Potassium substitution, effect

Interaction of iV-pentafluorophenylcarbonimidoyl dichloride with benzonitrile and aluminium trichloride leads to l-pentafluorophenyl-4,6-diphenyl-13 -triazin-2-one along with urea derivatives . Reaction of perfluoro-5-azanon-4-ene with a range of bidentate nitrogen nucleophiles (urea, substituted amidine hydrochlorides and guanidine), in the presence of triethylamine or potassium hydroxide, effectively provides fluorinated 1,3,5-triazines 16-19 <00JFC(103)105>. 

Catalytic Combustion of Ethane over Ehgh Surface Area Lni.xKxMnOs (Ln = La, Nd) Perovskites The effect of Potassium Substitution. 

Ng Lee, Y., Sapiha, F., Martimez, E., Folgado, J.V., and Cort6s Corberfin, V. (1997) Catalytic combustion of ethane over high surface area Lni—xKxMn03 (Ln=La, Nd) perovskites the effect of potassium substitution, in 3rd World Congress on Oxidation Catalysis... 

Ura et al. [35] also reported that the partial substitution of strontium by potassium in Sri J< ,Ti03 perovskites improves the catalytic combustion of soot in N0 /02 mixtures with soot-catalysts mixtures prepared in loose contact. It was observed that potassium favors the creation of oxygen vacancies on the perov-sldte surface where molecular oxygen or NO are adsorbed forming basic surface oxygen species active for soot oxidation. In this line, it was confirmed that potassium substitution into the perovskite framework is more effective than a potassium salt impregnation [36]. 

As mentioned above, since the ROP of cyclic carbonates is an equilibrium reaction, six-membered cychc carbonates show a strong substitution effect on the equihbrium monomer concentration. The anionic ROP of l,3-dioxan-2-one (2) and 5,5-disubstituted l,3-dioxan-2-ones (10, 11, 12, 14) in THF solution using potassium tert-butoxide as initiator revealed an increasing monomer concentration at... 

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

Solvent Effects on the Rate of Substitution by the S 2 Mechanism Polar solvents are required m typical bimolecular substitutions because ionic substances such as the sodium and potassium salts cited earlier m Table 8 1 are not sufficiently soluble m nonpolar solvents to give a high enough concentration of the nucleophile to allow the reaction to occur at a rapid rate Other than the requirement that the solvent be polar enough to dis solve ionic compounds however the effect of solvent polarity on the rate of 8 2 reactions IS small What is most important is whether or not the polar solvent is protic or aprotic Water (HOH) alcohols (ROH) and carboxylic acids (RCO2H) are classified as polar protic solvents they all have OH groups that allow them to form hydrogen bonds... 

Because of the special stabiHty of the hexafluoroarsenate ion, there are a number of appHcations of hexafluoroarsenates. For example, onium hexafluoroarsenates (33) have been described as photoinitiators in the hardening of epoxy resins (qv). Lithium hexafluoroarsenate [29935-35-1] has been used as an electrolyte in lithium batteries (qv). Hexafluoroarsenates, especially alkaH and alkaline-earth metal salts or substituted ammonium salts, have been reported (34) to be effective as herbicides (qv). Potassium hexafluoroarsenate [17029-22-0] has been reported (35) to be particularly effective against prickly pear. However, environmental and regulatory concerns have severely limited these appHcations. 

Sodium is an indispensable element for some crops (notably sugar beet), can partially substitute for potassium in several crops, contributes to neutralising soil and subsoil acidity, and has a positive effect on soil phosphoms solubiUty. Sodium is an essential nutrient for cattle, and sodium appHcation to soil increases its content in pastures. Sodium nitrate is particularly effective as a nitrogen source for sugar beet, vegetable crops, tobacco, and cotton (qv), and for any crop in acid soils. 

There is probably no better evidence for a template effect than its application directly in the solution of a synthetic problem. Rastetter and PhiUion have utilized a substituted 19-crown-6 compound (shown below in Eq. 2.9) in the formation of macrocyclic lactones. Although there were certain experimental variations and the the possibility of intermolecular potassium ion complexation, the overall formation of lactone was favorable. 

Those reactions of halogenopyridines with potassium amide and lithium piperidide which proceed via 3,4-pyridyne form the 3- and 4-substituted pyridine derivatives in ratios of 1 2 and 1 1, respectively (see Section II, A, 1). It appears that the ring nitrogen atom has an orienting effect on these additions, but the quantitative divergence of the addition of ammonia and piperidine is not understood at present. 

For many years such media have been based on strong salt solutions, e.g. calcium chloride brines. Sodium dichromate has been used (seep. 17 26), but recently other inhibitors have been claimed to be effective. One patent quotes N-alkyl-substituted alkanolamines, e.g. 2-ethyl ethanolamine -I- BTA at pH A mixture of hydrazine hydrochloride -i- BTA has been claimed as well as a mixture of gelatin -h triethanolamine -h potassium dihydrogen phosphate . Other examples are to be found in the patent literature and the above are quoted to illustrate the diversity of chemicals that may be used. 

The kinetics of decarboxylation of 4-aminosalicylic acid in some buffer solutions at 50 °C were studied. The first-order rate coefficients increased with increasing buffer concentration, though the pH and ionic strength were held constant (Table 217). This was not a salt effect since the rate change produced by substituting potassium chloride for the buffer salt was shown to be much smaller. It follows from the change in the first-order rate coefficients (kx) with... 

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