Strong base number

Strong Base Number or Value is the amount of acid, expressed as mg of equivalent KOH, used to neutralize the strong basic constituents of 1 g of the sample. 

Treatment of geminal dihalocyclopropyl compounds with a strong base such as butyl lithium has been for several years the most versatile method for cumulenes. The dihalo compounds are easily obtained by addition of dihalocarbenes to double--bond systems If the dihalocyclopropanes are reacted at low temperatures with alkyllithium, a cyclopropane carbenoid is formed, which in general decomposes above -40 to -50°C to afford the cumulene. Although at present a number of alternative methods are available , the above-mentioned synthesis is the only suitable one for cyclic cumulenes [e.g. 1,2-cyclononadiene and 1,2,3-cyclodecatriene] and substituted non-cyclic cumulenes [e.g. (CH3)2C=C=C=C(CH3)2]. 

ThiO 4-oxoselenazolidines substituted in the 3-position, have been described in a number of patents, (79, 80). They are used as intermediates in the manufacture of pharmaceuttcal products and color sensitizers in photography. They are obtained by action of isothiocyanates on a-hydroselenoacetic acid in the presence of strong base and in the absence of air (Scheme 77). 

In an acid-base reaction, the reaction unit is the proton. For an acid, the number of reaction units is given by the number of protons that can be donated to the base and for a base, the number of reaction units is the number of protons that the base can accept from the acid. In the reaction between H3PO4 and NaOH, for example, the weak acid H3PO4 can donate all three of its protons to NaOH, whereas the strong base NaOH can accept one proton. Thus, we write... 

Bell has calculated Hq values with fair accuracy by assuming that the increase in acidity in strongly acid solutions is due to hydration of hydrogen ions and that the hydration number is 4. The addition of neutral salts to acid solutions produces a marked increase in acidity, and this too is probably a hydration effect in the main. Critchfield and Johnson have made use of this salt effect to titrate very weak bases in concentrated aqueous salt solutions. The addition of DMSO to aqueous solutions of strong bases increases the alkalinity of the solutions. 

Here again, K is a very large number the reaction of acetic acid with a strong base goes essentially to completion. 

The concentration of the acid is usually of the order 0.05-0.2 mol L" Similar remarks apply to weak bases. It is clear that the greater the concentrations of acid and conjugate base in a buffer solution, the greater will be the buffer capacity. A quantitative measure of buffer capacity is given by the number of moles of strong base required to change the pH of 1 litre of the solution by 1 pH unit. 

The theory of titrations between weak acids and strong bases is dealt with in Section 10.13, and is usually applicable to both monoprotic and polyprotic acids (Section 10.16). But for determinations carried out in aqueous solutions it is not normally possible to differentiate easily between the end points for the individual carboxylic acid groups in diprotic acids, such as succinic acid, as the dissociation constants are too close together. In these cases the end points for titrations with sodium hydroxide correspond to neutralisation of all the acidic groups. As some organic acids can be obtained in very high states of purity, sufficiently sharp end points can be obtained to justify their use as standards, e.g. benzoic acid and succinic acid (Section 10.28). The titration procedure described in this section can be used to determine the relative molecular mass (R.M.M.) of a pure carboxylic acid (if the number of acidic groups is known) or the purity of an acid of known R.M.M. 

Step 3 Write the chemical equation for the neutralization reaction and use the reaction stoichiometry to find the amount of H. O ions (or OH ions if the analyte is a strong base) that remains in the analyte solution after all the added titrant reacts. Each mole of H30+ ions reacts with 1 mol OH ions therefore, subtract the number of moles of H30+ or OH ions that have reacted from the initial number of moles. 

The whole range of carboxylic acids and alcohols can be reacted to form esters. They are found in a large number of natural and synthetic scents and perfumes because of their pleasant odor. Many are used as solvents for paints and resins. Esters are converted back into the original acids and alcohols hy reaction with strong bases in water in a process called saponification (soap formation). 

A second way to prepare a buffer is by adding strong base to a solution of a weak acid. This produces a buffer solution if the number of moles of strong base is about half the number of moles of weak acid. As a simple example, if 1 L of 0.5 M NaOH is mixed with 1 L of 1.0 M CH3 CO2 H, hydroxide anions react quantitatively... 

Residual silanol groups in chemically bonded phases have been associated with a number of undesirable interactions with polar solutes such as excessive peak tailing, irreproducible retention times, and excessively long retention times. These problems are particularly prevalent for amines and other strong bases. A large number of test systems have been proposed to characterize the concentration of residual silanol groups on bonded phase packings, and some representative examples are... 

Thus, Andrianov et al. (26) attempted to catalyze polymerization of a number of alkyl and alkyl/aryl cyclosilazanes using catalytic amounts of KOH or other strong bases at temperatures of up to 300°C. In general, the reactions proceed with evolution of NHj, hydrocarbons and the formation of intractable, crosslinked, brittle products even at low temperatures. Contrary to what is observed with cyclotri-siloxanes, no evidence was found for the formation of linear poly-silazanes. Copolymerization of mixtures of cyclosilazanes and cyclosiloxanes gave somewhat more tractable polymers with less evolution of hydrocarbons or ammonia, however very little was done to characterize the resulting materials. 

These end groups were removed by cleaving the C-N bond with a strong base (25% NaOH) so that the CD rings may slip off the polymer chains, and the number of CDs per polyrotaxane was estimated by H NMR, optical rotation, and UV absorption to be 12. This figure indicates that nearly the entire length of the 28 mer PEG chain was covered with CDs, because, as repeatedly noted above, the stoichiometric ratio for the complexation between PEG and a-CD is 2. 

In Part II, a weak acid is titrated with the strong base from Part I and the equivalence point will be somewhat higher than 7 (8 - 9). By titrating a known amount of solid acid with the standardized NaOH, it will be possible to determine the number of moles of ff the acid furnished. From this information, one can obtain the equivalent mass (EMa) of the acid ... 

Independent evidence for backside attack in gas-phase acid-induced nucleophilic substitutions was provided by a number of studies, carried out using stationary radiolysis." Further confirmation was provided by Morton and coworkers," who investigated the stereochemistry of the proton-induced nucleophilic substitution on (5)-(- -)- and (R)-(— )-2-butanol in the gas-phase at 10 torr in their 70-eV EBF radiolysis reactor. In the presence of a strong base, i.e., tri-n-propylamine... 

When a strong acid or base dissolves in water, almost every acid or base molecule dissociates. While there are many acids and bases, most are weak. Thus, the number of strong acids and strong bases is fairly small. 

These four buffer solutions have the same initial pH but different concentrations (shown by the numbers beside or on the bars). The pH increases with the addition of a certain amount of strong base. The more concentrated the buffer solution is (that is, the higher its buffer capacity), the smaller the change in pH is. 

Siloxane bonds are opened readily with strong bases. Nucleophilic attack at the silicon atoms is involved in the reaction mechanism. Attempts at complete hydrolysis of the siloxane bonds on the surface of Aerosil by Boehm and Schneider 267) met with limited success. Partial hydrolysis was achieved with cold water over long periods, with boiling water in limited time, and by the action of ammoniacal pyrocatechol solutions. However, the number of silanol groups never exceeded 3.3OH/100A. Ashasbeenshownonpage228, avalueof ca. 5OH/100A would be expected from theoretical considerations. 

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