Attraction steric

The route has also been applied to TBS-substituted propargylic mesylates (Eq. 9.39) [45]. Interestingly, the isomeric propargylic silanes are not formed despite the more attractive steric environment for a direct SN2 displacement at the primary center. 

A quantitative measure of the sum of the interactions between the two film interfaces is the disjoining pressure II. It is the excess pressure between the pressure in the film and the pressure of the corresponding liquid. This difference is due to interactions between the film interfaces which are mainly determined by electrostatic repulsion between (charged) interfaces, van der Waals attraction, steric repulsion between the adsorbed surfactant molecules, and structural forces. Disjoining pressure isotherms (disjoining pressure as a function of film thickness) have been measured in a so-called thin film pressure balance (TFPB). 

C. H. Marzabadi, J. E. Anderson, J. Gonzalez-Outeirino, P. R. J. Gaffney, C. G. H. White, D. A. Tocher, and L. J. Todaro, Why are silyl ethers conformationally different from alkyl ethers Chair-chair conformational equilibria in silyloxycyclohexanes and their dependence on the substituents on silicon. The wider roles of eclipsing, of 1,3-repulsive steric interactions, and of attractive steric interactions, J. Am. Chem. Soc., 125 (2003) 15163—15173. 

Preferred gauche conformations of 1-alkyl-2-arylethanes and 1,2-diaryl-ethanes have been interpreted in terms of attractive steric interactions between the hydrocarbon moieties (Hirola et al., 1985), and, by having opposite polarity in the aryl groups, electrostatic or charge-transfer interactions may stabilize the gauche form of 1,2-diarylethanes (El-Torki and Jacobus, 1985). 

Internal Rotation in 1,3,5-Trineopentylbenzenes. VII. Evidence for Attractive Steric Effects. R. E. Carter and P. Stilbs, /. Am. Chem. Soc., 98, 7515 (1976). Barrier to Internal Rotation in 1,3,5-Trineopentylbenzenes. 8. Molecular Mechanics Calculations. Theoretical Evidence for Attractive Steric Effects. B. Aurivillius and R. E. Carter, J. Chem. Soc., Perkin Trans. 2, 1033 (1978). Crystal and Molecular Structure of 2,4,6-Tribromo-l,3,5-trineopentyl-benzene Indication for Attractive Steric Effects in the Crystal. 

Attractive steric interactions are a feature of all molecules which can be analysed conformationally. The total enthalpy of any conformation will thus include an attraction term, which in a polyatomic molecule may be considerable. Often, of course, repulsive steric interactions will be considerably greater and will be analysed as determining the molecular conformation. It is not uncommon, however, that molecular mechanics calculations for a molecule suggest that the sum of all interactions greater than 1,4 with respect to each other is attractive, which is inherently reasonable when a little consideration is given to the interatomic distances involved. 

Such weak forces are difficult to quantify and will not be further discussed here, except to consider whether the position of a conformational equilibrium in saturated hydrocarbons is ever determined by attractive steric interactions. The best evidence... 

In molecules with little steric strain but a large number of atoms, attractive steric interactions contribute significantly to the net steric strain and offer an extreme test of whether a molecular mechanics program gives a correct balance of repulsive and attractive van der Waals forces. Molecules which may fall into this class are the medium- to large-ring cycloalkanes. 

Helical conformations have been observed in polymethylene, the epitome of a long saturated hydrocarbon. Insofar as a helical structure brings distant atoms closer together than in an extended linear conformation, attractive steric interactions offer an enthalpic contribution towards an explanation of this helicity. 

The results are from Reference 57, although there is no discussion of attractive steric interactions in this paper. 

The predominance of cij-(l) in the equilibrium depicted in Scheme 3.2 has been attributed to a dominant attractive steric interaction between the axial oxygen and the 5yn-diaxial hydrogen atoms at the 3,5 positions. According to this... 

Among dispersed magnetic particles, four different interparticle interactions exist— these are the van der Waals forces, magnetic attraction, steric repulsive forces, and electric repulsive forces. Van der Waals forces or London dispersion forces originate fi-om die interaction between orbital electrons or induced vibrating dipoles. For the equivalent two spherical particles, Hamaker s equation holds [95]. This force is strong only within short distances. 

The interactions between the particles (Coulomb repulsion, van der Waals attraction, steric, magnetic, antibody-antigen on surfaces) could be controlled via the particle production and the type of carrier fluids used. 

---