Surface fixation of poly(ethylene glycol)via photodimerization of cinnamate group

This article reports a new fixation method for hydrophilic layers on substrates. The method is based on the photochemistry of the cinnamate group, which is capable of intermolecular dimerization upon ultraviolet (UV) light irradiation. The method used was as follows. First, two photoreactive polymers were sequentially coated on a polymeric surface: a polycinnamate as an adhesive layer and a cinnamated poly(ethylene glycol) (PEG) as a hydrophilic layer. Subsequently the surface was exposed to UV light. No delamination occurred upon washing with water and methanol; the photoreactive PEG was chemically bonded onto the surface via the polycinnamate. The higher the molecular weight of PEG, the higher the wettability of the surface was formed. Minimal cell adhesion was observed on such a surface. The biomedical applications of the method are discussed. © 1993 John Wiley & Sons, Inc.     

Predictions of molecular geometries and electronic spectra of complex unsaturated molecules from MC-LCAO-MO method with particular reference to triplet-triplet transitions of naphthalene

An MC-LCAO-MO approach which has been proposed for open-shell systems of unsaturated hydrocarbons having degenerate MO's is applied to naphthalene, calculating its molecular geometry and electronic spectrum. The results are compared with those obtained by the usual semi-empirical SCF-CI method and with experiment. As for benzene, anthracene, phenanthrene and triphenylene, the bond lengths and the -electron energies in their ground states are calculated in the same manner. Most of the calculated bond lengths are in fairly good agreement with experiment. The total -electron energies of the ground states obtained by the MC-LCAO-MO and SCF-CI methods agree within about 0.01 eV when CI is included and within about 0.1 eV when CI is not invoked. It is found that the electronic spectrum of naphthalene obtained by the present method is in good agreement with that derived from the SCF-CI method and also explains most part of experiments. A detailed discussion is given on the calculated triplet-triplet absorption spectrum and its intensity distribution of naphthalene.     

Isomerization polymerization of 2-vinyl-1,3-dioxolane by α,α′-azobisisobutyronitrile or by γ-ray irradiation

2-Vinyl-1,3-dioxolane was polymerized by use of α,α′-azobisisobutyronitrile (AIBN) or by γ-ray irradiation. The polymer obtained was white amorphous powder which melted at ca. 70°C. and was soluble in chloroform, acetone, and p-dioxane. The infrared spectrum of the polymer indicated peaks at 1735 cm.^?1 characteristic of the carbonyl group, and at 1200–1000 cm.^?1 characteristic of the acetal group, while no absorption at 990 and 3100 cm.^?1 due to the vinyl group was observed. The spectra of the polymers obtained by AIBN and by γ-ray irradiation were essentially identical. The saponified product of the polymer was white powder and its reduced viscosity was a little larger than that of the original polymer. These results indicate that the polymer has no ester unit in the main chain. The results of gas chromatographic analysis of the saponified product of the polymer, indicate the presence of a small amount of ethyl alcohol. The results of the saponification showed that the ester content in the polymer varied from 7 to 25% depending upon the polymerization temperature. These results indicate that 2-vinyl-1,3-dioxolane polymerized by AIBN or by γ-irradiation with two modes of vinyl and hydrogen migration, yielding a copolymer having the unit structures      

Aza-pinacol rearrangement: acid-catalyzed rearrangement of aziridines to imines

A series of di-, tri-, and tetra-substituted N-tosylaziridines [N-(toluene-p-sulfonyl)aziridines] 1, prepared by aziridination of the corresponding alkenes with N-[(tolyl-p-sulfonyl)imino]phenyliodinane (TsN = IPh), was found to undergo a BF3-catalyzed rearrangement (aza-pinacol rearrangement) under mild conditions to give the corresponding N-tosylimines 2 generally in satisfactory yields.     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Anion-exchange resin modified with bismuthiol-II, as a new functional resin for the selective collection of selenium(IV)

A functional resin for the collection of selenium(IV) has been prepared simply by the conversion of a common ion-exchange resin with bismuthiol-II which has three functional properties, namely the capabilities of selective reaction with selenium(IV), ion-exchange reaction with ion-exchange resin and strong physical sorption to the ion-exchange resin matrix. The binding ratio of selenium(IV) to bismuthiol-II on the resin was confirmed to be 1:4. The reaction was represented as follows: 4RSH + H(2)SeO(3)--> R-S-Se-S-R + R-S-S-R + 3H(2)O. Highly selective sorption of selenium(IV) was achieved, based on the formation of stable selenotrisulphide on the resin. Selenium(IV) sorbed on bismuthiol-II resin was eluted effectively with 8-13M nitric acid or some thiols, such as cysteine and penicillamine. In the cases of thiols, the elution of selenium was found to be also based on the formation of selenotrisulphide, and the bismuthiol-II resin was regenerated. Satisfactory results were obtained when this resin was applied to the determination of selenium(IV) in river, estuarine or sea water samples.     

Induced circular dichroism spectra of the cyclodextrin complexes with 2-Thioxo-1,3-benzodithiole and 2-Selenoxo-1,3-benzodithiole

The induced circular dichroism (ICD) spectra of -cyclodextrin (-CD) complexes with 2-thioxo-1,3-benzodithiole and 2-selenoxo-1,3-benzodithiole have been measured. From the signs of the ICD spectra of both complexes, the polarization directions for the excited states have been investigated.     

Regiocontrolled Syntheses of 3- or 5-Fluorinated Pyrazoles from 2,2-Difluorovinyl Ketones(1)

2,2-Difluorovinyl ketones 1 react with monosubstituted hydrazines to afford 5-fluoropyrazoles in a regioselective manner via replacement of the fluorine by the substituted nitrogen of the hydrazines and dehydration between the carbonyl group of 1 and the NH(2) end. The reactions are successfully effected for both aliphatic and aromatic hydrazines in aqueous ethanol under neutral conditions and in THF under basic conditions with butyllithium, respectively. A similar ring-forming reaction of 1 with hydrazine monohydrate is induced by the addition of trifluoroacetic acid to give N-unsubstituted 3-fluoropyrazoles, which in turn react with alkyl and aryl halides in the presence of sodium hydride, leading to a regiocontrolled synthesis of 3-fluoropyrazoles.