Inertia defects

The question of ring planarity has always been closely associated with the assignment of aromatic character to borepins, and a recently obtained microwave spectrum of 1-chloroborepin has allowed the derivation of its ground-state rotational constants. Calculation of the inertia defect (A = —0.19 uA2) from these data led to the conclusion that... 

There have been a large number of determinations of molecular force constants, mean amplitudes of vibration, bond asymmetry parameters, Coriolis coupling constants (and inertia defects) and centrifugal distortion constants [146,152,259,271,304,581,840,1221,1222,1278,1312, 1416,1448,1449,1549,1550,1575-1578,1587,1618,1671,1682,1806,1807,1858,1931,1961,1984,2021,2045, 2108,2109-2111,2167a], as well as a determination of the atomic potential energy distribution... 

Force constant and inertia defect calculations have been performed for COCIF [604,1312,1531,1549,1550,1575-1578]. CNDO calculations have been used to calculate (> C=0) for COCIF [1680], and the fundamental frequencies for COCIF have been calculated from the force constants calculated for COXj (X = F, Cl or Br) [1578]. 

For a planar molecule, the effective moments of inertia show a small positive inertia defect... 

The vibrational dependence of the inertia defect is given by formulas developed by Laurie and Herschbach20 and also by Oka and Morino21 involving the harmonic vibration frequencies and the Coriolis zeta constants ... 

Thus if the vibrational dependence of the inertia defect can be determined experimentally, either from the observation of microwave spectra in the ground and excited vibrational states or from high resolution vibration/rotation spectra, then this provides information on the Coriolis constants and hence on the forms of the normal coordinates and the harmonic force field. 

In practice, inertia defects have been used successfully as a source of information on the harmonic force field only for bent triatomic molecules, particularly for 03, S02, Se02, OF2, and similar molecules.14-16 For bent triatomics the vibrational inertia defect may be written in... 

NOTE The S r and the ground-state inertia defect were calculated and compared with those observed, but were not used directly in the force constant refinement. 

Geometric Structure. Inertia Defect Bond Distance. Bond Angle... 

Adopting the normal coordinate approach proposed in [12], the inertia defects A(PH3) = 0.132 amu-A2 and A(PD3) = 0.176 amu-A were derived [13] from the force field and fundamental frequencies in [14]. 

Pb(CD3)4 are 726xl0 and 569 x 10 cm respectively [47]. For centrifugal distortion constants, see [49]. The rotational branch structure to the skeletal fundamentals is studied and OR, RS branch separations are observed and compared with calculated values [35]. The PR separations are 15.7 and 13.9 cm respectively [47]. The inertia defect, bringing out the influence of vibration-rotation interaction on molecule structure was calculated and compared with that of other tetrahedral molecules [48]. 

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