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Sigma bond symmetry

A sigma bond has cylindrical symmetry along the bond axis => rotation of groups joined by a single bond does not usually require a large amount of energy => free rotation. [Pg.35]

Both sigma bonds and pi bonds have a kind of symmetry with respect to the two atoms in the bond. What is the difference in a sigma bond s symmetry versus a pi bond s symmetry ... [Pg.69]

A sigma bond is a molecular orbital that looks like an s-type atomic orbital when viewed down its axis and has cylindrical symmetry. A tt bond looks like a p-type of atomic orbital from the same... [Pg.50]

The problem may be restated in terms of the symmetry of all of the orbitals involved. In the transition state the pair of electrons forming the sigma bond to hydrogen may now be considered part of the n system the hydrogen will move suprafacially or antarafacially depending on whether the HOMO is a or b. For (4n + 2)77- electrons a thermal change is allowed, and for (471)77- electrons a first-excited-state process is allowed. [Pg.236]

The a (sigma) bond has its maximum electron density along the line-of-centers joining the two atoms (below left). Viewed end-on, the u bond is cylindrically symmetrical about the line-of-centers. It is this symmetry, rather than its parentage, that defines the sigma bond, which can be formed from the overlap of two s-orbitals, from two p-orbitals arranged end-to-end, or from an s- and a p-orbital. They can also form when... [Pg.45]

Because of rapid rotations about sigma bonds and molecular symmetry, the three methyl hydrogens are all equivalent to each other. For the same reasons the two methylene protons are also equivalent to each other. In summary,... [Pg.691]

An idealized single bond is a sigma bond—one that has cylindrical symmetry. In contrast, a p-orbital or pi-bond orbital has pi symmetry—one that is antisymmetric with respect to reflection in a plane passing through the atomic centers with which it is associated. In ethene, the pi-bonding orbital is symmetric with respect to reflection in a plane perpendicular to and bisecting the C-C bond, whereas the pi-star-anti bonding orbital is antisymmetric with respect to this operation. [Pg.201]

Such two-center orbitals may take part in molecular orbitals of sigma or pi symmetry. For example, the methyl group in propene contains three C-H bonds, each of which is of local sigma symmetry (i.e., without a nodal plane including the internuclear axis), but these three sigma bonds can in turn be combined to form a set of group orbitals, one of which has pi symmetry with respect to the principal molecular plane and can accordingly interact with the two-center orbital of pi symmetry (pi bond) of the double-bonded carbon atoms to form a molecular orbital of pi symmetry. [Pg.245]


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See also in sourсe #XX -- [ Pg.11 ]

See also in sourсe #XX -- [ Pg.11 ]

See also in sourсe #XX -- [ Pg.10 ]




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