Equivalent of salt

An acid- and base-sensitive siloxycarboxylic acid was treated with AW -carbonyldi-imidazole and the resulting imidazolide (51) transformed into the desired ylide using one equivalent of salt-free methylenetriphenylphosphorane in benzene, rather than two equivalents as usually recommended. Coupling, under neutral conditions, with two equivalents of aldehyde (52) gave a mixture of diastereomeric epoxythiolates (Scheme 15).68... 

The atom economy of the cross-coupling reaction and the Heck reaction for making styrene from bromobenzene and vinyl bromide (cross), and bromobenzene and ethene (Heck) respectively are in favour of the Heck reaction, as that produces only one equivalent of salt. 

Following these considerations, the pH of these systems was actively controlled by the addition of inorganic salts (acids or bases) [51]. As a matter of fact, a 20-fold increase in the initial rate could be observed upon addition of KHC03 or K2C03 in the synthesis of Z-L-Asp-L-Phe-OMe, but 1.5 equivalents of salt were optimal to obtain yields of more than 90%. The profile of initial rate as a function of K2C03 concentration displayed a bell-shaped figure typically seen for pH effects on enzyme activity (Figure 12.3). 

These are very important quantities as they determine the current efficiency of electro dialysis, i.e. the number of gram equivalents of salt removed during passage of one Faraday of charge. 

A fermentative or biocatalytic procedure for 2KLG calls for a completely different approach to the DSP of the latter and possibly also for the conversion of 2KLG into ASA. The basic problem is that 2KLG is dissolved in the culture supernatant as a salt, due to the necessity to titrate the culture with base to maintain neutrality. The conversion of 2KLG into ASA, in contrast, requires the free acid. Traditional solutions, such as spray-drying and acidification with sulfuric acid [170] and evaporative crystallization [171], are energy intensive and coproduce an equivalent of salt, which is, parenthetically, one of the objections against the Reichstein process. 

Mathias showed that the specific heat c of a solution containing 1 g. equivalent of salt in g. equivalents of water (k at least 25) can be represented by the formula ... 

In the case of cells with transport we have already seen that the actual amount of salt transferred when one faraday passes is less than one gram-equivalent In the case of such a cell, having electrodes reversible with respect to the cation, the fraction of salt transferred is measured by the amount of amon which passes from the strong to the weak solution The amount of salt transferred per faraday is, m feet, vj u + v) of one equivalent, where /(w + 0) is the transport number of the anion In the case of a similar cell with electrodes reversible with respect to the anion, the corresponding fraction is uj(u + 0) Hence to obtain the transfer of one gram-equivalent of salt it is necessary to allow (u + v)jv faradays in the first case, or (u + v)ju faradays m the second case to flow through the cell... 

Faraday s Law as related to electrodialysis (ED) states that the passage of 96,500 amperes of electrical current for one second will transfer one gram equivalent of salt. This is equal to 26.8 amperes of current passing for 1 hour. 

Base is almost always required for Pd-catalyzed coupling reactions in order to trap out the H-X released in the final reductive elimination step or to abstract a proton from a cationic Pd-hydride (both shown in Figure 16). This generates one equivalent of salt per equivalent of product, which is not a problem for laboratory scale reactions, but certainly does limit the applicability of these coupling reactions for larger scale industrial processes. 

Write reaction equations that illustrate various ways to prepare salts, and do calculations using the concept of an equivalent of salt. (Section 9.8) Demonstrate an understanding of the words weak and strong as applied to acids and bases. (Section 9.9) Demonstrate an understanding of the titration technique used to analyze acids and bases. (Section 9.10)... 

Write reaction equations that illustrate various ways to prepare salts, and do calculations using the concept of an equivalent of salt. 

A unit that expresses the amount of ionic electrical charge for salts is the equivalent. One equivalent of salt is the amount that will produce 1 mol of positive (or negative) charges when dissolved and dissociated. To determine the amount of salt that represents 1 equivalent (eq), you must know what ions are produced when the salt dissociates. For example, potassium chloride (KCl), an electrolyte often administered to patients following surgery, dissociates as follows KCl(aq) K (aq) + Cr(aq). Thus, 1 mol, or 74.6 g, of sohd KCl provides 1 mol of positive charges (1 mol of ions) when it dissolves and dissociates. Thus, 1 eq of KCl is equal to 1 mol, or 74.6 g, of KCl. 

Endpoint of a titration (9.10) Equivalence point of a titration (9.10) Equivalent of salt (9.8)... 

The amount of potassium acetate which dissolves either in benzene or acetonitrile in the presence of 18-crown-6 is slightly lower than the amount of crown present. At concentrations of 0.55 and 1.0 molar crown in benzene, for example, potassium acetate is soluble to the extent of 0.4 and 0.8 molar, respectively. Similarly, in acetonitrile, 0.14M crown dissolves 0.1 equivalent of salt [19]. In the ester displacement reaction, the crown-potassium acetate ion pair must be more soluble than the crown-potassium bromide ion pair or one would expect catalyst poisoning. 

In general, a smaU fraction of the current is not utilized in salt transport (it is lost, for example, in the brine connection channels at the end of the membranes) the fraction r ip (pretty close to 1) utilized is called the current utilization factor. Introduce this factor in equation (8.1.403) and equate it to the gram-equivalents of salt transferred per unit time over 1 cm area at location z (Figure 8.1.47(d)) ... 

Estimation of Current in EDI The applied dc current, not the voltage, is the main parameter for the design of EDI units. The amount of current used by an EDI module is a function of the flow rate and the amount of salt being removed. Faraday s law states that 96,485 A of electric current is required for one second to move one mole of ionic charge between electrodes. This is same as 26.8 A for one hour. One can also write that one Faraday of charge is required to transfer one-gram equivalent of salt. 

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