Molecules, arranging demonstration

Our earliest attempt to model shock-induced chemistry with molecular dynamics was based on LEPS-like potentials, which were used to describe a nitric oxide chain with the NO molecules arranged head to tail and tail to head along the chain (NO, ON, NO,. ..). This approach was successful in demonstrating that chemically sustained shockwaves driven by exothermic reactions (in this case the half reactions N-t-NO—>-N2-t-0) could be modeled with molecular dynamics. However, the potential form assumed required a fixed number of nearest neighbors and hence was not readily generalized to higher dimensions. 

The tetrahedral arrangement of four bonds from B was established by the methods of classical stereochemistry. A molecule such as that of borosalicylic acid (1) would possess a plane of symmetry if the boron bonds were coplanar. The optical activity of this molecule was demonstrated by its resolution into optical antimers using strychnine as the active base. This really only eliminates a strictly... 

We have demonstrated that we can design pairs of chiral molecules with very similar size and shape but different donor or acceptor properties so that such pairs of molecules can cocrystallize to form a quasiracemic motif in which dipole moments or other physical properties need not cancel. This provides a rational strategy to design molecular crystals for practical applications. These successes provide further indication that molecular size and shape are controllable factors that direct how molecules arrange themselves in the... 

To code the configuration of a molecule various methods are described in Section 2.8. In particular, the use of wedge symbols clearly demonstrates the value added if stereodescriptors are included in the chemical structure information. The inclusion of stereochemical information gives a more realistic view of the actual spatial arrangement of the atoms of the molecule imder consideration, and can therefore be regarded as between the 2D (topological) and the 3D representation of a chemical structure. 

The nonmesogenic compound CB2 is described here, because it shows a reversible distortive solid-solid phase transition at 290.8 K (transition enthalpy 0.9 kj/mol) from the centrosymmetric low temperature phase I to the noncentrosymmetric high temperature phase II. The crystal structures of both solid phases I and II are very similar [45] as demonstrated in Fig. 2. The molecules are arranged in layers. The distances between the cyano groups of adjacent molecules are 3.50 A Ncyano-Ncyano and 3.35 A Ncyano-C ano for phase I and 3.55 A Ncyano-Ncyano and 3.43 A Ncyano-Ccyano for phase II. In the two... 

The suggestion of a helical host molecule was originally put forward by Hanes 136) and then developed by Freudenberg and his colleagues 137). Chemical 138 140) and X-ray diffraction studies by Rundle et al.141 143) and by Bear 144,145) demonstrated that these ideas were correct, and revealed that the helical structure had an outer diameter of 13.0 A, an inner diameter of 5 A, and a pitch of 8.0 A with six glucose units per turn. The iodine atoms were arranged in a linear fashion with an average I-I separation of approximately 3.1 A. These early results have been reviewed 146, 147). They represent the first confirmed example of helical structure for a biopolymer. 

No one prior to that time had been able to demonstrate with certainty what actual spatial arrangement of groups was in any chiral molecule. 

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