The electronic states of nitroanilines

A correlation of spectroscopic data with all-valence-electron, $\text{CNDO}\text{s-CI}$ results has been performed for a number of mono- and disubstituted benzenes containing nitro and/or amino groups. The lowest energy transitions of p-nitroaniline are predicted to be 1¹B₁ ← 1¹A₁, 2¹A₁ ← 1¹A₁, and 2¹B₁ ← 1¹A₁, in the order of increasing energy. These three transitions are assigned to (i.e., are encompassed within) the lowest energy absorption band envelope of p-nitroaniline. The lowest energy predicted transition of o- and m-nitroanilines is 2A′ ← 1A′ and is supposed to correspond to the totality of the lowest energy absorption feature in both of these systems. The orbital excitation nature of these transitions is discussed.     

Photoelectron spectroscopy of azulenes

The photoelectron spectra of azulene and ten of its derivatives (halo-, methyl-, phenyl-, acetyl- and benzoylazulenes) are presented and assigned. Assignments based on a composite-molecule view are validated by computations (CNDO/S). Conjugative interactions in the phenylazulenes lead to an inversion of the usual order of the two phenyl group e_1g component orbitals. Many of the azulenes have very low ionization energies, and it is suggested that they constitute a class of excellent π-electron donor molecules.     

Molecular Rydberg transitions: Cyanogen chloride

The electronic absorption spectrum of cyanogen chloride has been investigated in the range 2200-1250 Å. The first s-Rydberg transitions, $\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}\text{→}{}^3\text{Π}{}_1$ and $\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}\text{→}{}^1\text{Π}{}_1$ have been assigned, and analyzed to yield exchange and spin-orbit coupling parameters. The relative intensities of these two transitions have been shown to accord with an intermediate coupling situation. The $\text{π → π}{}^1$ intravalence excitations, leading to ^1.3(Σ^?, Δ and Σ⁺) states, have been discussed. It has been shown that one or both of the ¹Σ^? and ¹Δ states have bent geometries and that the ¹Σ⁺ state is located (tentatively) at 79 755 cm^?1. Two $\text{σ → π}{}^1\text{π → σ}{}^1$ states have been assigned, one at 56 340 cm^?1, the other at 74 450 cm^?1. The latter assignment is tentative, being largely based on observed vibronic interferences between the $\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}\text{→}{}^1\text{Π}{}_1$ transition and the 74 450 cm^?1 transition. A considerable amount of vibrational oscillator strength and quantum defect data is presented.     

Ab initio calculations on 5α-androstane

The electronic structure of 5α-androstane, the parent hydrocarbon of the hormonal steroids, has been computed by ab initio SCF methods in an STO -3G basis. The results are compared with existing MNDO computations and are used to discuss long-range electronic interactions between distant substituents that might be appended to rings A and D of 5α-androstane. It is thought that these interactions are mediated by the ribbonlike MO 'S of the parent molecule.     

Catalytic asymmetric Staudinger reactions to form beta-lactams: an unanticipated dependence of diastereoselectivity on the choice of the nitrogen substituent

There are relatively few methods for the catalytic asymmetric synthesis of beta-lactams, and those that have been reported are generally cis selective. This communication describes the first catalytic enantioselective Staudinger reactions that preferentially furnish trans beta-lactams (trans = relationship of Ph to R1). The key to this method is the use of an N-triflyl protecting group for the imine. Along with serving as interesting targets in their own right, N-triflyl beta-lactams readily react with nucleophiles to generate useful families of compounds, such as gamma-amino alcohols and beta-amino acids.     

Electronic absorption spectrum of Ba(MnO4)2·3H2O/Ba(ClO4)2·3H2O

Polarized absorption spectra of Ba(MnO₄)₂·3H₂O/Ba(ClO₄)₂·3H₂O mixed single crystals are reported at 4.2°K. Previous ¹T₂ → ¹A₁ assignments for the 5200 Å and 3000 Å absorption bands of MnO₄⁻ are substantiated; further support is provided for the ¹T₁ → ¹A₁ assignment of the 3600 Å absorption band of MnO₄⁻. The site-splitting of the 5200 Å ¹T₂ state is E(¹E)−E(¹A) ≈ −150 cm⁻¹; that of the 3000 Å ¹T₂ state is E(¹E)−E(¹A) ≈ 300 cm⁻¹. A significant e vibronic intensity component is observed in the 5200 Å ¹T₂ state.     

PHOTOLYSIS OF SOME CYCLIC DISULFIDES*

Abstract— Photolysis of liquid pentarnethylene disuliide, liquid tetramethylene disulfide and liquid l, 4-butanedithiol has been studied. Photolysis of the cyclic disulfides by irradiation in their lowest energy absorption band produces the corresponding dithiol; photolysis of alkali-doped cyclic disulfide at the same irradiation wavelength as above produces the corresponding cyclic monosulfide. It is suggested that photolysis of undoped liquids proceeds via -S-S- scission, whereas that of the doped liquids is supposed to involve initial -CS- scission. Photolysis of the dithiol produces the corresponding cyclic monosulfide, the rate of such production being considerably enhanced in the presence of alkali. Much of the above data and suggestions are rationalized using a simple MO formalism, which also involves an attempted interpretation of much of the electronic spectra of the various compounds. Product identification was made by study of the short wavelength absorption spectrum of the vapor in equilibrium with the photolysed material.