Linear arrangement

The effect of the Axilrod-Teller term (also known as the triple-dipole correction) is to make the interaction energy more negative when three molecules are linear but to weaken it when the molecules form an equilateral triangle. This is because the linear arrangement enhances the correlations of the motions of the electrons, whereas the equilateral arrangement reduces it. 

Multiple bonds are treated as a single unit m the VSEPR model Formaldehyde is a trigonal planar molecule m which the electrons of the double bond and those of the two single bonds are maximally separated A linear arrangement of atoms m carbon diox ide allows the electrons m one double bond to be as far away as possible from the elec Irons m the other double bond... 

Section 1 10 The shapes of molecules can often be predicted on the basis of valence shell electron pair repulsions A tetrahedral arrangement gives the max imum separation of four electron pairs (left) a trigonal planar arrange ment is best for three electron pairs (center) and a linear arrangement for two electron pairs (right)... 

Valence shell electron pair repulsion (VSEPR) model (Section 110) Method for predicting the shape of a molecule based on the notion that electron pairs surrounding a central atom repel one another Four electron pairs will arrange them selves in a tetrahedral geometry three will assume a trigo nal planar geometry and two electron pairs will adopt a linear arrangement... 

The above discussion points out the difficulty associated with using the linear dimensions of a molecule as a measure of its size It is not the molecule alone that determines its dimensions, but also the shape in which it exists. Linear arrangements of the sort described above exist in polymer crystals, at least for some distance, although not over the full length of the chain. We shall take up the structure of polymer crystals in Chap. 4. In the solution and bulk states, many polymers exist in the coiled form we have also described. Still other structures are important, notably the helix, which we shall discuss in Sec. 1.11. The overall shape assumed by a polymer molecule is greatly affected... 

As an explanation of the preferred formation of pyrrolidines as compared to lower and higher membered heterocyclic rings, the necessity of a nearly linear arrangement of the involved centers in the hydrogen transfer step and a minimum of nonclassical strain in a cyclic 6-membered chair-like intermediate was postulated although the experimental evidence is not conclusive. 

Due to the perfect linear arrangement of the N-H -N hydrogen bridges in 13, extremely fast cooperative proton transfers occur in solution which... 

Qualitative models of reactivity and quantum mechanical calculations of reaction paths both indicate an angular approach of the attacking nucleophile to the first-row sp -hybridized electrophilic centers M at intermediate and reactive distances, 29. The geometry of 29 is also characteristic for the case of nucleophilic addition to electron-deficient centers of main-group 12 and 13 elements. By contrast, a linear arrangement 30 of making and breaking bonds is required for sp -hybridized first-row centers (C, N, O)... 

Confirmation of the linear arrangement came by physical techniques, especially electron diffraction and infrared spectroscopy. Later the nonequivalence of the nitrogen atoms in diazoaeetic ester was shown by means of labeling. ... 

A linear arrangement of electron pairs requires two hybrid orbitals, and so we mix an s-orbital with a /7-orbital to obtain two s/7-hybrid orbitals ... 

B Three cr bonds formed from two C2sp hybrids, one bond between the two C atoms and two connecting each C atom to an H atom in a linear arrangement two tt bonds, one between the two C2pv-orbitals and the other between the two C2pv-orbitals. 

Fig. 11. (Left) An outer core of 16 spherons surrounding an inner core of three, in a linear arrangement. (Right) The same core with a portion of the mantle of the elongated nucleus. (The difference in relative sizes of core and mantle spherons is exaggerated in this and some of the other figures.)...

The importance of the linear arrangement of mixer/funnel/tubular reactor is shown when processing in a set-up with a curved flow element (0.3 m long bent Teflon tube of 0.3 mm inner diameter) in between the funnel and tubular reactor [78]. If a straight tube of equal dimensions as given above is used, plugging occius after 30 s. Hence even short curved flow passages are detrimental for micro-chan-nel-based amidation studies. 

S02- ClF [70] and S02- HC1 [28,126] have negligible non-linearity of the halogen and hydrogen bonds, respectively, even though weakly bound. Examination of Fig. 10 reveals that the F5- and Cl5- are far away from the centre S 5+ in each case and that, therefore, the linear arrangements are to be expected. 

Since Ca is not directly surrounded by Ti atoms, the first polyhedron symbol is dropped however, the first comma cannot be dropped to make it clear that the 12co refers to a cuboctahedron formed by 12 O atoms. Ti is not directly surrounded by Ca, but by six O atoms forming an octahedron. O is surrounded in planar (square) coordination by four Ca, by two linearly arranged Ti and by eight O atoms forming a prism. 

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