Molecular orbitals reacting

Molecular ion (Section 13 22) In mass spectrometry the species formed by loss of an electron from a molecule Molecular orbital theory (Section 2 4) Theory of chemical bonding in which electrons are assumed to occupy orbitals in molecules much as they occupy orbitals in atoms The molecular orbitals are descnbed as combinations of the or bitals of all of the atoms that make up the molecule Molecularity (Section 4 8) The number of species that react to gether in the same elementary step of a reaction mechanism... 

Aromatic Radical Anions. Many aromatic hydrocarbons react with alkaU metals in polar aprotic solvents to form stable solutions of the corresponding radical anions as shown in equation 8 (3,20). These solutions can be analyzed by uv-visible spectroscopy and stored for further use. The unpaired electron is added to the lowest unoccupied molecular orbital of the aromatic hydrocarbon and a... 

Dinitrogen has a dissociation energy of 941 kj/mol (225 kcal/mol) and an ionisation potential of 15.6 eV. Both values indicate that it is difficult to either cleave or oxidize N2. For reduction, electrons must be added to the lowest unoccupied molecular orbital of N2 at —7 eV. This occurs only in the presence of highly electropositive metals such as lithium. However, lithium also reacts with water. Thus, such highly energetic interactions ate unlikely to occur in the aqueous environment of the natural enzymic system. Even so, highly reducing systems have achieved some success in N2 reduction even in aqueous solvents. 

Hydroxypyridine 1-oxide is insoluble in chloroform and other suitable solvents, and, although the solid-state infrared spectrum indicates that strong intermolecular hydrogen bonding occurs, no additional structural conclusions could be reached. Jaffe has attempted to deduce the structure of 4-hydroxypyridine 1-oxide using the Hammett equation and molecular orbital calculations. This tautomeric compound reacts with diazomethane to give both the 1- and 4-methoxy derivatives, " and the relation of its structure to other chemical reactions has been discussed by Hayashi. ... 

Simple resonance theory predicts that pentalene (48), azulene (49), and heptalene (50) should be aromatic, although no nonionic canonical form can have a double bond at the ring junction. Molecular orbital calculations show that azulene should be stable but not the other two, and this is borne out by experiment. Heptalene has been prepared but reacts readily with oxygen, acids, and bromine, is easily hydrogenated, and polymerizes on standing. Analysis of its NMR spectrum shows that it is... 

In a, P-unsaturated carbonyl compounds and related electron-deficient alkenes and alkynes, there exist two electrophilic sites and both are prone to be attacked by nucleophiles. However, the conjugated site is considerably softer compared with the unconjugated site, based on the Frontier Molecular Orbital analysis.27 Consequently, softer nucleophiles predominantly react with a, (i-unsaturated carbonyl compounds through conjugate addition (or Michael addition). Water is a hard solvent. This property of water has two significant implications for conjugate addition reactions (1) Such reactions can tolerate water since the nucleophiles and the electrophiles are softer whereas water is hard and (2) water will not compete with nucleophiles significantly in such... 

An unusual observation was noted when ethanolic solutions of 2-alkyl-4(5)-aminoimidazoles (25 R = alkyl) were allowed to react with diethyl ethoxymethylenemalonate (62 R = H) [92JCS(P1)2789]. In addition to anticipated products (70), which were obtained in low yield ( 10%), the diimidazole derivatives (33 R = alkyl) were formed in ca.30% yield. The mechanism of formation of the diimidazole products (33) has been interpreted in terms of a reaction between the aminoimidazole (25) and its nitroimidazole precursor (27) during the reduction process. In particular, a soft-soft interaction between the highest occupied molecular orbital (HOMO) of the aminoimidazole (25) and the lowest unoccupied molecular orbital (LUMO) of the nitroimidazole (27) is favorable and probably leads to an intermediate, which on tautomerism, elimination of water, and further reduction, gives the observed products (33). The reactions of amino-imidazoles with hard and soft electrophiles is further discussed in Section VI,C. 

TaCl2(PMe3)2]2(U-Cl)2 (13). The short metal-metal bond length of 2.710(2)A has been interpreted as a formal metal-metal double bond on the basis of molecular orbital arguments (13,14). An unusual feature of this complex is that it reacts with molecular... 

Dimethylfulvene 93 also reacts with sydnone 89, albeit sluggishly, to form the dihydrocyclopenta[c]pyrazole 94 after elimination of carbon dioxide and hydrogen (Equation 10). Molecular orbital energies and coefficients of 3-phenylsydnone 89 and fulvenes 91 and 93 have been calculated (PM3-MNDO), but when orbital symmetries... 

There is an equilibrium between the dimer and monomer, and molecular orbital study suggests that the heterochiral dimer is more stable than the homochiral isomer. The existence and behavior of the dimeric species were well confirmed by experiments such as cryoscopic molecular weight and NMR measurement. In the NMR study of a DAIB-catalyzed dialkylzinc addition reaction, noticeable changes were observed in the spectrum of the homochiral dimer on the addition of benzaldehyde, while the spectrum of the heterochiral complex remained the same. This may imply that the heterochiral complex is very stable and does not react, and the homochiral dimer leads to the reaction product. 

A heterogeneous catalytic reaction begins with the adsorption of the reacting gases on the surface of the catalyst, where intramolecular bonds are broken or weakened. The Appendix explains how this happens on metals in terms of simplified molecular orbital theory. Next, the adsorbed species react on the surface, often in... 

Hitherto, thio ether formation has clearly been proved only in the case of the ji-donor substituted 4-nitrosophenetol and the electron-rich l-methyl-2-nitrosoimidazole. The low yields of this adduct (about 2% at 1 1- and about 10% at 1 5-stoichiometry for 4-nitrosophenetol reacting with GSH56) may be the reason for its rare discovery. However, other nitrosoarenes should yield this family, too. Semiempirical molecular orbital calculations (MNDO) indicate a similar positive charge at the exposition of the N-(methylthiol-S -yl)-aniline cation and -4-anisole cation as well (Scheme 6). Furthermore, formation of l-(glutathion-S -yl)-2-naphthylamine was reported to occur in mixtures of 2-nitrosonaphthalene and GSH12. 

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