Molecular similarities determination

Langer, T. (1994). Molecular Similarity Determination of Heteroaromatics Using CoMFA and Multivariate Data Analysis. Quant.Struct.-Act.Rdat., 13,402-405. 

Langer, T. Molecular similarity determination of heteroaromatic ring fragments using GRID and multivariate data analysis. Quant. Struct.— Act. Relat. 1996,15, 469-474. 

As noted above, all of the colligative properties are very similar in their thermodynamics if not their experimental behavior. This similarity also extends to an application like molecular weight determination and the kind of average obtained for nonhomogeneous samples. All of these statements are also true of osmotic pressure. In the remainder of this section we describe osmotic pressure experiments in general and examine the thermodynamic origin of this behavior. 

The molecular mass determined osmometrically corresponds to the formula S5O. The SO stretching vibration was observed in the infrared spectrum at 1119 cm (at -65 °G) indicating an exocyclic sulfoxide group similar to the one in SsO (see below). At -50 °G the solution of S5O may be kept for several days without decomposition which usually results in a Tyndall effect caused by a colloidal polymeric sulfuroxide which is the expected decomposition product. At 25 °G some decomposition already occurs within... 

Two objects are similar and have similar properties to the extent that they have similar distributions of charge in real space. Thus chemical similarity should be defined and determined using the atoms of QTAIM whose properties are directly determined by their spatial charge distributions [32]. Current measures of molecular similarity are couched in terms of Carbo s molecular quantum similarity measure (MQSM) [33-35], a procedure that requires maximization of the spatial integration of the overlap of the density distributions of two molecules the similarity of which is to be determined, and where the product of the density distributions can be weighted by some operator [36]. The MQSM method has several difficulties associated with its implementation [31] ... 

The hydrogenation of 5 was carried out in an experimental manner similar to that of 2 (Scheme 8). No observation of the aromatic peak in the NMR spectra of the product indicated the occurrence of the perfect deben-zylation, giving rise to polysaccharide 7. The molecular weight determined by GPC with water eluent was 5,600, which is in good agreement with the calculated value (6,200). The solubility of 7 in water, DMSO, and DMF is higher than that of 3. 

The plastic deformation in several amine and anhydride cured epoxy resins has been studied. The experimental results have been reasonably interpreted by the Argon theory. The molecular parameters determined from the data based on the theory reflect the different molecular structures of the resins studied. However, these parameters are in similar enough range to also show the structural similarity in these DGEBA based systems. In general, the mechanisms of plastic deformation in epoxy resins below T are essentially identical to those in amorphouE thermoplastics. The yield stress level being related to the modulus that controls the intermolecular energy due to molecular deformation will, however, be affected by the crosslinks in the thermosets. 

The dimer has also been isolated from photolysis of dried uracil deposits on filter paper,33 and its elementary composition and molecular weight determined. It has an ultraviolet spectrum similar to that of thymine dimer (15). Uracil can be recovered by photolysis of the dimer in solution at 240 nm, but only to the extent of 75%. The photoreversal of dimer in solution gives, in part, the photohydrate.33 The thermal reversibility of the photolyzed aqueous solution ranges from 17 to 44% recovery of absorbance. 

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