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He II photoelectron spectra of tetrahydrothiophen-2-one, tetrahydrothiophen-3-one and 2(5H)-thiophenone have been recorded along with the corresponding He I spectra. The relative He I/He II band intensities provide clear evidence for the assignment of the first few bands, which are also assigned on the basis of bandshape and SCF MO calculations. Correlations with IPs of tetrahydrothiophene, 2,5-dihydrothiophene and formaldehyde show that the interaction of the carbonyl group and the ring heteroatom is primarily inductive in nature in these thiophenones, though there may be a small degree of conjugative interaction between the carbonyl group and the ethylenic moiety in 2(5H)-thiophenone.

The valence electronic structures of the compounds γ-thionobutyrolactone (X=S,Y=O,R=R″=H), γ-butyrolactone (X=O,Y=O,R=R″=H) and their respective 3- and 5-methyl-substituted derivatives have been investigated by photoelectron spectroscopy. Two distinct bands are observed in the ionization potential (IP) range 8–11 eV in the spectra of all these compounds, with the first ionization band exhibiting clear vibrational progressions. Variation in the He I/He II relative intensities in the spectra of the γ-thionobutyrolactones suggests the assignment of the first band to the lone-pair ns orbital, the second band to theπ ocs * orbital and the third band to theπ ocs orbital. The first two bands in the spectra of the γ-butyrolactones, on the other hand, are ascribed to the nO(C O) and the ethereal no(π) orbitals, respectively. The assignments are aided by the results from semi-empirical PM3 and ab initio calculations using the 6–31G** basis sets. Correlation with the IPs of thioformaldehyde, cyclopentanone and tetrahydrofuran indicates that the interaction between the carbonyl group and the ring oxygen atom is mainly inductive in nature. In the γ-thionobutyrolactones, the conjugative interaction is more significant. Methyl substitution causes mainly inductive effects on the parent heterocyclics.

Most solid-phase microextraction methods are based on poly (dimethylsiloxane)-coated silica fibers. Is the present study, pencil lead was used as an alternative sorbent for solid-phase imcroextraction. Its application to three organic pollutants with different polarity in water was investigated. The detection limit for determination by gas chromatography with electron capture detector was 0.005 ng ml−1 for lindane, 0.05 ng ml−1 for methyl parathion and 1 ng ml−1 for 2-chlorophenol. The presence of dissolved humic substances (10 mg l−1) in water did not affect the extraction of the three analytes.

Orthogonal array desings were applied to the optimization of liquid chromatographic analysis of pesticides used in golf courses. Three variables related to the composition of the mobile phase were studied: the percentage of acetonitrile, percentage of methanol, and the buffer pH. In the first experiment, each variable was tested at three levels using an OA9 (34) matrix, in which the interactions between the parameters were temporarily neglected. Based on the results of the first experiment, the second experiment was carried out following a two-level orthogonal array design with an OA8 (27) matrix, in which more exact levels for each variable were chosen, and the interaction effects were considered separately. Finally, the optimum conditions for liquid chromatographic analysis of the pesticides were proposed. The advantages and the disadvantages of three-level and two-level orthogonal array designs were discussed.

Ethenethiol and 1-propene-1-thiol were produced through the thermolysis of thiirane and 2-methylthiirane, respectively, under reduced pressure in a flow system. The photoelectron spectra of the olefin thiols are characterised by the presence of a sharp first band which is well separated from the other bands by more than 2 eV. The spectra are discussed with the aid of AM1 and ab initio SCF MO calculations, and a diagram which correlates the binding energies of the first three orbitals, viz. π CCS * , π CCS and σ CS , with those of the corresponding orbitals of related molecules.

He I photoelectron spectra of title compounds were recorded and assigned by MNDO-PM3 calculations and comparison with spectra of related derivatives. Substituents were found to noticeably affect the electronic structure, depending on their type and position of attachment to the ring. MNDO-PM3 calculation results become unreliable in cases of thiophenes with widely different substituent types.

He II photoelectron spectra of isomeric bifurans and thienylfurans have been recorded and are assigned by comparing He I/He II intensity variations. The assignment agrees with the previous study of these molecules, where spectral interpretation was based on MO calculations and MO correlations within the title series. He I and He II spectra are reported for the new 3,3′-bifuran compound. Trends in the electronic structure within the bichalcophene series are discussed.

He * (2 3 S) Penning ionization electron spectra (PIES) of some nitroalkanes, nitropropenes and nitrobenzene have been recorded and compared with their respective He(I) photoelectron spectra (UPS). The spatial electron density distributions of the out-of-plane π orbitals of the nitro group are more extended than the in-plane n 0 orbitals, resulting in relatively strong π bands in the PIES. Similarly, the π CC bands of nitropropenes and the π ring bands of nitrobenzene are enhanced in the PIES owing to the more extended nature of these orbitals. This has enabled the unequivocal assignment of the first three ionic states of nitromethane. The assignment is also supported by multi-deference determinant configuration interaction (MRD-CI) calculations. Variations of the intensity enhancement among these compounds are discussed in terms of local steric shielding effects.

He(II) photoelectron spectra of nitromethane, nitroethane, 1- and 2-nitropropane have been recorded and compared with the corresponding He(I) spectra. The relative He(I)/He(II) spectral band intensities provide clear evidence for ascribing the first two maxima in the range 10–12 eV to ionization processes involving the removal of electrons from the orbitals n 0 + , n 0 − and π 2 . Similarly the band at ≈ 17 eV is attributed to ejection of electrons from the π 1 and σ NO − orbitals. Detailed assignment of spectral bands is made on the basis of bandshape and intensity, as well as ab initio SCF MO calculations using the 6-31G basis set. In the He(II) spectra, two bands in the region 18–22 eV are assigned to σ NO + and an orbital with 2s N and 2s O character.

Vertical ionization energies of the 1 : 1 molecular complexes of boron trifluoride with the three picolines and 3,5-lutidine are reported along with assignments based on their HeI photoelectron spectra and semi-empirical molecular orbital calculations. The shift in the lone pair (n N ) orbital of the donor molecules towards a higher ionization energy (IE) upon complexation is found to be essentially constant in all the complexes (nearly 2.8 eV) except in 3,5-lutidine·BF 3 where the shift is 3.3 eV. Such shifts in the IEs of the π orbital are about 1.1 eV for the 2- and 3-picoline complexes and 1.3 eV for the complexes of 4-picoline and 3,5-lutidine. These shifts reflect the relative stabilities of the complexes. The complex 2,6-lutidine·BF 3 undergoes dissociation into the free donor and acceptor molecules under the conditions of our experiment. A comparison of the shifts is made with the experimental heats of reaction of the pyridine bases with boron trifluoride. Relative stabilities of the complexes as deduced from ab initio and AM1 calculations are compared with predictions of gas-phase basicities of the bases.

Photoelectron spectroscopy has been employed to study the thermal decomposition of phenylnitromethane in the gas phase. The results indicate at least two processes for the decomposition. Thus at low temperatures ( ca. 400°C) water, nitric oxide and benzaldehyde are formed, together with a small amount of carbon monoxide. Possible pathways of reactions are discussed. The thermal decomposition of nitroethane has also been investigated.

The He I and He II photoelectron spectra of 2(3H)-furanone and 5-methyl-2(3H)-furanone have been recorded. They show a third band not reported earlier. The first three bands in the spectrum of 2(3H)-furanone at 9.76, 10.65 and 12.83 eV are assigned to ionizations from the π CC–O– *, n O(CO) , and π –O–CO * orbitals, respectively. Correlation with orbitals in ethene and acetic acid reveals significant π-conjugation in the furanones.