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At least 145 records · Page 8Linked to original sources
PubMed2001

Headspace gas chromatographic determination of 2-alkyl-5,5-dimethyl-1,3-dioxane derivatives in wastewaters of a polyester resin plant.

The static headspace gas chromatographic technique can be conveniently employed to check the presence and amount of the odorous side-products, 2-R-1,3-dioxanes (R = H, CH3, C2H5, i-C3H7, n-C3H7), directly from the wastewaters flowing from the reactors during the synthesis of polyester resins. By the optimisation of a simple and direct analytical method, the amounts of these compounds may be continuously monitored and controlled. This method is characterized by good repeatability (3-4%) and does not seem to suffer from matrix effects. The detection limits for the determination of the five dioxanes fall in the range 400-700 micrograms dm-3 (alpha = beta = 0.05).

Journal Article↗
PubMed2005

The first hyperpolarizability of p-nitroaniline in 1,4-dioxane: a quantum mechanical/molecular mechanics study.

In this work we have investigated the first hyperpolarizability of pNA in 1,4-dioxane solution using a quantum mechanics/molecular mechanics (QM/MM) model. The particular model adopted is the recently developed discrete solvent reaction field (DRF) model. The DRF model is a polarizable QM/MM model in which the QM part is treated using time-dependent density-functional theory and local-field effects are incorporated. This allows for direct computation of molecular effective properties which can be compared with experimental results. The solvation shift for the first hyperpolarizability is calculated to be 30% which is in good agreement with the experimental results. However, the calculated values, both in the gas phase and in solution, are by a factor of 2 larger than the experimental ones. This is in contrast to the calculation of the first hyperpolarizability for several small molecules in the gas phase where fair agreement is found with experimental. The inclusion of local-field effects in the calculations was found to be crucial and neglecting them led to results which are significantly larger. To test the DRF model the refractive index of liquid 1,4-dioxane was also calculated and found to be in good agreement with experiment.

Journal Article↗
PubMed2001

Supramolecular structures of 5-[3-(4-methylphenyl)- and 5-[3-(4-chlorophenyl)-2-propenylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione.

2,2-dimethyl-5-[3-(4-methylphenyl)-2-propenylidene]-1,3-dioxane-4,6-dione, C16H16O4, crystallizes in the triclinic space group P-1, with two molecules in the asymmetric unit. These molecules and a centrosymmetrically related pair, linked together by weak C-H...O hydrogen bonds, form a tetramer. 5-[3-(4-Chlorophenyl)-2-propenylidene]-2,2-dimethyl-1,3-dioxane-4,6-dione, C15H13ClO4, also crystallizes in the triclinic space group P-1, with one molecule in the asymmetric unit. Centrosymmetrically related molecules are linked together by weak C-H...O hydrogen bonds to form dimers which are further linked by yet another pair of centrosymmetrically related C-H...O hydrogen bonds to form a tube which runs parallel to the a axis.

Journal Article↗
PubMed2002

2,3,6,7-Tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene bis(1,4-dioxane) solvate.

2,3,6,7-Tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene crystallizes with 1,4-dioxane to give a bis-solvate, C(18)H(18)O(4).2C(4)H(8)O(2). The bis(catechol) molecule is located on a twofold axis and the two aromatic rings form a dihedral angle of 130.61(4) degree. Hydrogen bonds are formed between the hydroxyl groups and either a neighbouring bis(catechol) molecule or the ether-O atom of a dioxane molecule.

Journal Article↗
PubMed2002

N,N'-Dithiobisphthalimide-1,4-dioxan (1/0.6): a C2/c solvate with disordered solvent molecules localized in channels.

N,N'-Dithiobisphthalimide crystallizes from 1,4-dioxan solution as a solvate, 3C(16)H(8)N(2)O(4)S(2) x 1.8C(4)H(8)O(2), having space group C2/c. Four of the 12 C(16)H(8)N(2)O(4)S(2) molecules in the unit cell lie on twofold rotation axes, while the other eight lie in general positions. These molecules are linked by aromatic pi-pi-stacking interactions and by C[bond]H...O hydrogen bonds to form a framework enclosing continuous channels running parallel to the [101] direction, which account for ca 20% of the unit-cell volume. The dioxan molecules lie in these channels disordered across two sets of sites, with one set across an inversion centre and the other across a twofold rotation axis.

Journal Article↗
PubMed2002

Tetrameric triphenylsilanol, (Ph(3)SiOH)(4), and the adduct (Ph(3)SiOH)(2)-dimethyl sulfoxide, both at 120 K, and the adduct (Ph(3)SiOH)(4)-1,4-dioxan at 150 K: interplay of O[bond]H...O and C[bond]H...pi(arene) interactions.

The structure of tetrameric triphenylsilanol, C(18)H(16)OSi, (I), has been re-investigated at 120 (2) K. The hydroxyl H atoms were readily located and one of the arene rings is disordered over two closely positioned sets of sites. The molecules are linked into cyclic tetramers, having approximate 4 (S(4)) symmetry, via O[bond]H...O hydrogen bonds [H...O 1.81-1.85 A, O...O 2.634 (3)-2.693 (3) A and O[bond]H...O 156-166 degrees ]. At ambient temperature, there are indications of multiple disorder of the phenyl-ring sites. In bis(triphenylsilanol) dimethyl sulfoxide solvate, 2C(18)H(16)OSi x C(2)H(6)OS, (II), the dimethyl sulfoxide component is disordered across a twofold rotation axis in C2/c, and the molecular components are linked by a single O[bond]H...O hydrogen bond [H...O 1.85 A, O...O 2.732 (2) A and O[bond]H...O 172 degrees ] into three-molecule aggregates, which are themselves linked into a single three-dimensional framework by two C[bond]H...pi(arene) interactions. In tetrakis(triphenylsilanol) 1,4-dioxan solvate, 4C(18)H(16)OSi x C(4)H(8)O(2), (III), the 1,4-dioxan component lies across an inversion centre in space group P-1 and centrosymmetric five-molecule aggregates are linked by paired C[bond]H...pi(arene) interactions to form molecular ladders.

Journal Article↗
PubMed2004

Desorption kinetics of a xanthenol-dioxane clathrate.

The host xanthenol compound forms a 1:1 clathrate with dioxane, namely 9-(1-naphthyl)-9H-xanthen-9-ol-1,4-dioxane, C23H16O2.C4H8O2. The structure of this clathrate is reported, along with a study of the kinetics of desolvation and the determination of an activation energy. The guest molecules are stabilized by O(host)-H...O(guest) hydrogen bonds [O-H = 0.968 (2) A, O...O = 2.7532 (13) A and O-H...O = 151.9 (4) degrees].

Journal Article↗
PubMed1971

Study on dioxan separation in the radioimmunoassay of human growth hormone, human chorionic gonadotrophin, adrenocorticotrophic hormone, and insulin.

The dioxan precipitation for separating free from antibody-bound hormone in a radioimmunoassay has been applied to human chorionic gonadotrophin (HCG), human growth hormone (HGH), adrenocorticotrophic hormone (ACTH), and insulin and compared with the charcoal-dextran system of separation. The dioxan separation depends on protein concentration. The behaviour of damaged labelled hormone is difficult to assess. Completeness of separation has to be tested in antigen excess. The optimum conditions must be carefully studied for each hormone.

Adrenocorticotropic Hormone↗
PubMed1972

"Plasmalogen-type" cyclic acetals: formation and conformation of the 1,3-dioxanes and 1,3-dioxolanes from 1-0-cis-alk-1'-enyl-sn-glycerols.

Acid-catalyzed cyclization of 1-O-cis-alk-1'-enyl-sn-glycerol produced four structurally and geometrically isomeric long-chain cyclic acetals of glycerol. The isomers were isolated by adsorption and gas-liquid chromatography and were identified as cis-2-alkyl-5-hydroxy-1,3-dioxane (Ia), trans-2-alkyl-5-hydroxy-1,3-dioxane (IIa), cis-2-alkyl-4-hydroxymethyl-1,3-dioxolane (IIIa), and trans-2-alkyl-4-hydroxymethyl-1,3-dioxolane (IVa). The structure of each isomer was established by chemical and spectroscopic methods. Cyclization with p-toluenesulfonic acid in boiling benzene led to a thermodynamically equilibrated mixture of isomers Ia-IVa in which the cis isomers predominated. Cyclization in acetic acid was found to be kinetically controlled, and formation of the trans isomers was relatively favored. Rearrangement of the cyclic acetal isomers did not occur in acetic acid; hence, optically active five-membered ring acetals were prepared.

Acetals↗
PubMed2001

1,4-dioxane-fused 4-anilinoquinazoline as inhibitors of epidermal growth factor receptor kinase.

The 4-anilinoquinazoline PD 153035 (1) is a potential antitumor agent which acts by inhibiting tyrosine kinase activity of epidermal growth factor receptor (EFGR) via competitive binding at the ATP site of enzyme. A series of cyclic analogues of PD 153035 bearing the 1,4-dioxane ring was prepared by reaction of 6-chloro derivative 5 with several aniline nucleophiles. These were evaluated for their ability to inhibit the EGFR kinase and the growth of primary human tumor cell cultures. All of the new 4-anilinoquinazolines exhibited less potency than PD 153035 against EGFR kinase. However, compounds 2b, 2c, 2e, 2g, and 2h showed higher inhibitory activities than PD 153035 against the growth of A431 tumor cell line. The compound 2b containing 3-chloroaniline ring was as potent as PD 153035 against EGFR kinase and showed about 5.4-fold better potency than PD153035 in the inhibition of growth of A431 cell line with good selectivity.

Antineoplastic Agents↗
PubMed2005

Interactions between brushlike polyacrylic acid side chains on a polyacrylate backbone in dioxane-water.

Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert-butyl acrylate) macromonomer [M-P(tert-BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert-BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert-BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase.

Acrylic Resins↗
PubMed2002

Macroporous poly(L-lactide) scaffold 1. Preparation of a macroporous scaffold by liquid--liquid phase separation of a PLLA--dioxane--water system.

A biodegradable poly(L-lactic acid) (PLLA) macroporous scaffold with a regular and highly interconnected structure in the size range from 50 to 150 mu m was fabricated from a PLLA--dioxane--water ternary system with the use of the thermally induced phase separation (TIPS) process. The phase diagram of PLLA with molecular weight above 200,000 was measured. It was found that a small change in the water content in the solvent caused a large shift in the cloud-point temperature. The porous morphology of the scaffold was closely related to the quenching route and formulation parameters, including polymer concentration, quenching temperature, aging time, and solvent composition of the ternary system. The porous morphology development in the scaffold was recorded as a function of aging time by scanning electronic microscopy (SEM). For systems with lower polymer concentrations (<4.5 wt%), polymer sedimentation occurred in the later stages of phase separation. A slight increase in the water content of the solvent mixture caused the sedimentation boundary to expand to higher polymer concentration. For systems with higher polymer concentrations (> or = 4.5 wt%), the development of phase separation was restricted by gelation that resulted from the crystallization of the PLLA chains. This gelation effect was greater at high polymer concentrations and low quenching temperatures. The macroporous expected scaffold could be optimized from the slow development of phase separation during the long coarsening process.

Absorbable Implants↗
PubMed1994

X-ray structural studies and physicochemical characterization of the 1-butanol, 1-pentanol, and 1,4-dioxane solvates of succinylsulfathiazole.

The crystal structures and thermal decomposition of three solvated forms of the antibacterial drug succinylsulfathiazole (SST) have been studied. The solvates, with 1:1 host-guest stoichiometry, are SST x 1-butanol (1) SST x 1-pentanol (2), and SST x 1,4-dioxane (3). Solvates 1 and 2 crystallize in the triclinic system, space group P1, with two formula units per cell, and are nearly isostructural. The OH groups of the guest molecules in both solvates engage in hydrogen bonding to the host SST and occupy cavities in the crystals. Solvate 3 is triclinic, space group P1, with two formula units per cell, but the two independent solvent molecules are located in crystallographically distinct channels. In one channel, solvent molecules are hydrogen bonded to the host while, in the other, they are held by van der Waals interactions only. The structural results are in accord with thermogravimetric and differential scanning calorimetric data which indicate one-step desolvation for 1 and 2 but two-step desolvation for 3. X-ray powder diffraction was used to attempt identification of the polymorphic forms of SST resulting from desolvation of 1-3. Desolvation of 1 and 3 appears to yield pure polymorphs of SST while 2 yields a mixture of polymorphs. The activation energies for the desolvation of the nearly isomorphous solvates 1 and 2 were found by dynamic thermogravimetry to be 155 and 149 kJ mol(-1), respectively.

1-Butanol↗
PubMed1981

Effects of dioxane on RNA synthesis in the rat liver.

The effect of dioxane on transcription was investigated. On intravenous administration of the lower dose (10 mg/rat) both RNA polymerase A and B activities were initially depressed but recovered after 1 h. A secondary effect on RNA polymerase A was observed but the enzyme activity recovered at 24 h when it was about 35% above control values whereas RNA polymerase B activity had achieved control values. With a higher dose (100 mg/rat) the pattern was similar but the suppressive effects were more pronounced - RNA polymerase B activity never attained control values during the times studied whereas there was no increase in RNA polymerase A activity at 24 h.

Animals↗
PubMed1976

Dielectric increment of low molecular weight RNA in dioxane after application of static electric fields.

A soluble RNA with a molecular weight between 15 000 and 23 000 was extracted from calf thymus and chromatographically purified. The RNA was slightly soluble in doxane (approx. 2.5 mug/ml) and RNA-dioxane solutions were used to fill a cell (452.02 pF capacitance) to which static electric fields of variable strength were applied. The dielectric permittivity of the solutions was measured at a fixed time interval after the application of the electric field. The RNA solutions showed a dielectric increment proportional to the strength of the applied field and to the RNA concentration. The existence of a hystersis effect was proven and the effect of the electric field on the RNA molecule might be related to a dielectric saturation phenomenon parallel to long-term changes of the molecule.

Animals↗
PubMed1981

Carcinogenicity and mutagenicity of solvents. I. Glycidyl ethers, dioxane, nitroalkanes, dimethylformamide and allyl derivatives.

The carcinogenicity and/or mutagenicity as well as structural features and relationships of the glycidylethers (principally phenyl-, butyl-, allyl-, and isopropyl-), dioxane, nitroalkanes (nitro methane, ethane and propane), dimethylformamide and allyl derivatives (chloride, alcohol and amine) were examined. Additionally, considerations of the production, use patterns, estimated populations at risk, TLV's and metabolism of the above agents were discussed.

Allyl Compounds↗
PubMed1988

The synthesis of a novel thromboxane receptor antagonist 4(Z)-6-(2-o-chlorophenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl) hexenoic acid ICI 192605.

The synthesis and summary pharmacology of a novel thromboxane receptor antagonist 4(Z)-6-(2-o-chlorophenyl-4-o-hydroxyphenyl-1, 3-dioxan-cis-5-yl) hexenoic acid (3) is reported. Compound 3 was competitive and selective with pA2 values of 8.0 +/- 0.1 (rabbit) and 8.4 +/- 0.05 (rat) on smooth muscle preparations and 8.16 +/- 0.01 on human platelets. In vivo activity of 3 was demonstrated in a Konzett Rossler guinea pig model at 0.01 mg/kg p.o.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗