Carbon orbital structure

Because of the necessity of spatially appropriate overlap of the 2p. .-orbital on boron with the adjacent jp3-hybridized carbon orbital (12) or with the tt-MO of the double bond (13), any such ir-bonding should be most sensitive to molecular conformation. Hence, the occurrence of such 7r-bonding might be more evident in certain highly rigid cyclic structures, such as 14 and 15. 

The relative rate of isobutane isomerization has been shown by Anderson and Avery 24) to be markedly increased by using a (111) platinum film surface. On the other hand, this did not occur with n-butane, nor did it occur with either iso- or n-butane over a (100) platinum surface (cf. Table II). A triangular array of adjacent sites on a (111) platinum surface can be readily fitted by an adsorbed isohydrocarbon, and this structure also fits to allow the carbon orbitals to be directed normally to the surface. On simple geometric grounds, this adsorbed structure is specific to the (111)/... 

Returning to the transition metal monocarbides, Figure 5.6 now provides a more familiar correlation diagram showing the hybridization between metal orbitals and carbon orbitals to produce the monocarbides with the NaCl structure. The p-orbitals are shown as being composed of the pxpy and pz orbitals where the, y, and z axes are now relative to some arbitrary plane in which the x and y axes are parallel to this plane and the z axis is its normal. Relative to the same plane, the d-orbitals are split into... 

Considering the hybridization of carbon orbitals, which of the following structures is least likely to exist ... 

There was much affinity between Coulson and Barriol, not only because of the many subjects they shared, but also because of their similar way of proceeding and thinking. They both conceded a high value, in many respects, to the determination of dipole moments. Both worked on methane (CH4) and more particularly on the dipole moment of the C-H group, for which Coulson gave a direction when Barriol s simple model could not. [25] It is highly interesting to compare the way how the two authors express themselves to show that experience or physical and chemical evidence had to correct the false inferences or deductions that square in no way with reality the description of the carbon electronic structure fails to account for four equivalent bonds. We have to admit that the C-orbitals that are... 

The Patemo-Buchi reaction on furan has been studied from a theoretical point of view [42]. The HOMO of furan has an energy of 0.32 eV, and the atomic coefficients of this orbital (Fig. 3.3) are in agreement with an attack of the carbonyl oxygen on the a carbon. The structures of the possible adducts deriving from the attack of benzaldehyde in the a position of furan are depicted in Figure 3.4. The exo isomer is more stable (0.5 kcal mol 1) than the other isomer, in agreement with the experimental results. 

The hybridization and bond angles of a simple carbanion also resemble those of an amine. The carbon atom is sp3 hybridized and tetrahedral. One of the tetrahedral positions is occupied by an unshared lone pair of electrons. Figure 4-16 compares the orbital structures and geometry of ammonia and the methyl anion. 

Buckminsterfullerene (Ceo) is a third elemental form of carbon. Its structure consists of 20 hexagons and 12 pentagons of sp hybridized carbon atoms joined in a spherical arrangement. It is completely conjugated because each carbon atom has a p orbital with an electron in it. 

The basic display returned by the action of the Isomers command button is shown in Figure 1.18. The aim of the calculation is to determine the numbers and symmetries of isomeric structures resulting from addition or substitution of vertices. For example, if we take an underlying single orbit of vertices as, say, carbon atoms, then decorations x, xx, xy, xxx... tell us about the isomers CnX, CnX2, CnXY, CnXs and so on, where each X, Y,... is attached to a distinct carbon atom of the orbit, while decoration of multiple-orbit structures extends the analysis to a large variety of other cages and clusters. 

Problem 10.4 The molecules of pyridine CsHsN, are flat, with all bond angles about 12(P. All carboir-carbon bonds are 1.39 A long and the two cai bon nitrogen bonds are 1.36 A long. The measured heat of combustion is 23 kcal lower than that calculated by the method of Problem 10.2 on page 323. Pyridine undergoes such substitution reactions as nitration and sulfonation (Sec. 10.4). (a) Is pyridine adequately represented by formula I (b) Account for the properties of pyridine by both valence-bond and orbital structures. (Check your answer in Sec. 31.6.)... 

When the metal is niobium, the two metal frontier orbitals, dy and dz2, are closer in energy and match the corresponding orbitals of triplet free carbene. Figure 10-4b provides a picture of the interactions involved (only the important orbital interactions are shown). The elections in the M-C bond are much more equally distributed between the metal and Ccarbene (because the energy levels of the metal and carbon orbitals are comparable) than with an electrophilic carbene complex. In resonance terminology, this means that structure 10 becomes an important contributor to the overall structure of this particular Schrock carbene complex.11... 

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