Solvents 0-point

Instead of using point charges one may also approximate the mteraction Hamiltonian in temis of solute electrons and nuclei interacting with solvent point dipoles... 

A C NMR study in hydrocarbon solvents points to a large charge delocalization and sp character at the a-carbon of compounds 84 and 85, containing benzyl moieties, while the allylic compounds 86 and 87 have an intermediate state of hybridization at the a-carbons . 

As the solvent/feed ratio is increased, the mix point M approaches the solvent point S, and poles P and Q likewise do so. At total reflux all of the points P, Q, S, SE, and M coincide this is shown in Figure 14.7(b). 

Contrary to earlier suggestions of an SnI pathway for solvolyses of A,A-dimethyl-sulfamoyl chloride (41), the results of an extended Grunwald-Winstein equation treatment of the specific rates of solvolysis of (41) in 32 solvents pointed to an Sn2 pathway. Results of a similar treatment of its rates of solvolysis in a range of solvents supported an SN2 pathway for 2-propanesulfonyl chloride (42).59... 

The incorporation of these three solvents into a statistical design is shown in Figure 9.30. The ten mixtures shown include the three solvents (points 1,2, and 3 at the apices), 50/50 mixtures of pairs of solvents (points 4, 5 and 6), a 33/33/33 mixture of all three (point 7), and 16/16/67 mixtures of all three (points 8, 9, and 10). The data for the first seven runs in this study is shown in Figure 9.31, where it can be seen that some unexpected variations occur but there are no crossovers in peak elution order. 

The above observations on the swelling properties of the resin supports in different solvents point to the fact that the extent of swelling and solvation is a very decisive factor for the successful execution of the solid phase synthesis of longer peptides 153). 

Fig. 3-5. Geometrical representation of FA. The three-dimensional property space is defined by three solvent descriptors [e.g. tbp, fJ-, and r) and filled with 30 solvent points, some of them already lying in the plane defined by the two factors F and Fi (according to [139] and [142]).

The coordinates of each solvent point are (i) the factor (or principal component) scores F, and (ii) the factor (or principal component) loadings L. They give the information necessary to reconstitute the original physical properties D of any solvent according to Eq. (3-15). 

Two limitations are involved in the derivation of the above equation (1) the compositions of mixed solvents (points c and d) should be close enough to each other for the trapezoidal mle used to integrate the Gibbs-Duhem equation to be valid, (2) the solubility of the solid should be low enough for the activity coefficients of the solvent and cosolvent to be taken equal to those in a solute-free binary solvent mixture. In addition, the fugacity of the solid phase in Eq. (4) should remain the same for all mixed solvent compositions considered. 

It is possible to adopt a simplex strategy to explore the neighbourhood of a promising solvent. The score values are not continuous and it is therefore not possible to make reflections of the worst vertex in a strict geometrical sense. It is, however, possible to make a simplex search in an approximate way. In the exploration of the solvent space, there are two principal properties to consider. The simplex is therefore a triangle and will be defined by three solvent points in the score plot. Let one vertex correspond to the promising candidate, or to a hitherto known "useful" solvent. The other vertices are chosen not too far from the first one. Run the reaction in the three solvents selected and determine in which experiment the oucome is least favourable. Discard this point and run a new experiment in a... 

Listed in Table 6 the data on anodic oxidation of solvated electrons in different solvents point towards the different natures of non-paramagnetic associates, on the one hand, in liquid ammonia and, on the other hand, in hexamethylphosphotriamide and methylamine. In liquid ammonia, even the fast sweep (dynamic) voltammogram does not detect the second kind of particles at that bulk concentration of solvated electrons when non-paramagnetic associates exist jjjyg, the electrons that... 

It was finally found that simply changing the solvent to toluene produces bicyclic (85) in ca. 65% yield as a 70 30 mixture of p- to a-methyl isomers. This isomer ratio well reflects the isomer ratio of the diene, but the diene unfortunately isomerizes under the reaction conditions. The stereospecificity of the formation of (85) as well as the success in an apolar solvent points to a more or less concerted cycloaddition pathway. ... 

Extending these studies to ion-dipole mixtures in which a background dielectric constant is replaced by fluctuating solvent point dipoles, leads to practical nonergodic-ity due to the formation of clusters and/or strings of particles [164]. 

A point on an edge of the tetrahedron represents a binary system, a point within it a quaternary. On the faces ABS, BCS and ACS the solubility curves meet at points L, M and A, respectively, which represent the solvent saturated with two solutes. They are the starting points for the three curves LO, MO and NO, which denote solutions of three solutes in the solvent point O represents the solution which, at the given temperature, is saturated with respect to all three solutes. All these curves form three curved surfaces within the space model. The section between these surfaces and the apex of the tetrahedron indicates unsaturated solution, that between the surfaces and the triangular base complex mixtures of liquid and solid. 

The X parameter can be used as a measure of the solvent power it has a value <0.5 when the polymer is in a good solvent, and a value > 0.5 when the polymer is in a poor solvent. The point where x = 0.5 is referred to as the -solvent point. 

Hansen defined solvent as a point in three-dimensional space and solutes as volumes (or spheres of solubility). If a solvent point is wifliin the boundaries of a solute volume spaee then the solute ean be dissolved by the solvent. If tire point eharacterizing the solvent is outside the volume spaee of a solute (or resin) sueh a solvent does not dissolve the solute. The solubility model based on this eoneept is broadly applied today by modem eomputer teehniques using data obtained for solvents (the three components of solubility parameters) and solutes (eharaeteristie volumes). A triangular graph ean be used to outline the limits of... 

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