Ion displacement

The Williamson ether synthesis (Sec tion 16 6) An alkoxide ion displaces a halide or similar leaving group in an Sn2 reaction The alkyl halide cannot be one that is prone to elimination and so this reaction is limited to methyl and primary alkyl halides There is no limitation on the alkoxide ion that can be used... 

Substitution Titrations. Upon the introduction of a substantial or equivalent amount of the chelonate of a metal that is less stable than that of the metal being determined, a substitution occurs, and the metal ion displaced can be titrated by the chelon in the same solution. This is a direct titration with regard to its performance, but in terms of the mechanism it can be considered as a substitution titration (or replacement titration). 

In both cases n is the number of hydrogen ions displaced in the formation of the complex. In solutions where the ratio of free chelating agent to complex, ], is held constant, the slopes of the curves pM vs pH are equal. o n m. the region where H A is the principal form of the chelating... 

Halogen atoms on benzazole rings can be activated toward nucleophilic displacement by electron-withdrawing groups. Thus azide ion displaces chlorine from 5-chloro-4-nitro- and 4-chloro-7-nitro-benzofuroxan (65JCS5958). 

This class was first reported in 1924 and was formed 62HC(17)l) by cyclization of a-bromo-/3-aryl-y-nitroketones. The direct synthesis by oxygenation of 2-isoxazolines has not been reported. To date only 3-substituted derivatives have been prepared. Aryl-nitromethanes react with nitrostilbene to form isoxazoline A-oxide by a nitrile ion displacement (Scheme 138) <62HC(17)1, 68TL3375). 

Several examples of nucleophilic displacement of nitro-activated leaving groups have been recorded. 5,6-Dinitrobenzofuroxan with aniline and p-bromoandine gives the corresponding substitution product (50). Azide ion displaces chloride from both 5-chloro-4-nitro- and 4-chloro-7-nitrobenzofuroxan (51 and 52) the product from the former loses nitrogen spontaneously to give furoxanobenzo-furoxan (benzobisfuroxan, 17), which is also formed, although in poor... 

Because they re negatively charged, enolate ions act as nucleophiles and undergo many of the reactions we ve already studied. For example, enolates react with primary alkyl halides in the SK2 reaction. The nucleophilic enolate ion displaces halide ion, and a new C-C bond forms ... 

Thus we think of the chemical ionization of paraffins as involving a randomly located electrophilic attack of the reactant ion on the paraffin molecule, which is then followed by an essentially localized reaction. The reactions can involve either the C-H electrons or the C-C electrons. In the former case an H- ion is abstracted (Reactions 6 and 7, for example), and in the latter a kind of alkyl ion displacement (Reactions 8 and 9) occurs. However, the H abstraction reaction produces an ion oi m/e = MW — 1 regardless of the carbon atom from which the abstraction occurs, but the alkyl ion displacement reaction will give fragment alkyl ions of different m /e values. Thus the much larger intensity of the MW — 1 alkyl ion is explained. From the relative intensities of the MW — 1 ion (about 32%) and the sum of the intensities of the smaller fragment ions (about 68%), we must conclude that the attacking ion effects C-C bond fission about twice as often as C-H fission. 

Precipitates and complex salts 1. A more reactive ion displaces a less reactive ion in Q1 (A3) 25... 

Seven chemical reactions were identified from the chemistry syllabus. These chemical reactions were selected because they were frequently encountered during the 2-year chemistiy course and based on their importance in understanding concepts associated with three topics, namely, acids, bases and salts, metal reactivity series and inorganic chemistry qualitative analysis. The seven types of chemical reactions were combustion of reactive metals in air, chemical reactions between dilute acids and reactive metals, neutralisation reactions between strong acids and strong alkalis, neutralisation reactions between dilute acids and metal oxides, chemical reactions between dilute acids and metal carbonates, ionic precipitation reactions and metal ion displacement reactions. Although two of the chemical reactions involved oxidation and reduction, it was decided not to include the concept of redox in this study as students had only recently been introduced to ion-electron... 

Reactions of the same halogenophosphazenes with ammonia were also described, in which halide-ion displacement took place at the phosphazenyl group rather than at the thiophosphoryl group ... 

The potentials pertinent to the series correspond to a temperature of 25 °C. In many cases, ion displacement equilibria lie so far towards one side of the equation that no significant change in the position of the equilibrium arises because of the altered potential conditions at temperature other than 25 °C. 

Ion exchange is actually a far more complicated process than the simple exchange of one cation for another or one anion for another, particularly for complex polyions such as proteins and oligonucleotides. Each ion of the stationary or mobile phase is surrounded by a cluster of counterions and water. When an ion in the mobile phase is transferred to the stationary phase, the cluster of counterions and water surrounding it is partially or completely displaced. A similar event occurs at the binding site of the stationary phase. Ions displaced from the stationary phase undergo the converse process. The... 

In accordance with the known equation L2 = 2Dt, the mean ion displacement squared, L, at time t is proportional to diffusion coefficient, D. Since we could not find any reliable data on diffusion coefficients for... 

Mass spectra of OPEOs, their acidic metabolites, OPEC and halogenated derivatives in El and Cl modes have been reported [80-82]. The most prominent ions formed under Cl resulted from alkyl ion displacement and olefin displacement, and those formed under El resulted from benzylic cleavage [82]. 

Trifluoromethyl thioethers are produced in a fluoride-catalysed one-pot reaction of alkyl or aryl thiocyanates with trifluoromethyl silanes [37]. The reaction is initiated by fluoride ion displacement of the trifluoromethyl anion from the silane the thioether is formed from the thiocyanate by displacement by the trifluoromethyl anion of the cyanide ion, which then perpetuates the reaction. Trifluoromethyl selenoethers are obtained by an analogous route. In a similar manner, disulphides can be converted into trifluoromethyl thio- or selenoethers [38],... 

The U ion displacement from the aryloxide plane in addition to the increased steric bulk provided by the adamantane substituents of lead to a narrow and approximately 4.7A deep cylindrical... 

During electrophoretic separation, the analyte ions displace background co-ions equivalent to their charge. The difference in the conductivity between the analytes and the BGE co-ions induces a signal recorded by the C D detector. It is, therefore, important for optimal sensitivity that the difference in conductance between the analyte and the electrolyte be as high as possible. On the other hand, optimal efficiency of separation is attained when the /tBCE and /tanaiyte are matched. Howevei the ji and the equivalent conductance leqmv are linked ... 

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