soluble in water (1 in 98 to 100 at 15°, or 1 in 7 at 100°), more so in alcohol or chloroform, and scarcely in ether. It is dextrorotatory, [a]D +184-17° (CHCI3). The acid sulphate, B. H2SO4.4H2O, forms hair-like, colourless needles, soluble in 8-7 parts of water at 10° + 247-8° (c = M/10, HjO) or + 256-4° (c = M/40,... 

It is sparingly soluble in ether or chloroform, readily in alcohol or solutions of caustic alkalis, but not in ammonia, and gives the thalleioquin reaction. Cupreine is a diacidic base the neutral sulphate, Bj. H2SO4, forms colourless anhydrous needles, m.p. 257 , soluble in 813 parts of water at 17 the iwiid sulphate, B. HjSO. HjO, crystallises in prisms and is soluble in... 

Although the exact composition was and still is regarded as only tentative, all the subsequent evidence showed that the formula is at least approximately correct. In particular, ample proof will be found that the substance is a diacidic base. 

The acidity of a base is the number of hydroxy ions formed per molecule of the base in aqueous solution. It may also be considered as the number of H+ ions that can be accepted by one molecule of the base. Thus, NaOH and KOH are monoacid bases, Ca(OH)2 and Mg(OH)2 are diacid bases, and Al(OH)3 and Fe(OH)3 are triacid bases. 

Piguet, V., Gu, F., Foti, M., Demaurex, N., Gruenberg, J.-L. and Carpentier, J, and Trono, D. (1999). Nef-induced CD4 degradation a diacidic-based motif in Nef functions as a lysosomal targeting signal through the binding of /3-COP in endosomes. Cell 97, 63-73. 

Korenman, I.M. and Nikolaev. Determination of the protonation constants of weak diacidic bases by an extraction methods, Zh. Phys. Chem., 48 2545-2549, 1974. 

Oxyarionio Bam.— These bodies, which are diacid bases, are obtained by the slow oxidation of the tertiary monar-... 

Iodoso-compounds behave as diacid bases, e.g., C6H5I(OH)2, which combine with acids to form salts (Preparation 466). Reducing agents or... 

The nitric acid of the original 2 mols of ammonium nitrate is exactly sufficient for the formation of 2 mols of guanidine nitrate. But the intermediate biguanide is a strong diacid base the ammonium nitrate involved in its formation supplies only one equivalent of nitric acid and there is a point during the early part of the process when the biguanide mononitrate tends to attack the unchanged ammonium nitrate and to liberate ammonia from it. For this reason the process works best if a small excess of... 

G. Bredig,1 and R. Bach concluded that while the first acidic function is nearly the same as that of ammonium hydroxide, the second acidic function of the base is so weak in aq. soln. that the corresponding salts are almost completely hydrolyzed. T. Curtius and H. Schulz said that a dihydrate exists in aq. soln. because the cryoscopic data gave a mol. wt. of 68. These data, however, can be interpreted on the basis either of a monohydrate or of a dihydrate. All this, does not decide whether hydrazine is a monoacidic or a diacidic base. E. C. Gilbert also found that in the electrometric titration of a 0-lM-soln. of hydrazine hydrate... 

In the absence of special transport mechanisms (which is not proven, see further in the text), the vacuolar accumulation ratios (VAR) could be predicted from a derivation of the Hendelson-Hasselbach equation using the calculated log/) values. Indeed, for a diacidic base, the log D is a function of the acidity constants (pka) and the partition coefficient (log P) ... 

Cmchonamine, C Hg4N20, wh, rhmb ndls (from ale), mp 184-94°. An alkaloid which may be obtd, by extraction, from the bark of Remijia Purdie-anna. Being a strong diacidic base, it forms well defined salts, such as nitrate, (which is practically insol in w) (Refs 1 2), nitrite and picrate (Ref 1)... 

Diethyl octadecanedioate can be prepared by the same stoichiometry provided that the diester is dissolved in four times as much alcohol (4 X 30 ml.), that the saponification step is performed at 60°C., and that the final mixture of diacid and half ester is resolved in hexane. The modified procedure yields ethyl hydrogen octadecanedioate melting at 71.5° to 72.5°C. in agreement with the literature value (I). Yields based upon the amount of diester consumed are 90.0% half ester and 3.3% diacid. Based upon the amount of diester used, they are 44.4% half ester, 1.6% diacid and 51.0% recovered diester. 

In an investigation of the protonation of weak bases and second protonation of diacidic bases, Katritzky and co-workers obtained a value of — 4.51 for the Ho value of half-protonation of the quinazoline cation. The value is... 

Diacid-based linkers, such as the succinic linker 21, have been described to prepare alcohols. The procedure involves the esterification of the starting alcohol with succinic anhydride and DMAP to yield the hemiester that is anchored to an amino containing-resin by means of an amide bond. The bound alcohol is then elaborated and finally released with a nucleophile. Oligosaccharides have been assembled following this approach and released with aqueous ammonia or sodium methoxide in methanol-dioxane [73, 74]. Peptide alcohols have also been prepared with the succinic linker on BHA resin and released by treatment with NH3 in MeOH for 72-96h or hydrazine in DMF for 24h [75]. Similarly, hydroquinone-0,0 -diacetic acid (linker 22) has been used to link nucleosides to polystyrene or CPG supports. Cleavage of oligonucleotides was carried out with aqueous ammonia [76]. Other diacids with a similar function have also been described [77]. 

VIII) may be briefly summarized as follows. Villalstonine is a dimeric, diacidic base, which contains one methoxycarbonyl group, two methyl-imino groups, and an ethylidene group. Its UV spectrum is consistent with the presence of indole and dihydroindole chromophores containing no substituents in the benzene rings. Alkali fusion yields 2-methylindole, indole 2-carboxylic acid, and a /3-carboline derivative selenium dehydrogenation also affords a j8-carboline derivative, so far unidentified. Acid hydrolysis of villalstonine yields pleiocarpamine (XV), one of the alkaloids of Pleiocarpa mutica Benth. 

A solution of sodium carbonate is prepared by dissolving 0.212 g Na2C03 and diluting to 100 mL. Calculate the normality of the solution (a) if it is used as a monoacidic base, and (b) if it is used as a diacidic base. 

Dipole moment 1.83-1.90. Dielectric constant (25 ) 51.7. Latent heal of fusion (mp) 3.025 kcal/mole latent heat of vaporization (bp) 9760 kcal/mole (calc), Crit temp 38Forms salts with inorganic acids. Highly polar solvent. Powerful reducing agent. Dissolves many inorganic substances. Misc with water, methyl, ethyl, propyl, isobutyl alcohols. Forms an azeotropic mixture with water, bp 40 120.3°, which contains 55 mole-% (68.5 weight-%) NjH,. LD,g in mice (mg/kg) 57 i.v. 59 orally (Witkin),... 

Optically inactive, diacidic base. Isolated as the dipicrate dihydrate, C),HMN,20,8.2H,0, yellow needles from water, dec 283-284 (becomes anhydrous in vacua at S6 > dec 284-285 ). 

The fact that the monomethylene derivative above only forms a monoquaternary salt may be contrasted with the fact that the diphosphine (PhaP)2CH2 forms a diquaternary salt and that the phosphino-phosphazene, Ph2P(=NC6H4X)-CHaPPha (X = H, p-Br, p-Me, m-Me, p-OMe, or m,p-NOa), is preferentially quaternized at the tervalent phosphorus atom. The basicities and quaternization behaviour of these compounds were examined and it was shown that the diphosphazenes [PhaP(=NC6-H4X)]aCH2 are diacid bases, whereas the diphosphines such as (PhaP)2CH2 are monoacid bases. Some of these features are also discussed in an extensive review of the base properties of monophosphazenes, both from chemical and physical standpoints. 

The formation of a monobenzoyl derivative and a mononitroso derivative, b.p. 176°/4 mm., [a]u — 155° (no solvent) shows that anabasine is a secondary-tertiary diacidic base. This conclusion is substantiated by the formation of an A-methylanabasine, b.p. 268°, when the base is heated with formaldehyde and formic acid (420). With potassium permanganate anabasine is oxidized to nicotinic acid whereas dehydrogenation either with silver acetate or with zinc dust causes the loss of six hydrogen atoms and the formation of 3, 2-dipyridyl, b.p. 293-294° (picrate, m.p. 151-152°)(423). These experiments support structure CLXXIV previously applied to anabasine (399), a formulation that is confirmed by the following experiments. When A-benzoylanabasine methiodide is oxidized with potassium ferricyanide, the 7V-benzoyl derivative of the corresponding pyridone,... 

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