Crystalline hydrogen bonded adducts of oxygen bases with peroxybenzoic acids

The preparation and isolation of several crystalline 1 : 1 adducts of substituted peroxybenzoic acids with triphenylphosphine oxide, triphenylarsine oxide, and pyridine oxides, is reported. Infrared spectra indicate the presence of strong intermolecular hydrogen bonds in these adducts.     

Polyurethane foam of the polyether type as a solid polymeric extractant for cobalt and iron from thiocyanate media

By combining instrumental and radiochemical neutron activation analysis, up to 47 elements including major, minor, and trace elements, have been determined in lake sediment samples. Instrumental neutron activation involving both short and long irradiations is used to determine 40 elements including most of the environmentally important ones. A radiochemical separation procedure allows the determination of 7 noble metals. The accuracy and precision of the method are 5–10%.     

Energy and angular differential cross sections for K + NO2 charge transfer reactions

Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO^?₂ in its ground ¹A₁ and excited ³B₁ state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO^?₂.     

Synthesis of 2,3,4-trideoxy-4-c-(phenylphosphinyl)-dl-glycero-pentofuranose and its 1,5-diacetate

Synthesis of 2,3,4-trideoxy-4-C-(phenylphosphinyl)-dl-glycero-pentofuranose (11) starting from 2-furanmethanol was successful. The reaction of methyl 2,3-dideoxy-(1S)-dl-pentopyranosid-4-ulose 4-(p-toluenesulfonylhydrazone) with methyl phenylphosphonite gave methyl (4RS)-2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-4-C-(p-toluenesulfonylhydrazino)-(1S)-dl-pentopyranoside (7), which on treatment with sodium borohydride afforded methyl 2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-(1S)-dl-glycero-pentopyranoside (9). Treatment of compound 9 with SDMA followed by hydrolysis and treatment with acetic anhydride-pyridine afforded 1,5-diacetate 12 of compound 11.     

Interpretation and measurement of oxygen Kα emission spectra

Evidence concerning the true shape of the oxygen Kα emission band is summarised and new measurements of the reflectivity spike of KAP analysing crystals in this region presented. A new interpretation of the oxygen emission band is proposed which largely reconciles conflicts in previous interpretations: a broad region of real but low intensity emission spans the 531 eV region and is enhanced by at least five times by the KAP reflectivity spike. Emission spectra corrected for enhancement are illustrated and compared with those obtained with a clinochlore analysing crystal. Possible origins of emission in this region are discussed along with evidence concerning its changing intensity relative to other parts of the emission band as the incident electron energy is altered during primary excitation. Direct measurements of the oxygen K absorption spectrum for the silicate mineral vermiculite indicate that such relative changes in intensity are not due to partial overlap of emission and absorption spectra as was previously thought.     

The multiphoton ionization spectrum of toluene in a supersonic free jet: internal rotation of the methyl group

The S₁← S_o electronic transitions of toluene involving also some internal rotational levels were observed for the first time in the multiphoton ionization spectrum in a supersonic jet. A large population in several low-lying internal rotational levels and a strong coupling between electronic motion and the internal rotation are suggested.     

Cycloaddition of diphenylnitrilimine to coumarins. The synthesis of 3a,9b-dihydro-4-oxo-1H-benzopyrano [4 ,3-c]pyrazole derivatives

The cycloaddition of diphenylnitrilimine to a series of coumarins occurs with the same regioselectivity in all cases, regardless the nature of the substituent present, to yield the corresponding 3a,9b-dihydro-4-oxo-lH-benzopyrano [4,3-c]pyrazoles $\text{4}$a–f. Dehydrogenation of $\text{4a}$ yields 4-oxo-1H-benzopyrano [4,3-c]-pyrazole $\text{6}$. In ethanolic sodium ethoxide solution, the reaction between coumarin and diphenylnitrilimine precursor, namely N-phenylbenzohydrazidoyl chloride $\text{1}$, affords no cycloadducts, but yields o-(β-ethoxycarbonylvinyl)phenyl N-phenylbenzohydrazidate $\text{10}$. The regiochemistry of the cycloadducts $\text{4}$a–f and the reaction sequence leading to $\text{10}$ are outlined. The structures of the products have been established by spectroscopic methods and independent syntheses wherever possible.     

The role of the solvent in equilibrium and kinetic aspects of metal chelate extractions

Equilibria and kinetics for the extraction of nickel(II) and copper(II) by 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N) in seven organic solvent systems were studied in order to test the validity of several hypotheses related to the role of the solvent in equilibrium and kinetic aspects of metal chelate extraction. For the nickel—LIX 65N system, the extraction constant is essentially independent of the solvent system, whereas for the copper—LIX 65N system, the extraction constant is not independent of solvent; this indicates that while the stoichiometry of the nickel chelate remains the same in all solvents, that of copper does not. The observed rate constant for the nickel—LIX 65N extraction was found to vary inversely with the LIX 65N distribution constant as predicted from a mechanism involving slow formation of the 1:1 complex. The observed reaction rate constant for the copper—LIX 65N varied inversely with the square of the distribution constant, also in accordance with the previously postulated mechanism of the slow formation of the 2:1 copper complex. This study, therefore, unequivocally eliminates the interfacial mechanism in favor of the homogeneous chemical reaction mechanism for the extraction of metal ions by LIX 65N, as well as by other similar high-molecular-weight extractants.     

Localized states in molecular auger spectra

The influence of the degree of localization of the two final holes on the Auger spectra of a simple diatomic molecule is analysed in detail and cases where such effects may be observed experimentally are discussed. The results are compared with studies of the valence band Auger spectra of solids.     

Synthesis of mevalonolactone (hiochic acid lactone) employing asymmetric epoxidation as the key-step

(R)( — )-Mevalonolactone (hiochic acid lactone)of 91–93%e.e. was synthesized from an achiral starting material employing the Sharpless asymmetric epoxidation as the key-step.     

High-resolution IR spectrum of fluoroform: a close resonance

A very close triple resonance is observed in the Q-branch region of the C-H stretching fundamental transition in CF₃H. The vibrational perturbations are analysed in terms of the rotational structure and of the vibrational zero-order spectrum of totally symmetric states. The relationship to time-dependent intramolecular processes is discussed.     

A thermal lensing study of a photolysis of di-t-butyl peroxide

A photolysis of di-t-butyl peroxide (BOOB) was studied by using a thermal lensing technique. This technique is found to be applicable to the determination Of the rate Constants of the decay of t-butoxy radical (BO ) and the hydrogen abstraction reaction.     

Effects of geometric distortions and substituents on rates of intersystem crossing; diazomethane and pyrazoline

We report a qualititive perturbation-theoretic analysis of the effects of substituents on the spin-orbit coupling and on the density of states in diazomethane and pyrazoline systems. The importance of the form of the distortion which accompanies approach to the singlet-triplet crossing zone is also discussed with the aim of determining when reactions involving a spin multiplicity change can compete in rate with spin-conserving reactions.     

Pavoninins,shark-repelling and ichthyotoxic steroid n-acetylglucosaminides from the defense secretion of the sole pardachirus pavoninus (soleidae)

Six steroid itN-acctylglueosaminides, pavoninins-1 to -6, have been isolated from the defense secretion of the sole P. pavoninus guided by ichthyotoxicity and hemolytic activity, and their structures determined to be 1–6 by spcctroscopic studies and chemical correlations. The pavoninins are considered to be the factors responsible for the repellent property of the sole against predatory fishes.     

Methyl group hopping reorientation and the non-existence of spin symmetry species at room temperature

A series of experiments is discussed which, it has been claimed, demonstrate that hindered methyl groups exist at room temperature as relatively long-lived proton spin symmetry species. It is concluded that this concept lacks a theoretical foundation, conflicts with the model of random hopping reorientation between localised states, and leads to physically implausible predictions.     

Diels-alder reactions of substituted maleic anhydrides with 1-vinylcoclohexane: Stereospecific formation of a bicyclic intermediate useful for syntheses of clerodane diterpenes

The Diels-Alder reaction of 1-vinylcyclohexene with aconitic anhydride gives the adduct 5b which has the reversed stereochemistry of that predicted by Alder's endo rule. On the other hand, reactions with chloromethylmaleic anhydride and citraconic anhydride afford endo-adducts 23 and 24, respectively. Adduct 23 has the appropriate stereochemistry and functionality for the syntheses of clerodane and related diterpenes.     

Infrared and Raman multi-phonon spectra and structure of PbWO4

Improved Raman spectra of PbWO₄ show previously reported spectra contain large polarization and/or orientation errors. New spectroscopic information, obtained from polarized IR reflection and Raman spectra, allowed us to assign the IR and the previously unreported Raman multi-phonon bands. It was also used to show that it determines uniquely the C_4h factor group of PbWO₄. The use of IR reflection vs. infrared transmission spectra in the vibrational determination of crystal structures is also discussed.