Method of substitution

Replacement of Hydrogen. Three methods of substitution of a hydrogen atom by fluorine are (/) reaction of a G—H bond with elemental fluorine (direct fluorination, (2) reaction of a G—H bond with a high valence state metal fluoride like Agp2 or GoF, and (J) electrochemical fluorination in which the reaction occurs at the anode of a cell containing a source of fluoride, usually HF. 

Rosensweig, R.E. Method of substituting one ferrofluid solvent for another. US Patent (1970) 3,917,538. 

Chemical Substitution Phthalates are used to provide flexibility to the polymer backing. The use of alternative plasticizers represents the most direct method of substitution. In some cases this choice may have little impact on production techniques, and so be the most economically favourable option in immediate terms. 

Anions obtained formally by loss of a hydron from a parent hydride (see Table 5.2 p. 99 for a list of parent hydride names) are conveniently named by the methods of substitutive nomenclature. 

Carbon is, of course, unique in the number of hydrides it forms, but the elements in the proximity of carbon in the Periodic Table have a similar, if more restricted, propensity to form hydrides. Silicon, germanium, boron and phosphorus are obvious examples. For hydrides of these elements, and especially for their organic derivatives, the methods of substitutive nomenclature can be applied to obtain suitable names. 

An area of current development is the nomenclature of organometallic compounds. Organometallic compounds of Main Group elements can, to a first approximation, be considered to be derivatives of hydrides, and the methods of substitutive nomenclature can be applied. Even then, the accessibility of different oxidation states, as with phosphorus(iii) and phosphorus(v), introduces complications. Transition metal organometallic compounds are even more difficult to treat, and the development of a unified, self-consistent and accepted and applied nomenclature is not easy. Witness the different ways (k, t and italicised symbols) for denoting donor atoms in ligands. 

S. Murahashi, Kagaku (Kyoto) 40, 269-271 (1985) New Synthetic Method of -Substituted Amines". 

This same expression can be derived for single-pan balances that use the method of substitution of weights. The fact that the lever arms are unequal and that there is a constant load on the balance does not alter the final expression. 

The location of the metal cation (or cations) in alcoholates has been investigated by the method of substitutive methylation for the sodium derivatives of methyl a-D-glucopyranoside, amylose, and cellulose. The method assumes that methylation by either dimethyl sulfate or methyl iodide occurs only at an anionic oxygen atom. Lenziu methylated the mono-sodium alcoholates (prepared in boiling, butanolic sodium hydroxide by the... 

To solve the differential equation 2.38 subject to the boundary conditions 2.39 and 2.41 we adopt the standard method of substituting the trial solution C — Aemi and obtain the auxiliary equation ... 

In the second case, if the species mobilities differ greatly, the dimensionality of the system of kinetic equations decreases [103], Let all the components be divided into two groups of species a slow (5) and a rapid (r) one. This yields three types of pair functions. For the rapid species the condition of the equilibrium distribution can be considered as satisfied. Then, for the pair functions of types sr and rr instead of the kinetic Eqs. (32) algebraic relations in Appendix A apply, whose dimensionality can be lowered using the method of substitution variables according to Appendix B. In this case the kinetic Eqs (31) for the local concentrations and Eq. (32) for the pair functions type ss do not change. A similar situation remains in passing to the one-dimensional discrete and point-like models. 

By reaction of a 1,1-difluoroethene with tributylphosphane in the presence of boron trifluoride-diethyl ether complex, the vinylphosphonium salt is obtained. On subsequent hydrolysis the selectivity of formation of the Z- and F-isomer is 100%, but it diminishes after the introduction into the alkene. together with the perfluoroalkyl group, of substituents such as phenyl and 4-methoxyphcnyl. In accordance with this methodology, a method of substitution of fluorine by hydrogen at the fluoroolefinic double bond has been developed.194,206 The first stage of this reaction includes the formation of a fluoro-/5-phosphane from the fluoroalkene and tributylphosphane. The decomposition of this /l5-phosphane in the aqueous solvent leads to a fluoroalkene, e.g. formation of l.206... 

Ylides add to heteroallenes (see equations 78 and 79). In the case of silyl-substimted ylides the initially formed betaine stabilizes by silyl group migration instead of proton migration. a-Trimethylsilylalkylidenephosphoranes can be transformed into a-trimethylsilylphosphonium salts which can be desilylated by fluoride ions, thus providing a method of substituting trimethylsilyl by alkyl or iodine (equation 88, see also equation 18)... 

A new and general method of substitution at aromatic carbon has been uncovered. Reactions involve electron transfer steps and the formation of radical anion and radical intermediates. Many of the transformations are unprecedented in aromatic chemistry they represent major, new sequences which will have considerable value in syntheses. The radical anion method of substitution at aromatic carbon was first reported by Kim and Bunnett in 1970.96,97) The method is related to radical-anion substitution at aliphatic carbon.98, ")... 

Elass, A., Brocard, J., Surpateanu, G. and Vergoten, G. (1999) Conformational searching using the comparative molecular field analysis (CoMFA) method of substituted arene-tricarbonyl-chromium complexes./. Mol. Struct. (Theochem), 466, 21-33. 

The method of substitution is not limited to two equations and is not limited to linear equations. In the following example, we treat a nonlinear system of two equations ... 

Solve the simultaneous equations by hand, using the method of substitution ... 

If we have a constrained maximum or minimum problem with more than two variables, the direct method of substituting the constraint relation into the function is usually not practical. Lagrange s method finds a constrained maximum or minimum without substituting the constraint relation into the function. If the constraint is written in the form g(x, y) = 0, the method for finding the constrained maximum or minimum in f x, y) is as follows ... 

In Chapter 3, we discussed the use of the method of substitution and the method of elimination to solve the linear inhomogeneous set of two simultaneous equations ... 

To solve for numerical values of two variables, two equations are required, and they must be solved simultaneously, and similarly for more variables. We presented several methods for solving simultaneous equations. First was the method of substitution, which is not limited to linear equations, but which is not practical for more than two or three equations. We then presented several methods which can apply to sets of linear inhomogeneous equations. Cramer s method is a method... 

II. To solve the normal equations. We can determine the values of x, y, z, from this set of simultaneous equations (2) by any method we please, determinants ( 179), cross-multiplication, indeterminate multipliers, or by the method of substitution.1 The last method is adopted here. Solve the first normal equation for x, thus... 

We can try the old method of substitution to solve this problem. We know that the integral of over X gives a simple logarithmic form. Therefore, we can try using the substitution of u = Vy ... 

Reaction of o-iodoaniline (33) with internal alkynes offers a good synthetic method of substituted indoles [13], A practical synthesis of psilocin was carried out by utilizing the reaction of the iodoaniline derivative 34 with internal alkyne to form an indole derivative as a key reaction [14], The thieno[3.2- ]pyrrole 37 was obtained by the reaction of 2-iodo-3-aminothiophene (35) with the alkyne 36 [15], These reactions of aryl iodides proceed in the absence of phosphine ligands. The isocoumarin 39 was obtained by the reaction of methyl o-iodobenzoate (38). Poor yield was obtained when the free acid was used [11]. 

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