Cellular-indecomposable subnormal operators II

This work continues that begun in [9]. Our investigation has led us to the following conjecture: a cyclic subnormal operator is cellular-indecomposable if and only if it is quasi-similar to an analytic Toeplitz operator whose symbol is a weak-star generator of H. In this paper some particular cases of the conjecture are verified.This work was supported in part by a grant from the National Science Foundation.     

Simulated distillation of wax samples using supercritical fluid and high temperature gas chromatography

Simulated distillation boiling range distributions have been compared for high boiling petroleum wax samples using high temperature gas chromatography and supercritical fluid chromatography. Midpoint (50 % off) temperature differences were small, and average differences between the two types of analyses were less than 6° Details of optimization of the HTGC and SFC systems and injection techniques used are reported.     

Structure of plumbazeylanone: a novel trimer of plumbagin from plumbago zeylanica

Plumbazeylanone, a quinone from Plumbago zeylanica is probably 5b,11a,12,12a-tetrahydro-1,7-dihydroxy-5b-(8-hydroxy-3-methyl-1,4-naphthoquinon-2-yl)-5a,12a-dimethyl-5a$\text{H}$-dibenzo[$\text{b}$,$\text{h}$]fluorene-5,13:6,11-diquinone, a novel trimer of plumbagin with an additional methyl group.     

Basis set dependence of the calculated geometry of HNCO

SCF calculations of the equilibrium geometry of HNCQ have been carried out using gradient techniques and a wide variety of basis sets. it is concluded that 3d functions are essential for reliable geometry predictions in this and related isocyanates.     

Optimisation of polystyrene resin-supported Pt catalysts in room temperature, solvent-less, oct-l-ene hydrosilylation using methyldichlorosilane

Six precursor resins with systematic variation of porous parameters were prepared by suspension polymerisation using specific compositions of divinylbenzene, styrene vinylbenzyl chloride (VBC) and 2-ethylhexan-l-ol (a porogen). Surface areas from N(2) sorption and BET analysis were approximately 2-170 m(2)g-(1). The VBC content in each case was 38 mol% and these groups were aminated using the sodium salt of trimethylethylene diamine. Pt was introduced onto each resin at three different loadings (approximately 0.03, approximately 0.2 and approximately 0.4 mmol g-(1)) by appropriate manipulation of K(2)PtCl(6). The matrix of 18 resin-supported Pt complexes was then assessed for catalytic activity in the room temperature, solvent-less, hydrosilylation of oct-l-ene using methyldichlorosilane such that alkene: silane: Pt ratio was fixed at 2:1:1x10(-3). Though all the catalysts showed activity lower than that of homogeneous Speier s catalyst, most were sufficiently active to be potentially valuable heterogeneous catalysts in the laboratory, and indeed the plant. The most lightly loaded resins proved to be the least active. The remainder were recycled 5 times, and the best performers, the most highly loaded species, a further 5 times making 10 consecutive uses in all. A strong dependence on the porous structure of the resins was demonstrated with the activity rising systemically with the surface area. The two highest surface area highest loaded species displayed good activity even when used for the tenth time. The level of concurrent alkene isomerisation observed was very low throughout (<1%) making these heterogeneous species very selective as well as highly active. Overall the derived catalysts are excellent candidates for use in the research laboratory, and with further development could also be valuable in continuous processes.     

Electronic structure of unstable intermediates

The geometry of the species OCC has been investigated within the restricted Hartree-Fock LCAO-MO-SCF approximation. Several one electron properties have been calculated at the calculated minimum energy configuration of R(O-C)=2.121 bohr, R(C-C)=2.58 bohr.     

Oxidative behaviour of 3-aryl-2H-1,4-benzoxazines

Autoxidation of 3 - phenyl - 2H - 1,4-benzoxazine 8 gives 2 - hydroxy -3 - phenyl - 2H - 1,4-benzoxazine 13, 3 - phenyl - 2H - 1,4-benzoxazin - 2 - one 11, and 2 - phenylbenzoxazole 10 according to the conditions. Oxidation of 8 with DDQ in the presence of air gave mainly the bisacetal 17 but in the absence of air the major product was trans-Δ^2,2′-bi-(3-phenyl-2H-1,4-benzoxazine) 21a. Corresponding dimers were obtained from the 3-p-bromophenylbenzoxazine 9. The trans-isomers 21a and 22a are photochromic and change into their cis-isomers on exposure in solution to direct sunlight.     

Biquinones—IV : Addition of hydrogen halides to bibenzoquinones

The dienone structure (12; R = Ac) has been assigned to the diacetate of the product obtained by addition of hydrogen chloride to 4,4′-dimethoxy-2,5,2′,5′-biquinone, in the cold, mainly on the basis of its ¹³C NMR spectrum. The structures of a number of halogenodibenzofurans derived from this biquinone, and from the corresponding dimethylbiquinone, by reaction with hydrogen halide have also been determined.     

Synthesis and Properties of Diuridine Phosphate Analogues Containing Thio and Amino Modifications

Several analogues of diuridine phosphate (UpU) were synthesized in order to investigate why replacing the 2'-hydroxyl with a 2'-amino group prevents hydrolysis. These analogues were designed to investigate what influence the 2'-substituent and 5'-leaving group have upon the rate of hydrolysis. All the analogues were considerably more labile than UpU toward acid-base-catalyzed hydrolysis. In the pH region from 6 to 9, the rate of hydrolysis of uridylyl (3'-5') 5'-thio-5'-deoxyuridine (UpsU) hydrolysis rose, in a log linear fashion, from a value of 5 x 10(-)(6) s(-)(1) at pH 6 to 3200 x 10(-)(6) s(-)(1) at pH 9, indicating that attack on the phosphorus by the 2'-oxo anion is rate-limiting in the hydrolysis mechanism. In contrast, the rate of uridylyl (3'-5') 5'-amino-5'-deoxyuridine (UpnU) hydrolysis fell from a value of 1802 x 10(-)(6) s(-)(1) at pH 5 to 140 x 10(-)(6) s(-)(1) at pH 7.5, where it remained constant up to pH 11.5, thus indicating an acid-catalyzed reaction. The analogue 2'-amino-2'-deoxyuridylyl (3'-5') 5'-thio-5'-deoxyuridine (amUpsU) was readily hydrolyzed above pH 7, in contrast to the hydrolytic stability of amUpT, with rates between 85 x 10(-)(6) s(-)(1) and 138 x 10(-)(6) s(-)(1). The hydrolysis of 2'-amino-2'-deoxyuridylyl (3'-5') 5'-amino-5'-deoxythymidine (amUpnT) rose from 17 x 10(-)(6) s(-)(1) at pH 11.5 to 11 685 x 10(-)(6) s(-)(1) at pH 7.0, indicating an acid-catalyzed reaction, where protonation of the 5'-amine is rate limiting. The cleavage rates of UpsU, UpnU, and amUpsU were accelerated in the presence of Mg(2+), Zn(2+), and Cd(2+) ions, but a correlation with interaction between metal ion and leaving group could only be demonstrated for amUpsU. UpsU and UpnU are also substrates for RNase A with UpsU having similar Michaelis-Menten parameters to UpU. In contrast, UpnU is more rapidly degraded with an approximate 35-fold increase in catalytic efficiency, which is reflected purely in an increase in the value of k(cat).