Exchange reactions, effect

Basic Extractants. Only long-chain quaternary ammonium salts, R3NCH3 X , ia which R represents Cg—0 2 groups and X nitrate or thiocyanate, are effectively used for REE separations (see Quaternary ammonium compounds). The extractant reacts with REE according to an anion-exchange reaction ... 

It is also important to prevent the reaction of dye developers with one another. An unoxidized dye developer migrating through overlying layers of the negative could reduce and release an oxidized, immobilized dye developer, thus effecting an exchange. Reaction with quaternary salts included in the reagent aids in the immobilization of the oxidized species (66). 

Zn/EtOAc or THF, reflux, 3-12 h, 40-100% yield. It is more efficient to prepare this ketal by an exchange reaction with the dimethyl or diethyl ketal than directly from the carbonyl compound. Hydrolysis can eilso be effected by acid catalysis. 

The exchange of aromatic protons can be effected in the absence of any -OH or —NH2 activating group during the course of a Clemmensen reduction in deuteriochloric and deuterioacetic acid mixture (see section Ill-D). This reaction has been carried out with various tricyclic diterpenes and is best illustrated by the conversion of dehydroabietic acid into its 12,14-d2-labeled analog (40 -+ 41).Amalgamated zinc is reportedly necessary for the exchange reaction since the results are less satisfactory when a zinc chloride-mercuric chloride mixture is used. 

This additional effect corresponds to the exchange reaction between ammonium fluorotantalate and lithium fluoride that yields lithium heptafluorotantalate ... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

The formation of a bis(guanidinate)-supported titanium imido complex has been achieved in different ways, two of which are illustrated in Scheme 90. The product is an effective catalyst for the hydroamination of alkynes (cf. Section V.B). It also undergoes clean exchange reactions with other aromatic amines to afford new imide complexes such as [Me2NC(NPr )2]2Ti = NC6F5. ... 

For a discussion of solvent effects on organotin alkyl exchange reactions, see Petrosyan, V.S. J. Organomet. Chem., 1983, 250, 157. 

The reason for the effectiveness of triphenylphosphine is at present uncertain, although its eventual isolation as triphenylphosphine oxide indicates that it may well function as a scavenger for the thallium(III) released in the metal-metal exchange reaction. 

Electronic Effects in Metallocenes and Certain Related Systems, 10, 79 Electronic Structure of Alkali Metal Adducts of Aromatic Hydrocarbons, 2, 115 Fast Exchange Reactions of Group I, II, and III Organometallic Compounds, 8,167 Fluorocarbon Derivatives of Metals, 1, 143 Heterocyclic Organoboranes, 2, 257... 

Dodson et al. ° have also studied in detail the effect of added bromide on the exchange reaction using precipitation and extraction separations and ° T1 and ° T1 as indicators. The variation in the rate of exchange was found to be governed by the law... 

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