Yoshio Niwa

X‐ray photoelectron spectroscopy of tetraphenylporphin and phthalocyanine

The x‐ray photoelectron spectra of tetraphenylporphin, phthalocyanine and their copper complexes were measured. The copper complexes show a single nitrogen 1s photoline, whereas the metal free bases give rise to a doublet nitrogen 1s photoline. The central pyrrole and aza nitrogens in the metal free bases could be identified, whereas the central and meso‐bridging aza nitrogens in phthalocyanine could not be discriminated. Each of the central two protons in the metal free bases is localized on one of the central four porphinato nitrogens. The shifts in N 1s binding energy observed in the present work could be reproduced by the shifts in the charge density on nitrogen obtained for the bonded structure by an extended Huckel molecular orbital calculation.

Structural characterization of lipid A component of Erwinia carotovora lipopolysaccharide

The chemical structure of the lipid A component of lipopolysaccharide excreted into the liquid medium by the plant pathogenic enterobacterium Erwinia carotovora FERM P-7576 was characterized. It consists of a β-1′, 6-linked glucosamine disaccharide which carries ester-and amide-bound fatty acids and phosphate similar to the lipid A from other gram-negative bacteria. The lipid A preparation was not uniform in the number and composition of the fatty acids linked to the disaccharide. Four prominent lipids A were involved, they were composed of five to seven residues of fatty acid. Among them the major component was hexa-acyl lipid A, in which the hydroxyl group at position 3′ and the amino group of the non-reducing glucosamine unit carry 3-dodecanoyl-oxytetradecanoyl residues. Positions 2 and 3 of the reducing glucosamine unit were substituted by 3-hydroxytetradecanoic acid. In the hepta-acyl lipid A, an additional hexadecanoic acid was linked to the hydroxyl group of the 3-hydroxytetradecanoyl residue at position 2 of the hexa-acyl lipid A. Two penta-acyl lipids A were the homologs of the hexa-acyl lipid A with decreasing acylation. Dodecanoic acid was missing from one, and 3-hydroxytetradecanoic acid from another. 3-Dodecanoyloxytetradecanoyl residue at position 3′ differentiates E. carotovora lipid A from that of other gram-negative bacteria.

Ionic dissociation of methanol studied by photoelectron–photoion coincidence spectroscopy

Ionic dissociation of methanol has been investigated by means of photoelectron–photoion coincidence spectroscopy. Breakdown curves and average kinetic energies released in the fragmentations were obtained as a function of molecular ion internal energy. In the CH2OH+ formation about 45% of the excess energy available for the dissociation is converted into translational energy of products. In contrast, the average translational energies released in the formation of CH3+ and HCO+ ions are 0.4 and 2.5 eV, respectively, and these values remain constant irrespective of the excess internal energy over the excited states of ions, 6a′−1, 1a″−1, and 5a′−1. All results including the breakdown curves reveal that the statistical theories of unimolecular decomposition can not give a satisfactory interpretation to mass spectra of methanol. Alternative mechanisms are discussed to account for the observations.

Structural identifications of straight-chain fatty acids and esters in coal extracts by linked scanning mass spectrometry

Abstract Structural identifications of geochemically significant straight-chain fatty acids and esters in coal extracts were carried out by linked scanning mass spectrometry together with field desorption mass spectrometry. The results obtained demonstrate the usefulness of the technique for direct analysis of complex mixtures to elucidate detailed molecular structures of individual constituents. The extracts of lignites contain straight-chain fatty acids with C 24 to C 34 and long-chain fatty esters with C 48 to C 64 , the latter being missing from subbituminous coals and neither is found in those of bituminous coals. The free fatty acids, the acyl and the alkoxyl groups of esters all extend from C 24 to C 34 and are qualitatively similar to each other in carbon-number distribution indicating that they were probably derived from common precursor compounds. The presence and/or absence of fatty acids and fatty esters parallels the rank of coals and may be connected with chemical changes brought about during maturation, such as hydrolysis of the esters, conversions of the acids into paraffins, etc.

Bimodal kinetic energy release in the unimolecular dissociation of energy‐selected formic acid ion

Dissociation of HCOOH+ and DCOOH+ have been studied using threshold photoelectron–photoion coincidence (TPEPICO) mass spectrometry. The detailed breakdown diagrams were obtained over internal energies of the molecular ion less than 8 eV. Kinetic energy release distributions (KERDs) for HCO+ and DCO+ were extracted from their flight time distributions by using a multiple linear regression method. The breakdown curve of HCO+ not only exhibited several maxima but also the surprisal analysis of its KERD demonstrated a considerable deviation from a single statistical distribution. Bimodal KERDs were observed for the formation of HCO+ and DCO+. The large KER component results from dissociation to the products in the ground state, HCO+ (1Σ+)+⋅OH (2Πi). Average kinetic energy releases observed for this process are, however, about twice higher than those calculated by QET/RRKM. The small KER component shows average KERs remarkably smaller than the statistical expectations and this value remains constant over the e...

On the dissociation dynamics of energy-selected dimethylether ions

Abstract Dissociation of the dimethylether ion has been studied using threshold photoelectron-photoion coincidence (TPEPICO) mass spectrometry. Our TPEPICO breakdown curves showed a significant occurrence of electronic autoionization at around 12.2 eV and over 16 eV. For the formation of [CH 3 O] + , rectangular flight-time distributions owing to a large, sharp kinetic energy release were observed at high energies, and about 80% of internal excess energy of the molecular ion was found to be released as translational energy in this fragmentation. This remarkably high conversion was consistent with the spectator model of direct dissociation rather than with statistical theories (RRKM—QET). However, the relative abundance of [CH 3 O + ] remained less than 20% in the breakdown diagram although direct dissociation predicts its predoiminace. These results may be intepreted as a direct dissociation to CH 3 O + on a repulsive state reached by transition from an initial state or as a statistical fragmentation to CH 2 O + H strongly controlled by a tight transition exit on a high reverse activation barrier.

The Fragmentation of Skeletal Bonds in the Mass Spectra of Higher Normal Alkanes

Mass spectra of normal tridecane CisHu and hexadecane OieHu were measured over a wider range of ionizing voltage and temperature of the ion source than hitherto reported. In both alkanes, the amount of the O3 and O4 fragments decreased gradually as the ionizing voltage and the temperature were lowered, though both fragments are especially abundant compared with other fragments in all the higher normal alkanes under ordinary measuring conditions. This finding could be explained quantitatively under the assumption that fragmentations can be classified into two processes ; i. e., the fast process and the slow process, and that the MO theory is applicable to the fast process*, while the statistical theory applies to the slow process. Several general problems in the application of the present theory are discussed as well as the relation to other theories on the fragmentation process.

Difference molecular ion spectrum method for reaction analysis of complex mixtures

Abstract A difference molecular ion spectrum method based on field-ionization mass spectrometry is proposed for the study of chemical reactions of complex mixtures such as coal liquefaction, hydrogenation treatment of coal-derived liquids, etc. The method allows reaction schemes to be elucidated and an evaluation of the activities of catalysts and the degree of hydrogenation of the liquefaction solvents.

IONIC CLUSTERS OF TRIAZINE DERIVATIVES PRODUCED BY MATRIX-ASSISTED N 2 LASER DESORPTION AND CO 2 LASER DESORPTION

Mass spectra of ions from the pyrolytic product of cyanuric trichloride and ammonia were obtained by matrix-assisted N 2 laser desorption time of flight mass spectrometry (TOF -MS) and CO 2 laser desorption Fourier transform mass spectrometry (FT-MS). Cluster ions of which chemical formulae are expressed by C x N 2 x-y H 2 x -3 y +1 + were found and were assigned as a series of ionic clusters of triazine oligomers.

Investigation on chemical structures of heavy polar materials in wandoan coal-derived liquid. Chemical structures of nonpolar products from hydrocracking of heavy polar materials.

The stepwise hydrocracking of heptane-soluble polar fraction (Po) and asphaltene (As) isolated from wandoan coal-derived residue was carried out over a presulfided Ni-Mo/Al2O3 catalyst at 375 °C to investigate their chemical structures. Five nonpolar samples (Po/NP, Po/Po/NP, As/NP, As/As/NP, As/Po/NP) were obtained from the hydrocracking products as shown in Fig. 1.The nonpolar products (Po/NP, As/NP) from the first hydrocracking of Po and As had lower molecular weights than those (Po/Po/NP, As/As/NP, As/Po/NP) from the second hydrocracking of the recovered polar materials. Each nonpolar product was separated into seven compound-types by HPLC equipped with a semipreparative Bondapak-NH2 column. Fr.3 and Fr.6 were analyzed by field ionization mass spectrometry (FIMS). The same compound-type fractions were shown to con-sist of similar polycyclic hydroaromatic structures, although those from the second hydrocracking have more naphthenic rings which resulted in higher molecular weights.