Potassium acetate preferential

Iodine potassium acetate Preferential replacement of halogen by acetoxy groups... 

The displacement is effected preferentially by a nucleophilic group already in the molecule. Thus, in the above reaction there is no evidence that OTs- is displaced by the external ion, OMe-, under the conditions used, nor is there ahy displacement of OTs- of a sugar sulfonate by OAc-, Buch as was found to occur when the sulfonate of a monohydric aliphatic alcohol was treated with potassium acetate.11... 

Acetic anhydride I potassium hydroxide Preferential dehydration of alcohols frans-Ethylene derivatives from alcohols... 

A detailed study of the formation of n-octyl ethers under solidrliquid two-phase conditions in the absence of an added solvent has been reported [10], Potassium alkoxides tend to produce higher yields of the ethers than do the corresponding sodium derivatives, but octene is the major product in the reaction of 1-bromooctane with potassium t-butoxide. High temperatures also tend to promote the preferential formation of octene and slightly higher yields of the ethers are obtained using n-octyl tosylate in preference to n-octyl bromide. p-Fluorinated acetals have been prepared either under basic catalytic liquidrliquid or solidrliquid conditions from the fluori-nated alcohol and dichloromethane [11] with displacement of the fluorine atoms. 

Silver ion makes possible in the second reaction an isnmeri/ation-free hydrolysis of the S,0 acetal to ketone 32. Generation of the cnol triflate 33 is accomplished in the third step with the Hendrickson-Me M it rry reagent (Tf2NPh).10 Addition of an alcohol produces the potassium aikoxide, which because of its lower basicity permits isomerization to the thermodynamically favored enolate. Chemose-lective reaction to bromohydnn 9 is achieved in the last step with NBS as brominating agent in aqueous THF. NBS acts here as a source of cationic bromine in an ionic mechanism. The intermediate bromonium ion forms preferentially at a) electron-rich double bonds and h) the sterieally least hindered double bond. It also opens in such a way as to provide the most stable carbocation. 

Pellizzari and Roncagliolo2 prepared this compound by reaction of carbohydrazide in dilute acetic acid with 2 mols of potassium cyanate and also by condensation of carbohydrazide- A-carboxamide hydrochloride with 1 mol of cyanate. The former procedure does not give a pure product, probably because of the preferential formation of the less soluble carbohydrazide-A-carboxamide. The latter reacts wjth hydrochloric acid to form the hydrochloride, which is water-soluble. Prior condensation of carbohydrazide to form the A-carboxamide is advantageous, since the hydrochloride of this compound will undergo further reaction with cyanate to give the desired product by precipitation from water. When the procedure outlined below is followed, it is not necessary to recrystallize the carbohydrazide-A, A -dicarboxamide unless an extremely pure material is desired. 

Cho et al. reported that a-alumina is formed from aluminum hydroxide prepared by precipitation with potassium hydroxide. However, when alkaline hydroxide is used as the precipitation agent, alkali cations are incorporated into the product, and commercial gibbsite samples are always contaminated with a small amount of sodium ions. Therefore their starting material seems to be contaminated with potassium, and the presence of potassium ions in their precursor seems to play an important role in the nucleation of a-alumina. They also reported that hydroxyl ions, acetic acid, and pyridine added to the glycothermal reaction system affect the morphology of the a-alumina particles because of their preferential adsorption to a specific surface. ... 

Alkylation of 2-substituted l/f-[l,2,4]triazolo[l,5-a]benzimidazoles (88) with alkyl halides and dialkyl sulfates occurs at positions 3 or 4 (but not position 1) alkylation of the neutral substrates (path A, Equation (7)) gives predominantly or exclusively 2,3-disubstituted 3/7-[l,2,4]triazolo[l,5-a]benzimidazoles (89) <89KGS209> whereas alkylation of the anion (path B, Equation (7), in the presence of potassium hydroxide or sodium acetate) leads preferentially to 2,4-disubstituted 4H-[l,2,4]triazolo[l,5-a]benzimidazoles (90) <88SC1995, 89KGS209). 

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