Effect on molecular shape

Ethene, H2C = CH2, serves as the starting material for the synthesis of polyethylene, from which plastic bags and milk jugs are made. Ethyne, H—C=C—H, is used as a fuel for welding torches. The double bond in ethene and the triple bond in ethyne have the same effect on molecular shape as single bonds. Predict the shapes and bond angles of ethene and ethyne. 

What property of the electron causes electron domains to have an effect on molecular shapes ... 

In which of these molecules or ions does the presence of nonbonding electron pairs produce an effect on molecular shape, assuming they are all in the gaseous state (a) S1H4, (b) PF3, (c) HBr, (d) HCN, (e) SO2. 

In which of these molecules or ions does the presence of nonbonding electron pairs produce an effect on molecular shape ... 

Another example of the shape similarity effect on molecular recognition involves the similarity between the structures of the binding sites. Investigation was made for four reaction systems I-IV each consisting of a 1 1 mixture of thiols HS—X and HS—Y... 

Table 17-11. the effect cf molecular shape on melting point d -... 

Using the formalism of statistical mechanics, Giddings et al. [135] investigated the effects of molecular shape and pore shape on the equilibrium distribution of solutes in pores. The equilibrium partition coefficient is defined as the ratio of the partition function in the pore... 

Gritsenko, O. V., Baerends, E. J., 1997, Electron Correlation Effects on the Shape of the Kohn-Sham Molecular Orbitals , Theor. Chem. Acc., 96, 44. 

M.R. Robinson, S. Wang, A.J. Heeger, and G.C. Bazan, A tetrahedral oligo(phenylene vinylene) molecule of intermediate dimensions effect of molecular shape on the morphology and electroluminescence of organic glasses, Adv. Funct. Mater., 11 413 419, 2001. 

Table 4.3 Effect of Molecular Shape on Molecular Polarity... 

Takafuji, M., Fukui, M., Ansarian, H.R., Derakhshan, M., Shundo, A., and Ihara, H., Conformational effect of silica-supported poly(octadecyl acrylate) on molecular-shape selectivity of polycyclic aromatic hydrocarbons in RP-HPLC, Anal. Sci., 20, 1681, 2004. 

The spherically shaped cryptophanes are of much interest in particular for their ability to bind derivatives of methane, achieving for instance chiral discrimination of CHFClBr they allow the study of recognition between neutral receptors and substrates, namely the effect of molecular shape and volume complementarity on selectivity [4.39]. The efficient protection of included molecules by the carcerands [4.40] makes possible the generation of highly reactive species such as cyclobutadiene [4.41a] or orthoquinones [4.41b] inside the cavity. Numerous container molecules [A.38] capable of including a variety of guests have been described. A few representative examples of these various types of compounds are shown in structures 59 (cyclophane) 60 (cubic azacyclophane [4.34]), 61a, 61b ([4]- and [6]-calixa-renes), 62 (cavitand), 63 (cryptophane), 64 (carcerand). 

The medium may have a marked effect on the shape of receptor molecules itself. Shape modifications could strongly influence their substrate binding properties, for instance in the case of amphiphilic cyclophane receptors subjected to hydrophobic-hydrophilic factors in aqueous solution. Such medium effects in action are visualized by the solid state structures of two different forms of the water-soluble hexasodium salt of the macrobicyclic cyclophane 66, which could be crystallized in two very different shapes an inflated cage structure 71 building up cylinders disposed in a hexagonal array and a flattened structure 72 stacked in molecular layers separated by aqueous layers in a lamellar arrangement [4.73]. These two... 

It should also be noted that the stability of the distinct mesophases can be quite different. It seems that there is a significant effect of molecular shape and topology, stabilizing SmA phases in the system 41/43 and Colhex phases in the system 35/37. In addition, the mesophase stability is often reduced close to the transition to another mesophase (see Fig. 15). Hence, the order-disorder temperatures can only be roughly estimated based on segmental solubility parameters [24, 25]. 

Y. Queneau, J. Gagnaire, J. J. West, G. Mackenzie, and J. W. Goodby, The effect of molecular shape on the liquid crystal properties of the mono-0-(2-hydroxydodecyl)sucroses, J. Mater. Chem., 11 (2001) 2839-2844. 

The etched liquid crystal modified capillaries were also tested for the separation of protein mixtures [32], For the two liquid crystal moieties investigated, similar separations of the protein mixtures were obtained. This result is not surprising since previous studies in HPLC have shown that liquid crystals are effective in discriminating between small molecules based on molecular shape [64-66]. The close association of the... 

Molecules in the transition area of molecular weight (2000-4000 Da depending on molecular shape, rigidity, and solvent viscosity) show little or no NOE. For these molecules an alternative experiment called ROES Y (rotating-frame Overhauser effect spectroscopy, Chapters 8 and 10) is effective. 

Figure 6. Effect of molecular shape on local concentration at 400 K. Sorption of n-...

Krukowski et al. [24] studied the effect of molecular shape in details by performing exact enumerations on lattice models of different molecular shapes. They calculated the entropic component of the chemical potential, i.e.,... 

Braga, D. and Grepioni, F. (1991). Effect of molecular shape on crystal building and dynamic behavior in the solid state from crystalline arenes to crystalline metal arene complexes. Organometallics, 10, 2563-9. [85]... 

The density functional method as applied by Tarazona to deal with classical fluids has been used to calculate the orientation of triatomic molecular fluids near the solid-liquid interface. The results give valuable suggestions about the effect of molecular shape on the orientation of real molecules such as liquid crystals near the solid-fluid interface. 

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