Tarja Laitalainen

Reversed-phase high-performance liquid chromatographic screening method for serum steroids using retention index and diode-array detection

A multisteroid screening method has been developed based on the use of 1-[4-(2,3-dihydroxypropoxy)phenyl]-1-alkanones as retention index standards and UV absorbance spectra recorded on-line with a diode-array detector using reversed-phase high-performance liquid chromatographic gradient elution with acetonitrile and water. The effect of chromatographic conditions on retention indices of steroids were studied. The method was tentatively applied to profiling of steroids in serum samples.

Influence of secondary bonding on the intradimer distance of trichloro(ethane-1,2-diolato-O,O′)tellurate(IV)

The structure of ammonium trichloro(ethane-1,2-diolato-O,O′)tellurate(IV) was determined by single-crystal methods: monoclinic, space group P21/c(no. 14), a= 10.779(1 ), b= 12.418(2), c= 6.915(1)A, β= 108.65(1)°. The co-ordination around TeIV is distorted ψ octahedral with one of the two oxygen atoms lying opposite to the lone pair of Te. Two identical anions form a dimeric unit via a centre of symmetry. A short Te–O intradimeric distance of 2.764(6)A is about 0.84 A shorter than the sum of the corresponding van der Waals radii. The structure is compared with that of the corresponding tetraphenylphosphonium salt where the intradimer distance is clearly longer. The size of the cation and the amount of intermolecular interactions seem to be decisive factors in secondary bonding between two anionic units. The electronic properties of the anions in the two salts were investigated by ab initiocalculations and compared with those of the optimised structure of the corresponding monomeric anion. The positive charge of 1.36 electrons at Te is almost invariable. The main interaction within a dimeric unit in the ammonium salt is a donation of an electron pair from oxygen to the antibonding molecular orbital between Te–Cl in the neighbouring anion. The bond between Te and one of the equatorial Cl atoms (opposite to oxygen) is sensitive to dimerisation. The charge density, ionic nature of the bond and bond length increase when the degree of dimerisation increases, whereas the other two Te–Cl bonds are almost insensitive.

STEREOSPECIFIC SYNTHESIS AND CRYSTAL STRUCTURE OF THE RACEMATE OF 1-THIA-2-TELLURA-1(1-ALLYL-4-CHLORO)CYCLOPENTANE 2,2,2-TRICHLORIDE

Abstract Tellurium tetrachloride and diallyl sulfide react to stereospecifically formed crystals of 1-thia-2-tellura-1(1-allyl-4-chloro)cyclopentane 2,2,2-trichloride. According to single-crystal X-ray determination the structure consists of the (R,R)-(S,S) racemate unit with a centre of symmetry. In the asymmetric units the TeIV-atoms display distorted ψ octahedral coordination. Although the equatorial Te-S bond length is 2.763(1) A, the Natural Bond Order (NBO) analysis reveals significant electronic interaction.

Stereoselective synthesis, molecular structure and NBO analyses of cis-3,5-di(chloromethyl)-1,4-oxatellurane(IV) 4,4-dichloride

Abstract Tellurium tetrachloride and diallyl ether give stereoselectively cis-3,5-di(chloromethyl)-1,4-oxatellurane(IV) 4,4-dichloride. The structure was determined by single crystal X-ray diffraction. The coordination around the TeIV ion is a distorted Φ trigonal bipyramid with two chlorine atoms in the axial positions. Two of the equatorial sites are occupied by carbon atoms, with the lone electron pair located at the third position. The six-membered heterocycle displays a chair conformation. The crystal structure consists of ribbons with Te·Cl contaacts. The NBO (Natural Bond Order) analyses carried out by both HF/STO-3G∗ and HF/LANL1DZ level of theory gave different results. No intermolecular interaction (>1 kcal mol−1) was found by HF/STO3G∗, whereas the main interaction can be seen between a lone pair of Cl(2) and the antibonding orbital between Te(1) and C(1) by RHF/LANL1DZ (1.1 kcal mol−1).

Formation of 1,3-oxaselenoles via Pummerer reaction in selenium dioxide oxidation of cyclic 1,2- and 1,3-diketones, and the preparation of 1,5,5-trimethyl-7-selenabicyclo [2.2.1] heptane-2,3-dione

4,5,6,7-Tetrahydro-4′,4′,6,6-tetramethylspiro[1,3-benzoxaselenole-2,1′-cyclohexane]-2′,4,6′-trione and related 1,3-oxaselenole derivatives, and not the previously reported selenoxides of type (1), are formed in the selenium dioxide oxidation of cyclohexane-1,3-dinoes. The structural assignments were made on the basis of n.m.r. spectroscopy, and in the case of (5), X-ray analysis was undertaken. Oxidation of 3,3,5,5-tetramethylcyclohexane-1,2-dione with selenium dioxide yielded the bis-selenide (9) and the 1,3-oxaselenole (10) along with the usual oxidation products, whereas the oxidation of 3,5,5-trimethylcyclohexane-1,2-dione gave the title, bridged selenabicyclic compound.