Antibonding orbitals for

These simple charge or orbital interactions may be enough to explain simple inorganic reactions but we shall also be concerned with nucleophiles that supply electrons out of bonds and electrophiles that accept electrons into antibonding orbitals. For the moment accept that polar reactions usually involve electrons flowing from a nucleophile and towards an electrophile. 

The C-O a (antibonding) orbital for the a anomer is of lower energy than the corresponding axial C-H orbital for the (3 anomer. The overlap of the lone-pair /i-orbital is therefore more efficient in the a anomer than in the (3 anomer. 

Table 3.8 gives semiempirical expressions for the direct spin-spin part of several effective spin-spin constants and some numerical examples for valence states of homonuclear molecules where the n orbital is assumed to be an antibonding orbital. For Rydberg states, the contribution of the Rydberg n orbital can be neglected. 

The activation energy for 5 2 attack can be correlated with bond distances—the shorter the bond, the higher the activation energy, which is consistent with poor acceptor property of an S antibonding orbital for the incoming nucleophile in reactions such as... 

Bonding and antibonding orbitals for the molecule. Two electrons, with opposite spins, are shown in the bonding orbital. 

Likewise, the corresponding member of and 2e will fall in energy since they are antibonding orbitals. For convenience wo have rotated our coordinate system for the octahedron by 45 to that in 15.35. The components of the important t2g set will now be A z, and yz. Let us concentrate on yz. At the octa-... 

The orbital interactions underlying this type of sulfur-mediated carbanion stabilization are somewhat subtle and are best described as a form of hyperconjugation. An examination of the highest occupied molecular orbital (HOMO) shows that the tr-antibonding orbitals for the C-S bonds parallel to the carbanion lone pair (shown in red below) are able to delocalize the negative charge ... 

Further bond order reduction can be achieved by continuing to populate the metal-metal antibonding orbitals. For example, Ru2(02C-C3H7)4Cl with its a 7T 8 8 7T electron configuration has a bond order of 2.5 the corresponding bond length is 2.281 A. Total population of the... 

All of these examples have been cases in which all of the valence d electrons on each metal atom have paired in either bonding or antibonding orbitals. For zero-valent metal carbonyl dimers only one of the many valence d electrons on each metal is shared hence, only single bonds are known for these systems. The reason why the earlier transition metals in nonzero valent oxidation states form up to quadruple bonds and the later zero-valent transition metal carbonyls form only single bonds can be understood by considering the electronic needs of these different metal centers. 

One last reaction type that is commonly encountered is electron transfer to a it or u bond. This bond must be capable of receiving a negative charge, and it is common for these bonds to have electronegative atoms. Since the electron transfer is to an intact bond, the newly added electron goes into an antibonding orbital for that bond. In the case of an alkene or carbonyl, this can be denoted by the creation of a anion radical with the two species drawn on separate atoms. For a a bond, however, it is difficult to designate where the electron went, and we simply draw a radical anion next to a dashed bond. 

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