Inertia defect calculations

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]. 

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... 

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. 

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]. 

Five isotopomers of Sia were studied in Ref (20), and are labeled as follows Si- Si- Si (I) Si- Si- Si (II) Si- Si- Si (III) Si- "Si- Si (IV) Si- Si- °Si (V). Rotational constants for each (both corrected and uncorrected for vibration-rotation interaction) can be found towards the bottom of Table I. Structures obtained by various refinement procedures are collected in Table II. Two distinct fitting procedures were used. In the first, the structures were refined against all three rotational constants A, B and C while only A and C were used in the second procedure. Since truly planar nuclear configurations have only two independent moments of inertia (A = / - 4 - 7. = 0), use of B (or C) involves a redundancy if the other is included. In practice, however, vibration-rotation effects spoil the exact proportionality between rotational constants and reciprocal moments of inertia and values of A calculated from effective moments of inertia determined from the Aq, Bq and Co constants do not vanish. Hence refining effective (ro) structures against all three is not without merit. Ao is called the inertial defect and amounts to ca. 0.4 amu for all five isotopomers. After correcting by the calculated vibration-rotation interactions, the inertial defect is reduced by an order of magnitude in all cases. 

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