Orbital symmetric

Withdrawal of electrons from orbitals symmetric between hydrogen atoms (generally inductive effects) should lead to a positive change in the coupling constants. ... 

In the case of conrotatory mode, the symmetry is preserved with respeo to C2 axis of rotation. On 180° rotation along this axis, F goes to H. and H2 to H, and the new configuration is indistinguishable from the original. An orbital symmetric with respect to rotation is called a and antisymmetric as b. On the other hand, in the case of disrotatory moot-the elements of symmetry are described with respect to a mirror plane. Tilt symmetry and antisymmetry of an orbital with respect to a mirror plant of reflection is denoted by a and a" respectively (Section 2.9). The natun of each MO of cyclobutene with respect to these two operations is shov. n in the Table 8.4 for cyclobutene and butadiene. 

The above argument about the structure of N2O4 is based upon the assumption32 that the odd electron of N02 occupies a orbital symmetric in the plane of the nuclei) rather than a r orbital (antisymmetric). The alternative assumption has been proposed 33 with it the N—N bond would be described as a t bond without an associated a... 

It is interesting to note that the method of molecular orbitals leads to identical results, but by a rather different route. In this method we consider first the set of orbitals on the atoms surrounding the central atom. If this set consists of orbitals symmetrical about the line joining each external atom to the central atom, then these external orbitals form a basis for a representation of the symmetry group which is identical with the o- representation. The reduction of this representation then corresponds to the resonance of these external orbitals among themselves. The formation of molecular orbitals then takes place by the interaction between these reduced external orbitals and the orbitals of the central atom. This interaction can only take place, however, between orbitals belonging to the same representation. Hence, to obtain a set of molecular orbitals equal in number to the... 

The possibilities of double or triple bond formation are most easily discussed in terms of molecular orbitals. The principal type of multiple bond consists of two parts first, a pair of electrons in an orbital symmetrical about the axis of the bond and second, one or more pairs of electrons in orbitals which are not symmetrical about the axis. The first pair of electrons form a bond which differs in no way from the ordinary single, or passed through the axis. They may be regarded as formed by the interaction of two p orbitals, one on each atom, with axes parallel to each other and perpendicular to the axis of the bond. We shall refer to orbitals of this type as rr orbitals. 

Ethylene, the first member of the series, is already familiar. Two adjacent p orbitals interacting will yield a bonding orbital, symmetric with respect to reflection in the mirror plane lying midway between the two carbons and perpendicular to the C—C axis, and an antibonding orbital antisymmetric with respect to that mirror plane. Figure 10.18 illustrates the interaction and the resulting orbitals. 

Figure 12. The term diagrams for the Cu(II)-0, complex of various configurations determined by the angles and 4 0 defined in the top drawing. The symmetry labels A and A" denote orbitals symmetric and antisymmetric with respect to the reflection plane of the Clh group at = 30° and — 90°. The individual orbitals at = 90°, <, — 44°, G/ — 2300 cm 1, and Gt = 1800 cm 1 have the following form ...

Section 4-3-3 g for gerade, orbitals symmetric to inversion, and u for ungerade, orbitals antisymmetric to inversion (those whose signs change on inversion). The g or m notation describes the symmetry of the orbitals without a judgment as to their relative eneigies. 

The use of the remaining orbitals is shown in Fig. 5. We take the in-phase combination of the two iron a-orbitals as empty (Fig. 5a) and let the resultant orbital, symmetrical (a ) in the reflection place C, overlap the CO lone pair. The resulting three-centre bond is entirely analogous to the three-centre bonds in Al2(CHa)6 or [Be(CHa)2]n, in which the MCM angle is also anomalously small 43. 44). 

Screening length of orbital Symmetric orbital Antisymmetric orbital Symmetric p-type orbital Antisymmetric p-type orbital Angle... 

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