Potassium hydroxide complex

Potassium hydroxide complex with dicyclohexyl-18-crown-... 

The earliest example of the increased reactivity of the potassium hydroxide complex of dicyclohexyl- 18-crown-6 ((20] + [21]) was presented by Pedersen (1967b), who found that the sterically hindered esters of 2,4,6-trimethyl-benzoic acid [136], which are inert towards KOH in protic solvents, are readily... 

Saponification of esters of 2,4,6-trimethylbenzoic acid with potassium hydroxide complex of dicyclohexyl-1 S-crown-fi0,4... 

Potassium amide, 52, 75 Potassium azide, 50,10 Potassium f-butoxide, 52,53 Potassium hydroxide complex with dicyclohexyl-18-crown-6 polyether, 52,77... 

The physical properties of many macrocyclic polyethers and their salt complexes have been already described. - Dibenzo-18-crown-6 polyether is useful for the preparation of sharpmelting salt complexes. Dicyclohexyl-18-crown-6 polyether has the convenient property of solubilizing sodium and potassium salts in aprotic solvents, as exemplified by the formation of a toluene solution of the potassium hydroxide complex (Note 13). Crystals of potassium permanganate, potassium Lbutoxide, and potassium palladium(II) tetrachloride (PdClj + KCl) can be made to dissolve in liquid aromatic hydrocarbons merely by adding dicyclohexyl-18-crown-6 polyether. The solubilizing power of the saturated macrocyclic polyethers permits ionic reactions to occur in aprotic media. It is expected that this [)ropcrty will find practical use in catalysis, enhancement of... 

While potassium hydroxide is beneficial in catalysts containing palladium loads near 5% with low palladium loads it appears that potassium hydroxide is not always necessary. The semihydrogenation of dehydrolinalool (19) gives 100% of linalool (20) over 0.5% PCI/AI2O3 in alcoholic solvents as shown in Eqn. 16.25. Perhaps with lower palladium-loaded catalysts reactant diffusion is not a factor in the reaction, so the presumed enhanced adsorption of the potassium hydroxide complex is not as important. 

A combination of stereochemical structural refinement and. T-ray diffraction analysis has been used to determine the crystal stracture of potassium hydroxide-complexed amylose, obtained by heterogeneous deacetylation of amylose acetate. The complex crystallizes as an orthorhombic unit cell with p2,2,2 symmetry and dimensions a = 8.84,6 = 12.31, and c = 22.41 A. The conformation of the amylose chain is a distorted left-hand helix with six o-glucose residues per turn. Each three-residue asymmetric unit is complexed with one molecule of potassium hydroxide and three molecules of water. Extension of the amylose chain probably arises because of the co-ordination of the K ion. 

The main problem of using potassium hydroxide for saponification is its insolubility in organic solvents like toluene, but this can be solved by using hydrophobic and hydrocarbon soluble macrocyclic derivatives like dicyclohexyl 18-crown-6, it has been shown that potassium hydroxide is soluble in toluene. This special observation has been used for the hydrolysis of sterically hindered esters using potassium hydroxide complex in toluene (Scheme 29). 

Trivalent complexes of biguanide and periodate are also prepared commercially for water sanitation. The trivalent silver periodate, for example, is prepared by the action of potassium periodate and potassium hydroxide on Ag O ... 

Superimposed on this simple equiUbrium are complex reactions involving the oxides and hydrides of the respective metals. At about 400°C, the metal phase resulting from the reaction of sodium and potassium hydroxide contains an unidentified reaction product that precipitates at about 300°C (15). 

Other Reactions. Poly(vinyl alcohol) forms complexes with copper in neutral or slighdy basic solutions (165). Sodium hydroxide or potassium hydroxide forms an intermolecular complex with PVA (166,167), causing gelation of the aqueous solution. 

Cadmium Hydroxide. Cd(OH)2 [21041-95-2] is best prepared by addition of cadmium nitrate solution to a boiling solution of sodium or potassium hydroxide. The crystals adopt the layered stmcture of Cdl2 there is contact between hydroxide ions of adjacent layers. Cd(OH)2 can be dehydrated to the oxide by gende heating to 200°C it absorbs CO2 from the air forming the basic carbonate. It is soluble ia dilute acids and solutions of ammonium ions, ferric chloride, alkah haUdes, cyanides, and thiocyanates forming complex ions. 

The crown ethers and cryptates are able to complex the alkaU metals very strongly (38). AppHcations of these agents depend on the appreciable solubihty of the chelates in a wide range of solvents and the increase in activity of the co-anion in nonaqueous systems. For example, potassium hydroxide or permanganate can be solubiHzed in benzene [71 -43-2] hy dicyclohexano-[18]-crown-6 [16069-36-6]. In nonpolar solvents the anions are neither extensively solvated nor strongly paired with the complexed cation, and they behave as naked or bare anions with enhanced activity. Small amounts of the macrocycHc compounds can serve as phase-transfer agents, and they may be more effective than tetrabutylammonium ion for the purpose. The cost of these macrocycHc agents limits industrial use. 

Chemical Treatment. The most iavolved regeneration technique is chemical treatment (20) which often follows thermal or physical treatment, after the char and particulate matter has been removed. Acid solution soaks, glacial acetic acid, and oxalic acid are often used. The bed is then tinsed with water, lanced with air, and dried ia air. More iavolved is use of an alkaline solution such as potassium hydroxide, or the combination of acid washes and alkaline washes. The most complex treatment is a combination of water, alkaline, and acid washes followed by air lancing and dryiag. The catalyst should not be appreciably degraded by the particular chemical treatment used. 

JA5190, 940M5132). Proton abstraction from 109 gives a neutral ti C) 2-thienyl complex, 110. Such a reaction becomes impossible in case of the 2,5-dimethylthiophene analog of 109. However, use of a strong base such as potassium hydroxide in methanol gives 111. An attempted transformation of 109 to 110 by protonation with triflic acid leads, however, to the thienylcarbene complex cation 112 where the aromaticity is disrupted. 

Reaction of [Ir( -Cp )Cl2(/A-Cl)2]2 and pyrazole in the presence of potassium hydroxide leads to complex 105 characterized by the dynamic hydrogen bond between three pyrazole nuclei (86AGE1114). 3,5-Dimethylpyrazole in identical conditicHis produces 106 where two pyrazole nuclei share a proton and one is unprotonated. Addition of tetrafluoroboric acid to 106 yields 107, where the second proton is bonded to the nonchelated ligand. Addition of the third proton causes formation of [Ir( -Cp )(Hpz )3](BF4)2. 

The acetone complex [IrH2(Me2CO)(Hpz)(PPh3)2]BF4 reacts with potassium hydroxide to give 128 [94JOM(466)249 94JOM(467) 151]. The pyrazolate bridge... 

Reaction of [Rh(rj -Cp )2(/r-0H)3]2C104 with excess pyrazole or 4-bromopyr-azole and potassium hydroxide forms the neutral complexes 163 (R = H, Br)... 

ICA 97)19]. Compound 163 (R = Br) and perchloric acid yield 164, where the monodentate pyrazolate ligand is protonated. Potassium hydroxide regenerates 163 (R = Br). Dicationic complexes of the type 164 can alternatively be produced from [Rh2(r/ -Cp )2(/x-0H)3]Cl04 and perchloric acid in the presence of excess pyrazole, 4-bromopyrazole, 3-methylpyrazole, or 3,5-dimethylpyrazole. 

Biimidazole and bibenzimidazole with [(ri -2-RC3H )Pd(p-Cl)]2 (R = H, Me) taken in the 2 1 molar ratio in the presence of methanolic potassium hydroxide give complexes of the type 146 (83JCS(D)1729) and with [(ti -2-RC3H ) Pd(Mc2C0) ](C10 ) - 147. When the ratio of 2,2 -biimidazole or 2,2 -bibenz-imidazole and [(Ti -2-RC3H )Pd(p-Cl)]2 (R = H, Me) is 1 1, the homo-tetranuclear species 148 result. Heterotetranuclear palladium(II)-rhodium(I) complexes 149 (L2 = cod) follow from [(TiLcod)Rh(Hbim)] and [(ri -2-R-C3H )Pd(acac)]. They are readily carbonylated with complete substitution of... 

Triazole (HL) with Me SAuCl, the gold(I) species, in the presence of potassium hydroxide gives the polymeric complexes [AuL] with exobidentate coordination mode of the azolate ligand (79IC658). 

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