Chromatographic investigations of the photolysis products of nitrobenzenes

Summary By using gas, liquid, column and thin-layer chromatography and spectroscopy the main products of the photolysis of nitrobenzene in ethereal solutions have been identified. These are: azobenzene, azoxybenzene, nitroazoxybenzene, 4-aminoazobenzene, 3- and 4-nitrobenzene, 2-, 3- and 4-nitrophenol, 1,4-quinone, phenol, aniline and 4-nitroaniline. The photolysis was carried out by irradiation with a mercury lamp. The removal of oxygen from the irradiated solution was found to affect both the qualitative and quantitative composition of the photolysis products. The mechanism of the photochemical processes occurring in the irradiated nitrobenzene solutions is discussed.     

Anion-exchange behaviour of a number of metal ions on DEAE-cellulose in hydrobromic and hydriodic acid media

Summary The adsorption behaviour of 48 metal ions on DEAE-cellulose layers has been investigated in aqueous hydrobromic and hydriodic acid media. R_F values are given as a function of the hydrobromic and hydriodic acid concentration over the ranges 0.01–6 mol dm^–3 and 0.01–3 mol dm^–3, respectively, and are compared with those obtained with Avicel SF. R_F spectra are comparatively simple in both media, reflecting the strong affinity of the bromide and iodide ions to the DEAE-cellulose phase. Pd, Pt, Re, Au and Hg are distributed chromatographically in either system, while most other metal ions exhibit rather extreme R_F values of near unity or zero. Therefore, the selectivity of the systems is particularly high for Pd, Pt, Re, Au and Hg, providing the possibility of their excellent selective separations.     

Highly selective reduction of nitrobenzenes to azoxybenzenes with a copper catalyst

A convenient protocol for highly selective delivery of azoxybenzenes from reduction of nitrobenzenes was developed by utilizing a copper catalyst. A variety of functional groups and substitution were well tolerated.     

New deconjugation reaction of (E)-1-indanylidene methylarene brought by photolysis with protic acid

A new photodeconjugation reaction of (E) indanylidene methylarenes (1a-d) carried out by photolysis in the presence of protic acid are reported with 80% to >95% yields. The reaction mechanism is through the protonation of the less stable (Z) isomer to form stable indanyl cation followed by deprotonation.     

One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation

We demonstrated how a reduction step with a reducing system comprised of In(OTf)₃ and Et₃SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.     

A Unique Photoreaction of Hypericinate Bound to Human Serum Albumin,Lipids, or Vesicles

Summary. Hypericinate bound to human serum albumin is effectively photo-bleached. This reaction occurs to a lesser extent for hypericinate incorporated into dipalmitoyl-phosphatidyl-cholin vesicles or lecithin. Surprisingly, the photo-bleaching was strongly retarded for the complex of hypericinate with bovine serum albumin. In homogeneous solutions in a variety of solvents, micellar systems, and in ethanolic solutions containing additives mimicking possibly active parts of the mentioned hosts, almost no photoreaction was discernible. No products besides hypericin could be recovered from a bleached system. It was concluded that the main photoreaction involves photo-reduction or photo-addition in which the product becomes specifically stabilized by the host, but reverts partly to hypericinate upon destruction of the complex.Received June 23, 2003; accepted July 1, 2003 Published online September 11, 2003     

Simple synthesis of fresh alkyl iodides using alcohols and hydriodic acid

A simple synthesis of fresh alkyl iodides using alcohols and hydriodic acid (HI) is reported. The alkyl iodides were obtained in quick and easy work-up with good to excellent yields (66-94%) and very high purities (97-99%). Freshly prepared iodomethane and 1-iodobutane were applied to synthesize biologically relevant 3,7-dimethyladenine and 9-butyladenine, which were characterized thoroughly using 1D and 2D NMR, individually.     

Microflow photochemistry—a reactor comparison study using the photochemical synthesis of terebic acid as a model reaction

The continuous-microflow photochemical synthesis of terebic acid from maleic acid was investigated in two different microreactor set-ups. The results were subsequently compared to analogue experiments in a conventional chamber reactor. Based on conversion rates, reactor design and energy efficiency calculations, the simple microcapillary reactor showed the best overall performance.     

Photochemistry of N-Phenylbenzenecarbohydroxamic acid

N-Phenylbenzenecarbohydroxamic acid undergoes a photoreaction in cyclohexane and methanol to give benzanilide as a major product.

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Photochemie von N-Phenylbenzolcarbohydroxamsäure

Zusammenfassung N-Phenylbenzolcarbohydroxamsäure ergibt in einer Photoreaktion (in Cyclohexan und Methanol) Benzanilid als Hauptprodukt.

     

Hydrochlorofluoromethylation of unactivated alkenes with chlorofluoroacetic acid

An operationally simple method enabling hydrochlorofluoromethylation of unactivated alkenes under visible light activation is reported. The procedure has various benefits. It uses commercially available and inexpensive chlorofluoroacetic acid and phenyliodine(III) diacetate for the generation of the required chlorofluoromethyl radical, it converts feedstock olefins into attractive 1-chloro-1-fluoroalkanes, and it tolerates a broad variety of functional groups. The chlorofluoromethyl radical has a reactivity profile towards alkenes similar to the nucleophilic difluoromethyl radical.     

Reaction of S-allyl and propargyl derivatives of 2-thiouracils with hydrobromic acid

Hydrobromic acid reacts with 2-methallylthio- and 2-prenylthio-4(3Н)-pyrimidinones with participation of the double bond to give the products of heterocyclization, and with 2-allylthio- and 2-propargylthio-6-methyl-4(3Н)-pyrimidinones, with the retention of the double bond and the formation of hydrobromides.     

Extraction of certain elements from hydrobromic and perchloric acid

Zusammenfassung Die Extraktion von Pa, Fe, Hg, Ag, Zn, Co und Se aus Bromwasserstoffund Perchlorsäurelösungen mit Trilaurylamin oder Tributylphosphat wurde in Abhängigkeit von der Säurekonzentration in der wäßrigen Phase und der Lösungsmittelkonzentration in der organischen Phase untersucht. Der Extraktionsvorgang wurde an Hand der Ergebnisse diskutiert. Ebenso wurden die besten Bedingungen für die Trennung der genannten Metallionen ermittelt.     

Reaction of Aromatic and Unsaturated Compounds with the Potassium Permanganate/HCl (HBr) Acetonitrile Reagent

Addition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the corresponding vicinal dihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25-60 °C) with excellent to moderate yields.     

Synergistic effect of UV and l-ascorbic acid on the reduction of graphene oxide: Reduction kinetics and quantum chemical simulations

A photochemical strategy for eco-friendly reduction of graphene oxide (GO) was developed by using l-ascorbic acid (L-AA) as a photosensitive reducing agent. L-AA was excited and oxidized with deprotonation by UV irradiation (254 nm) and the proton coupled electron transfer induces chemical reduction of GO. This photochemical process is quite eco-friendly and scalable, and the reduction kinetics and degree of GO were highly enhanced. To understand the improved reduction power by UV light, the redox properties of L-AA in the ground and excited states were characterized by using quantum chemical simulations. Based on the results, we clearly demonstrated the mechanism how UV irradiation considerably enhances the reducing power of L-AA for the reduction of GO.     

Ionic dissociation of aqueous hydrobromic acid. V. Estimate from refractive index and density measurements

The refractive index of aqueous hydrobromic acid was measured up to 19.6m at 0.25 and 60°C. The density of dilute solutions, 0.0676 to 2.76m, was measured at 25°C to high accuracy. These and supplementary data from the literature yielded apparent molar volumes and refractivities. The latter showed the shallow maximum at low concentrations (less than 1.5m) and the gentle linear decline with increasing concentrations, characteristic of strong electrolytes up to about 8 m. The abrupt decline of the apparent molar refractivity with increasing concentrations is interpreted in terms of the association of hydrobromic acid. The apparent molar volumes can also be interpreted, though only quantitatively, in these terms. The results are related to the previously obtained proton nmr data, concerning the extent of association.     

Mechanistic study of the oxidation of -ascorbic acid by chloranil at the nitrobenzene water interface

The redox reaction between -ascorbic acid in water and chloranil in nitrobenzene has been studied by means of polarography with an ascending water electrode as well as cyclic voltammetry with a stationary interface. Through accurate measurement of the limiting currents, it has been suggested that the redox reaction should be a two-electron reaction rather than a one-electron reaction described previously. A spectrophotometric technique has also been used to observe that the redox reaction proceeds spontaneously under certain conditions even without electrochemical control. Based on these findings, it has been concluded that the present heterogeneous charge transfer reaction is the ion transfer of chloranil semiquinone radical, which is driven by the homogeneous electron transfer between ascorbic acid and chloranil in the aqueous phase.     

Radiochemical separation of selenium from hydrochloric or hydrobromic acid into toluene

A separation of selenium based on the extraction of different concentrations of Se(IV) from 12 M hydrochloric acid or 8 M hydrobromic acid into toluene is described. Recoveries of 92% and 97%, respectively, are achieved in 7 min. Oxidizing agents interfere.