Bent molecule

The solid is essentially ionic, made up of Pb and Cl ions. The vapour contains bent molecules of PbCh (cf. SnCh). Lead chloride is precipitated when hydrochloric acid (or a solution of a chloride) is added to a cold solution of a lead(ll) salt. It dissolves in hot water but on cooling, is slowly precipitated in crystalline form. It dissolves in excess of concentrated hydrochloric acid to give the acid H2[Pb"Cl4]. 

Tin(II) chlorides are similarly complex (Fig. 10.5). In the gas phase, SnCh forms bent molecules, but the crystalline material (mp 246°, bp 623°) has a layer structure with chains of comer-shared trigonal pyramidal SnClsl groups. The dihydrate also has a 3-coordinated structure with only I of the H2O molecules directly bonded to the Sn (Fig. I0.5c) the neutral aquo complexes are arranged in double layers with the second H2O molecules interleaved between them to form a two-dimensional H-bonded network... 

The nitrosyl halides are reactive gases that feature bent molecules they can be made by direct halogenation of NO with X2, though fluorination of NO with Agp2 has also been used and CINO can be more conveniently made by passing N2O4 over moist KCl ... 

Bent molecule Molecule containing three atoms in which the bond angle is less than 180° examples include H20 and S02,178 Benzedrine, 601 Benzene... 

Zareba et al. [165] described the crystal structure of the chiral 4-(l-methyl-heptyloxycarbonyl)-phenyl 4-heptyloxytolane-4 -carboxylate (C7-tolane) which shows monotropic antiferroelectric and ferroelectric phases. The single-crystal X-ray analysis of this compound shows that the crystal has a smectic-like layer structure composed of largely bent molecules where the chain of the chiral group is almost perpendicular (86°) to the core moiety. Within the layers, the molecules are tilted. The central tolane group of the molecule is roughly planar. 

By the argument in Section IIB, the presence of a locally quadratic cylindrically symmetric barrier leads one to expect a characteristic distortion to the quantum lattice, similar to that in Fig. 1, which is confirmed in Fig. 7. The heavy lower lines show the relative equilibria and the point (0,1) is the critical point. The small points indicate the eigenvalues. The lower part of the diagram differs from that in Fig. 1, because the small amplitude oscillations of a spherical pendulum approximate those of a degenerate harmonic oscillator, rather than the fl-axis rotations of a bent molecule. Hence the good quantum number is... 

We begin our exploration of delocalized bonds with ozone, O3. As described in Chapter 7, ozone in the upper stratosphere protects plants and animals from hazardous ultraviolet radiation. Ozone has 18 valence electrons and a Lewis stmcture that appears in Figure 10-36a. Experimental measurements show that ozone is a bent molecule with a bond angle of 118°. 

Ozone, which has 18 valehce electrohs, exemplifies bent molecules. Another example is the hitrite ahioh, the subject of Extra Practice Exercise. The bohdihg of NO2 can be represented using s p hybrid orbitals for the inner nitrogen atom and one set of delocalized n orbitals. 

Molecular compounds of bivalent tin are in all cases bent molecules, the angle between the substituents approaching 90°. Only the it-pseudo-bound cyclopentadienyl derivatives deviate considerably from this angle (120 and 144°, respectively) ... 

The very toxic sulfur(IV)-oxide, S02, is a bent molecule (C2v symmetry) that reacts as a reducing agent due to the higher stability of the oxidation state +VI for sulfur. S02 can be easily condensed to a colourless liquid (b.p. —10.0 °C) that has been shown to be a versatile solvent for several reactions, and below —75.5 °C a colourless molecular solid is formed. In the solid state, the S02 molecule shows a bond length SO of 1.429 A and an angle O-S-O of 119°.3... 

Each half-filled 4p orbital of Se overlaps with a half-filled Is orbital ofH to produce a bent molecule, with a bond angle of approximately 90°. 

The two most useful sets are the bond displacements themselves, and the symmetry coordinates. The use of the latter leads naturally to a scheme in which the Hamiltonian for bent molecules is no longer diagonal in the total 0(4) quantum numbers (ti, x2), and thus one loses the simple form of the secular equation (Figure 4.11). The secular equation must be now diagonalized in the full space with dimensions that become rapidly larger. This scheme, developed by Leviatan and Kirson (1988), can be implemented only if the vibron numbers N are relatively small, N < 10. 

An alternative approach, developed by van Roosmalen et al. (1982, 1983a), is based on the use of the bond coordinates, and treats bent molecules still keep-... 

The same rules for the reduction of representations of groups give the following content of angular momentum in each vibrational band of bent molecules... 

Figure 4.21 Rotational spectrum of a bent molecules, according to Eq. (4.107).

A similar treatment can be done for bent molecules in the scheme of van Roosmalen. The lowest-order, local-mode limit is given by... 

The rotation-vibration interaction of Section 4.32 produces different effects in nonlinear molecules than those discussed in the previous section. In nonlinear molecules the quantum numbers are vavhvcKJM >. The connection between the group quantum numbers Ico , co2> xi > 2 -A 3/ > and the usual quantum numbers is given by Eq. (4.85). The different effect can be traced to the different nature of the rotational spectrum. In lowest order, the spectrum of a bent molecule is given by Eq. (4.107) and Figure 4.21. The rotation-vibration interaction introduces terms with selection rules... 

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