Pyramidal acetone

Pyramidal Acetone-Like Molecules Without the Cog-Wheel Effect... 

Finally, let us consider once more the acetone molecule, but in a pyramidal configuration with the oxygen atom outside the CCC plane. Acetone exhibits this configuration in the lowest triplet state. In addition, pyramidal acetone may undergo an inversion phenomenon or wagging of the oxygen atom up and down the CCC plane. 

WU and VU possess exactly the same commutation properties with respect to the remaining group elements as W and V, because the operation U commutes with all of them. U acts indeed only on variable a. Therefore, the pyramidal acetone NRG (48) possesses the same group structure and the same character table as the NRG of acetone, just as it happens in planar and non-planar pyrocatechin. This is given in Table 8. 

Table 8 Character Table for the double internal rotation and wagging in pyramidal acetone with interaction between the moving parts.

FVom this character table, and the symmetry eigenvectors of planar acetone (54-56), the symmetry eigenvectors of pyramidal acetone are easily deducible. For this purpose, linear combinations of the eigenvectors, which exhibit the same behavior for all the operations except for WU and VU, are built up. In addition, to the coefBcients of which are trigonometric functions of the wagging angle, a. The coefficients are chosen in such a way that the linear combinations fulfill the characters corresponding to operators WU and VU,... 

It is noticeable that the NRG theory developed here furnishes two different groups for the double rotation in planar pyrocatechin (or acetone), and the double rotation and wagging mode in non-planar pyrocatechin (or pyramidal acetone). The group structures, however, are seen to be the same. The Longuet-Higgins theory yields indeed the same Molecular Symmetry Groups for both pyramidal uid planar systems. As a result, the NRG theory is seen to furnish a more det ulled information about the dynamics of the non-rigid systems. 

The pyramidal acetone-like molecules, such as acetone in an electronic excited state, dimethylamine, yield good examples of applications of the local groups to Czv rotor molecules. As in non-planar pyrocatechin, three different local Hamiltonian operators may be considered. 

In the present work, simple analytical forms were deduced for the potential energy functions of single rotation in phenol (22), of double rotations in benzaldehyde (25) pyrocatechin (30), and acetone (47), of double rotation and inversion in non-planar pyrocatechin (41) and pyramidal acetone(52). Approximate potential energy functions were proposed for some of these non-rigid systems in the local Hamiltonian approach (75), (80), (84), (86), (90) and (96). 

In the same way, the minimal expansions are seen to be built, in the case of rigid pyramidal acetone, or dimethylamine, with only ten terms, using (59) [35,491 ... 

In the present paper, symmetry eigenvectors which factorize the Hamiltonian matrix into boxes are given for the single rotation in phenol (24) for double rotations in benzaldehyde (29), pyrocatechin (34) and acetone (44-46), for double rotation and inversion in non-planar pyrocatechin (40) and pyramidal acetone (49-51). In the same way, symmetry eigenvectors deduced in the local approach are deduced for some of these non-rigid systems (79), (83), and (89). Symmetry eigenvectors for the double internal Czv rotation in molecules with frame of any symmetry are given in reference [36]. 

To classify the torsional states of both electronic states, the irreducible representations corresponding to the rNRG, 36 for pyramidal acetone (48) has to be used ... 

Aminophenol. This compound forms white plates when crystallized from water. The base is difficult to maintain in the free state and deteriorates rapidly under the influence of air to pink-purple oxidation products. The crystals exist in two forms. The a-form (from alcohol, water, or ethyl acetate) is the more stable and has an orthorhombic pyramidal stmcture containing four molecules per unit cell. It has a density of 1.290 g/cm (1.305 also quoted). The less stable P-form (from acetone) exists as acicular crystals that turn into the a-form on standing they are orthorhombic bipyramidal or pyramidal and have a hexamolecular unit (15,16,24) (see Tables 3—5). 

Five-coordinate Ni111 complexes (89) have been prepared by oxidation of the square planar Ni11 precursor complexes [Ni(L)X] with either X2 or CuX2, and the crystal structure of the iodo derivative has been determined. The geometry at Ni is best described as square pyramidal, with the Ni atom displaced approximately 0.34 A out of the basal plane towards the apical I atom. EPR confirms the Ni111 oxidation state, in which the unpaired electron of the low-spin d1 system is situated in the dz2 orbital.308,309 In aqueous solution full dissociation of both X anions occurs, while in acetone solution dissociation is not significant. The redox couple [Nin NCN (H20)]+/ [Ni111 NCN (H20)ra]2+ in water is +0.14V (vs. SCE). 

Tetraethylammonium pentachloroindate(lll) is a white crystalline solid, mp 285° (dec.), slightly soluble in ethanol at 20° (more so at the boiling point) and also soluble in acetone and dichloromethane. The IR7,8 spectrum shows absorptions at 294 (s), 282 (s), 268 (s), 152 (sh), and 142 cm 1 Raman emissions have been reported9,10 at 294 (s), 287 (sh), 194 (w), 167 (m), 123 (m), and 106 (m) cm"1. The crystal structure determination11,12 shows that the anion is essentially square-based pyramidal, an unusual stereochemistry for main group elements MX5 species. 

The compound PPN[Ru5N(CO) 4] is obtained as orange-red crystals. The solid is stable in air for short periods, but it should be stored under an inert atmosphere. It is soluble in diethyl ether, THF, acetone, and dichloromethane, and insoluble in hexane and water. The IR spectrum of a THF solution exhibits the following carbonyl stretching absorptions 2060 (w), 2013 (vs), 1999(s), 1960(m), 1820(m)cm-1. The square pyramidal geometry of ruthenium atoms has been established by X-ray crystallography.2... 

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