Triangular molecules

For example, in a plane triangular molecule such as BF3, each of the twofold symmetry axes lying in the plane can be carried into coincidence with each of the others by rotations of 27r/3 or 2 x 2nl3, which are symmetry operations. Thus all three twofold axes are said to be equivalent to one another. In a square planar AB4 molecule, there are four twofold axes in the molecular plane. Two of them, C2 and C2, lie along BAB axes, and the other two, C and Ci, bisect BAB angles. Such a molecule also contains four symmetry planes, each of which is perpendicular to the molecular plane and intersects it along one of the twofold axes. Now it is easy to see that C2 may be carried into C2 and vice versa, and that C2 may be carried into C2 and vice versa, by rotations about the fourfold axis and by reflections in the symmetry planes mentioned, but there is no way to carry C2 or C into either CJ or Cn or vice versa. Thus C2 and C2 form one set of equivalent axes, and and C form another. Similarly, two of the symmetry planes are equivalent to each other, but not to either of the other two, which are, however, equivalent to each other. 

The B atom has an incomplete octet in all its trihalides. The compounds consist of planar triangular molecules with an empty 2p-orbital perpendicular to the molecular plane. The empty orbital allows the molecules to act as Lewis acids, which accounts for the catalytic action of BF3 and BC13. 

The triangular molecule has [21,22] two normal vibrational coordinates that span two irreducible representations A. In order to diagonalize the nuclear kinetic and potential energy we solve the classical problem of normal vibrations. In this way one obtains two A coordinates... 

The distance between end atoms is 2.38 A, slightly greater than the value 2 X 1.16 = 2.32 A between end atoms in COj. Here again we see the resemblance between Nj and CO, in that they form similar molecules when another oxygen atom is added. The molecule SO is a triangular molecule shaped something like water. Its structure presumably is... 

This is a planar (flat) and triangular molecule, which is commonly described as trigonal planar. 

Is H3 a linear or a triangular molecule For both the linear and equilateral triangular configurations, apply a variant of the Hiickel theory based on hydrogen li-orbitals (rather than carbon 2p) to predict which has the lower energy. Also predict the shapes of the ions and. ... 

For example, in a triangular molecule X3, if the electronic state belongs to an E representation and only a doubly degenerate e mode is considered, we can obtain the following Jahn-Teller effect with the quadratic vibronic coupling... 

JT systems with strong coupling, and some efficient approaches have been formulated in the theory of so-called non-rigid molecules. The triangular molecule has two normal vibrational coordinates that span two irreducible representations, Ai and 5i. The normal vibrational modes Qb and = qAi of the FeNO fragment... 

C0, and NO3, and the neutral SO3 molecule, all of which are planar triangular molecules or ions. An equilateral triangular structure is, of course, only to be expected if all the ligands are of the same kind deviations from bond angles of 120° occur in less symmetrical molecules such as COCI2 or O2NF. 

Figure 3.11 Space group diagrams for planar group pi (a) symmetry elements (b) equivalent general positions (c) position of a triangular molecule motif (d-f) specification of the coordinates (x, y) of an atom...

Ozone is a triangular molecule with a bond distance of 1.27 A, and a bond angle of 117°. This could be compared with the bond distance in the double bonded O2 molecule, 1.21 A, or to the single bond in HOOH, 1.46 A. We conclude that partial double bonds are formed between the end and central oxygen atoms. How can we explain this One would expect the ozone molecule to be a bi-radical because the end atoms can only use one of their free valencies to form a bond with the central atom. But ozone is not a biradical, even if it is quite reactive. The radical structure is quite high in energy and there are ionic structures that may compete. We show the three most important valence structures in Fig. 25.6. 

Filipe, E. J. M. Deiters, U. K. Calado, J. C. G. Liquid mixtures involving triangular molecules (vapour + liquid) equilibria of (xenon-Mrimethylboron)/. Chem. Thermodyn. 1998,30, 1543-1553... 

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