- Strong Inhibition of Cis-Trans Isomerization of Azo Compounds by Hydroxide Ion
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The thermal cis-trans isomerization rate of methyl yellow (1), p-phenyl red (2), and o-methyl red (3) in aqueous solution was measured at different hydroxide ion concentrations, and it was found that there is a very strong inhibition as the pH increases.For 1 the rate changes from 2.17*10-2 s-1 at NaOH 6*10-3 M to 1.0*10-3 s-1 at NaOH 0.1 M.The observed rate constant for 2 was too fast for the experimental technique used at a concentration of NaOH lower than 0.01 M.These results are interpreted in terms of a much faster rate of isomerization of the protonated cis compounds than the neutral ones, and values for the pKa and rate constants for both species are calculated.
- Sanchez, Ana,Rossi, Rita H. de
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Read Online
- Photochromic behavior in the molecular glass of 4,4′,4″-tris(3-methylphenyphenylamino)triphenylamine
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For the purpose of gaining information on the microstructure of molecular glasses, photochromic behavior of 4-dimethyl-aminoazobenzene (DAAB) in the molecular glass of 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA) was studied in comparison with that in a polystyrene matrix and in a benzene solution. The results strongly suggest that the local free volume in the molecular glass of m-MTDATA is smaller than that in the polystyrene glass.
- Nakano, Hideyuki,Akamatsu, Keiichi,Moriwaki, Kazuyuki,Shirota, Yasuhiko
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Read Online
- Photochromic reaction in a molecular glass as a novel host matrix: The 4-dimethylaminoazobenzene-4,4′,4″-tris [3-methylphenyl(phenyl)amino]triphenylamine system
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For the purposes of clarifying the properties of a molecular glass as a novel host matrix and gaining information on the microstructure of the molecular glass, the photochromic behavior of 4-dimethylaminoazobenzene (DAAB) in a novel molecular glass of 4,4′,4″-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) was investigated, and compared with its behavior in a polystyrene glass matrix and a benzene solution. It was found that the fraction of the photoisomerized cis-isomer of DAAB at the photostationary state is smaller in the m-MTDATA glass matrix than in the polystyrene matrix and the benzene solution, and that the apparent initial rate constant for the backward cis→trans thermal isomerization of DAAB is much larger in the m-MTDATA glass than in the polystyrene matrix and the benzene solution. These results suggest that the average size of local free volume in the molecular glass of m-MTDATA is smaller than that in the polystyrene glass.
- Moriwaki, Kazuyuki,Kusumoto, Mitsushi,Akamatsu, Keiichi,Nakano, Hideyuki,Shirota, Yasuhiko
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Read Online
- Calculated oxidation potentials predict reactivity in Baeyer-Mills reactions
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Azobenzenes are widely used as dyes and photochromic compounds, with the Baeyer-Mills reaction serving as the most common method for their preparation. This transformation is often plagued by low yields due to the formation of undesired azoxybenzene. Here, we explore electronic effects dictating the formation of the azoxybenzene side-product. Using calculated oxidation potentials, we were able to predict reaction outcomes and improve reaction efficiency simply by modulating the oxidation potential of the arylamine component.
- Gingrich, Phillip W.,Olson, David E.,Tantillo, Dean J.,Tombari, Robert J.,Tuck, Jeremy R.,Yardeny, Noah
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supporting information
p. 7575 - 7580
(2021/09/22)
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- Manganese Catalyzed Hydrogenation of Azo (N=N) Bonds to Amines
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We report the first example of homogeneously catalyzed hydrogenation of the N=N bond of azo compounds using a complex of an earth-abundant-metal. The hydrogenation reaction is catalyzed by a manganese pincer complex, proceeds under mild conditions, and yields amines, which makes this methodology a sustainable alternative route for the conversion of azo compounds. A plausible mechanism involving metal-ligand cooperation and hydrazine intermediacy is proposed based on mechanistic studies. (Figure presented.).
- Ben-David, Yehoshoa,Das, Uttam Kumar,Diskin-Posner, Yael,Kar, Sayan,Milstein, David
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p. 3744 - 3749
(2021/07/09)
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- Trichloroisocyanuric Acid Mediated Oxidative Dehydrogenation of Hydrazines: A Practical Chemical Oxidation to Access Azo Compounds
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A highly efficient, metal-free, chemical oxidation of hydrazines has been implemented using environmentally friendly TCCA as oxidant. This benign protocol provides straightforward access to a wide range of azo compounds in THF in excellent yield. Altogether, 35 azo compounds were obtained in this way and scale-up preparations were performed. Additionally, a plausible mechanism was also proposed. Step-economical process, mild reaction conditions, operational simplicity, high reaction efficiency, and easy scale-up highlight the practicality of this methodology.
- Cao, Guiyan,Hu, Yulai,Huang, Danfeng,Huo, Congde,Liu, Xuan,Su, Yingpeng,Wang, Ke-Hu,Yu, Jie,Zhang, Rong,Zhao, Yanan
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supporting information
p. 1103 - 1112
(2020/04/01)
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- Method for preparing asymmetric azobenzene and azobenzene oxide compounds through photocatalysis
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The invention relates to a method for preparing asymmetric azobenzene and azobenzene oxide compounds through photocatalysis. Through a photocatalyst, an aromatic nitro compound reacts with an aromaticamino compound under the conditions of illumination and inert gas to obtain an asymmetric azobenzene compound represented by a formula I and an asymmetric azoxybenzene compound represented by a formula II; the method can be used for replacing a conventional mature organic synthesis process, has the advantages of mild conditions, high selectivity and universality, and is suitable for industrial production.
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Paragraph 0028-0030; 0059; 0060
(2020/02/27)
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- Hole Catalysis as a General Mechanism for Efficient and Wavelength-Independent Z → E Azobenzene Isomerization
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Whereas the reversible reduction of azobenzenes has been known for decades, their oxidation is destructive and as a result has been notoriously overlooked. Here, we show that a chain reaction leading to quantitative Z → E isomerization can be initiated before reaching the destructive anodic peak potential. This hole-catalyzed pathway is accessible to all azobenzenes, without exception, and offers tremendous advantages over the recently reported reductive, radical-anionic pathway because it allows for convenient chemical initiation without the need for electrochemical setups and in the presence of air. In addition, catalytic amounts of metal-free sensitizers, such as methylene blue, can be used as excited-state electron acceptors, enabling a shift of the excitation wavelength to the far red of the azobenzene absorption (up to 660 nm) and providing quantum yields exceeding unity (up to 200%). Our approach will boost the efficiency and sensitivity of optically dense liquid-crystalline and solid photoswitchable materials. Video Abstract: [Figure presented] Molecular switches are a key ingredient in stimulus-responsive and adaptive materials and devices. Light is among the most attractive stimuli, yet photoswitches often require intense irradiation with high-energy UV light and suffer from inefficient switching as well as fatigue. Thus, the design of robust and efficient photoswitches constitutes an important challenge to boost the sensitivity and energy efficiency of the respective materials and devices. Here, we describe that the isomerization of azobenzene switches from their less stable Z isomer back to the more stable E isomer can be triggered by tiny, i.e., catalytic, amounts of holes caused by chemical, electrochemical, or photochemical oxidation. Our method is generally applicable to the entire family of azobenzene switches, does not require expensive equipment, and allows the reliable and efficient operation of these photoswitches by using red light with quantum efficiencies up to 200%. An efficient and generally applicable method is developed for operating azobenzene molecular switches by using catalytic amounts of holes (via an oxidant) or photons (via a photosensitizer). The pathway allows for indirect Z → E photoisomerization using lower-energy light than required for direct azobenzene excitation and with high quantum yields exceeding unity. The method should help to enhance the sensitivity of photoresponsive materials and devices with high optical density.
- Goulet-Hanssens, Alexis,Rietze, Clemens,Titov, Evgenii,Abdullahu, Leonora,Grubert, Lutz,Saalfrank, Peter,Hecht, Stefan
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supporting information
p. 1740 - 1755
(2018/06/29)
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- Method for highly stereoselective preparation of trans-aromatic tertiary amine azo compound
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The invention provides a method for efficient and highly stereoselective preparation of an azo compound through para C-H bond selective activity of an organic aromatic tertiary amine. According to themethod, a Bronsted acid is adopted as a catalyst, an aromatic diazonium tetrafluoroboric acid compound and an organic aromatic tertiary amine compound are adopted as reaction substrates, and an organic solvent is put into a reaction system. The method has the advantages that the catalyst is cheap and easy to obtain, high in substrate applicability, gentle in reaction condition and safe and reliable; the selectivity of a target product is approximate to 100%, the E/Z selectivity of the target product is greater than 99:1, and relatively high yield is achieved; and by adopting the method, the defects that a conventional method for synthesizing different aromatic functional groups to replace organic aromatic tertiary amine azo compounds is harsh in reaction condition, poor in reaction selectivity, tedious in experiment step, low in yield, harmful to the environment since reagents harmful to the environment are used, and the like, can be overcome, and good industrial application prospectscan be achieved. The invention further provides an organic aromatic tertiary amine azo compound with different aryl substituted functional groups.
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Paragraph 0015; 0016; 0017
(2018/07/30)
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- Azo disperse dyes and sublimation transferring ink comprising thereof
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The present invention relates to a sublimation transfer ink which is used in digital textile printing (DTP). The present invention provides an azo-based disperse dye represented by chemical formula 1 and a sublimation transfer ink comprising the azo-based disperse dye. In chemical formula 1, R_1 and R_2 are each independently an alkyl group having 6 to 8 carbon atoms, R_3 is each independently H, NO_2 or SCO_2H_3, R_4 and R_5 are each independently H, NO_2, Cl or CN, R_6 is each independently H or NHCO_2CH_3, and R_7 is each independently H, CH_3, OCH_3, or OCH_2CH_3. The azo-based disperse dye and the transfer ink comprising the azo-based disperse dye can be used as a transfer ink specified to DTP since the azo-based disperse dye and the transfer ink comprising the azo-based disperse dye are not only excellent in transfer efficiency for fabrics such as a polyester fabric and the like, but also very excellent in washing fastness and light fastness.COPYRIGHT KIPO 2018
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Paragraph 0080; 0082; 0103-0106
(2018/08/19)
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- Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2
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The synthesis of azobenzenes has been a long-standing challenge. Their current preparation at a preparative or industrial scale requires stoichiometric amounts of environmentally unfriendly reactants. Herein, we demonstrate that the catalytic use of electrogenerated samarium diiodide (SmI2) could promote, in one-step synthesis, the reduction of nitrobenzenes into azobenzenes in high yields under mild reaction conditions. This catalytic procedure contains many elements satisfying a sustainable chemical process for the preparation of one of the most widely wanted family of chemical compounds. The easy synthetic procedure, and the absence of precious metals, bases, and nonhazardous substances, already makes our catalytic procedure a serious alternative to currently available methods. This is a promising method for the efficient synthesis of both symmetrical and asymmetrical azo compounds with a high functional group tolerance.
- Zhang, Yu-Feng,Mellah, Mohamed
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p. 8480 - 8486
(2017/12/08)
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- Mesoporous manganese oxide catalyzed aerobic oxidative coupling of anilines to aromatic azo compounds
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Herein we introduce an environmentally friendly approach to the synthesis of symmetrical and asymmetrical aromatic azo compounds by using air as the sole oxidant under mild reaction conditions in the presence of cost-effective and reusable mesoporous manganese oxide materials.
- Dutta, Biswanath,Biswas, Sourav,Sharma, Vinit,Savage, Nancy Ortins,Alpay, S. Pamir,Suib, Steven L.
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supporting information
p. 2171 - 2175
(2016/02/18)
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- Convenient and rapid diazotization and diazo coupling reaction via aryl diazonium nanomagnetic sulfate under solvent-free conditions at room temperature
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For the first time, nanomagnetic-supported sulfonic acid is used for conversion of several types of aromatic amine, containing electron-withdrawing groups as well as electron-donating groups to the corresponding azo dyes in excellent yield. The synthesis of these compounds is described by the sequential diazotization-diazo coupling of various aromatic amines with sodium nitrite, nanomagnetic supported sulfonic acid and coupling agents under solvent-free conditions at room temperature. This new method offers several advantages including short reaction time, mild reaction conditions, avoidance of harmful acids, and simple work-up procedure. More importantly, aryldiazonium salts supported on magnetic nanoparticles (aryl diazonium nanomagnetic sulfate) were sufficiently stable to be kept at room temperature in the dry state.
- Koukabi, Nadiya,Otokesh, Somayeh,Kolvari, Eskandar,Amoozadeh, Ali
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- Nano-CuFe2O4-supported sulfonic acid as a novel and recyclable nanomagnetic acid for diazotization of aromatic amines: efficient synthesis of various azo dyes
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Abstract: A novel heterogeneous sulfonic acid functionalized nanomagnetic CuFe2O4 was successfully prepared and characterized by analyzing different obtained data including Fourier transform infrared spectroscopy, X-ray powder diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, dynamic light scattering and vibrating sample magnetometer. Then the novel acidic reagent was examined in synthesis of various azo-containing compounds from coupling of aryl diazonium ferrite sulfate salts with aromatic and non-aromatic compounds. The procedure starts by diazotization of aromatic amines with NaNO2 and wet CuFe2O4–SO3H and then coupling reaction of aryl diazonium ferrite sulfate salts with appropriate reagent. The prepared nano-solid acid showed high activity in synthesis of variety of aryl diazonium salts. In addition the as-prepared aryl diazonium ferrite sulfate salts are stable at room temperature for many hours and reacted efficiently in coupling reactions of aryl diazonium salts. All the azo dyes are synthesized in high yields and simple reaction conditions at room temperature. Moreover, the nanomagnetic solid acid was easily recovered from the reaction mixture and reused five runs without significant loss of activity. Graphical Abstract: [Figure not available: see fulltext.]
- Nemati, Firouzeh,Elhampour, Ali,Natanzi, Mahshid B.,Sabaqian, Samaneh
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p. 1045 - 1054
(2016/05/02)
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- Monoazo dye whose color changes when an acid is added
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The present invention relates to a monoazo dye for detecting acid, which changes its color by adding acid or being exposed to acid and, more specifically a monoazo dye for detecting acid, which changes its color within seconds when being exposed to a small amount of strong acid and fiber products using the same wherein the monoazo dye for detecting acid can change its color in response to a small amount of strong acid and turns its color back by removing acid, and fiber dyed by using the monoazo dye has a high color fastness and accordingly has no discoloration due to laundry and sunlight. Therefore, a protective clothing using the fiber let workers know when they are exposed to acid or not on a real time basis and accordingly prevents a secondary big accident and another accident causing by harmful environment factors in accident sites.(AA) Acid adsorption(BB) Acid removalCOPYRIGHT KIPO 2015
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Paragraph 0046-0052; 0099-0102
(2016/10/10)
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- Carboxyl and nitrite functionalized graphene quantum dots as a highly active reagent and catalyst for rapid diazotization reaction and synthesis of azo-dyes under solvent-free conditions
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Carboxyl and nitrite functionalized graphene quantum dots was prepared from carboxyl and hydroxyl functionalized graphene quantum dots using NaNO2 in the absence of mineral acids. This functional group conversion was confirmed by FT-IR spectroscopy, photoluminescence and X-ray diffraction. The carboxyl and nitrite functionalized graphene quantum dots was used as an effective nitrosonium ion source and reusable catalyst for the efficient diazotization of a variety of arylamines without using any additional acid. Subsequent azo-coupling of these freshly prepared diazonium salts with a range of active aromatic compounds led to the requisite azo-dyes in excellent yields in very short reaction times with a simple experimental procedure.
- Valizadeh, Hassan,Shomali, Ashkan,Nourshargh, Saideh,Mohammad-Rezaei, Rahim
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p. 522 - 528
(2015/03/18)
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- Synthesis of a nitrite functionalized star-like poly ionic compound as a highly efficient nitrosonium source and catalyst for the diazotization of anilines and subsequent facile synthesis of azo dyes under solvent-free conditions
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Nitrite functionalized star-like poly ionic (NFSPI) compound was synthesized and used as a highly efficient nitrosonium source and catalyst for the conversion of aniline derivatives to diazonium salts. Azo dyes were prepared via in situ azo-coupling reaction of these diazoniums with active aromatic compounds under solvent-free conditions in very short reaction time in excellent yields. NFSPI plays dual role as a three-dimensional nitrosonium source and catalyst because of its poly ionic characteristic. The isolated products were confirmed with FT-IR spectrum, 1H-NMR, 13C-NMR spectroscopy and CHNSO analysis. The structure of heterogeneous reagent and catalyst was confirmed by FT-IR spectrum, SEM images, EDX and CHNSO analysis. Yields and reaction times for the synthesis of a variety of products via this procedure were compared with reported values in literature.
- Valizadeh, Hassan,Shomali, Ashkan,Ghorbani, Jalal,Noorshargh, Saeideh
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- Microwave synthesis of a photocatalytically active SnO-based material
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Tin(II) oxide nanopowder has been prepared through microwave processing of an ammoniacal Sn6O4(OH)4 suspension, and the effect of synthesis duration on the surface morphology, acid-base properties, and photocatalytic activity of the SnO has been examined. The results demonstrate that the surface morphology plays a key role in determining the photocatalytic activity of powder SnO for methyl orange photo-degradation.
- Kuznetsova,Pichugina,Kozik
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p. 387 - 391
(2014/04/17)
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- A new nitrite ionic liquid (IL-ONO) as a nitrosonium source for the efficient diazotization of aniline derivatives and in-situ synthesis of azo dyes
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A new task-specific nitrite containing ionic liquid derived from the O-nitrosation of N-methyl-N-hydroxybutylimidazolinium chloride was synthesized and used as a source of nitrosonium ion to affect the efficient diazotization of arylamines. The diazonium salts thus obtained were coupled, using standard experimental procedures, to a range of tertiary anilines, phenols and naphthols to afford the requisite azo dyes in good yield. The diazotization and subsequent azo-coupling generated the related azo dyes at 0-5 °C in short reaction times with a simple experimental procedure.
- Valizadeh, Hassan,Shomali, Ashkan
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experimental part
p. 1138 - 1143
(2012/03/27)
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- Azo compounds reducing formation and toxicity of amyloid beta aggregation intermediates
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The present invention relates to compounds suitable as modulators of protein misfolding and/or protein aggregation. The compounds are particularly suitable as inhibitors of amyloid aggregate formation and/or modulators of amyloid surface properties, and/or as activators of degradation or reduction of amyloid aggregates.
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- Ionic liquid 1-(3-trimethoxysilylpropyl)-3-methylimidazolium nitrite as a new reagent for the efficient diazotization of aniline derivatives and in situ synthesis of azo dyes
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A new ionic liquid 1-(3-trimethoxysilylpropyl)-3-methylimidazolium nitrite was synthesized. This ionic liquid was used as a convenient nitrosonium source in diazotization of arylamines into their corresponding diazonium salts which were converted into their related azo dyes via the in situ azo-coupling with aniline derivatives or phenolic compounds. The diazotization of anilines in this ionic liquid and subsequent azo-coupling generated the related azo dyes in good to excellent yields at 0-5 °C in short reaction times via a simple experimental procedure.
- Valizadeh,Amiri,Shomali,Hosseinzadeh
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experimental part
p. 495 - 501
(2012/07/13)
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- Modified clays as efficient acid-base catalyst systems for diazotization and diazocoupling reactions
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Diazotization and diazocoupling reactions of aniline and its substituted derivatives with phenol and other aromatic amines over ecofriendly clay catalysts is described. This inexpensive, non-corrosive and reusable catalysts were found to exhibit bifunctional catalytic properties for these reactions. No considerable decrease in the efficiency of the catalysts were observed after five cycles of operation. The new method totally avoids the use of acids and alkalies.
- Bahulayan, Damodaran,John, Litka,Lalithambika, Malathy
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p. 863 - 869
(2007/10/03)
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- Complexation of 4-Dimethylaminoazobenzene with Various Kinds of Cyclodextrins: Effects of Cyclodextrins on the Thermal cis-to-trans Isomerization
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On the basis of the change in electronic and induced circular dichroism spectra for complex formation, the complexation of 4-dimethylaminoazobenzene (DAAB) with four kinds of cyclodextrins (α- and β-cyclodextrin (CD), heptakis(2,6-di-O-methyl)-β-cyclodextrin, and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin) was studied in methanol-water and dimethyl sulfoxide-water mixtures. It was found that the trans and cis isomers of DAAB form two different types of complex (inclusion and lid type) with CDs, depending on the kinds of CDs and solvents. Further, we have examined the effect of CDs on the thermal cis-to-trans isomerization of DAAB. The accelerated or decelerated effect on the thermal isomerization was observed upon adding CDs. The effects of CDs on the thermal isomerization are discussed in connection with the complexation of the cis-isomer of DAAB with CDs.
- Sueishi, Yoshimi,Hishikawa, Hiroaki
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p. 481 - 487
(2007/10/03)
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- A mild dehydrazination reaction of arylhydrazines using nitric oxide in the presence of oxygen
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A new dehydrazination reaction of arylhydrazines using nitric oxide and oxygen as a mild nitrosating agent is described. Taking advantage of non-aqueous and non-acidic medium appears to cause this novel selectivity as a counterpart of the azide synthesis by the conventional methods. The generally and reaction mechanism were also investigated.
- Matsuya, Yuji,Itoh, Takashi,Nagata, Kazuhiro,Ohsawa, Akio
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p. 15701 - 15710
(2007/10/03)
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- Reaction of Nitric Oxide with Amines
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Reactions of nitric oxide (NO) with amines in organic solvents were studied using Hantzsch dihydropyridines and aromatic primary amines as substrates. Hantzsch dihydropyridines are readily oxidized by nitric oxide to give the corresponding pyridines in quantitative yields. The addition of oxygen accelerates the reaction rate considerably. On the other hand, aromatic primary amines give deaminated products by the reaction with nitric oxide only in the presence of oxygen in ethereal solvents or chloroform.
- Itoh, Takashi,Nagata, Kazuhiro,Matsuya, Yuji,Miyazaki, Michiko,Ohsawa, Akio
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p. 3582 - 3585
(2007/10/03)
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- Reductive deamination of aromatic amines with nitric oxide (NO)
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Aromatic amines were treated with nitric oxide in tetrahydrofuran or chloroform under argon atmosphere to afford deaminated aromatic compounds in good yields. The reaction is suggested to proceed via aryl radicals, which are supposed to be formed by reduction of aryldiazonium salts with NO.
- Itoh, Takashi,Matsuya, Yuji,Nagata, Kazuhiro,Ohsawa, Akio
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p. 4165 - 4168
(2007/10/03)
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- Effect of β-cyclodextrin on the thermal Cis-trans isomerization of azobenzenes
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The cis-trans thermal isomerization of p-methyl red (1), o-methyl red (2), and methyl orange (3) was inhibited by β-cyclodextrin (β-CD) at constant pH. Their isomerization rate decreased 4, 8, and 1.67 times, respectively, in a solution containing 0.01 M β-CD. This effect can be attributed to the formation of an inclusion complex between the substrate and β-CD which hinders the rotation of the N=N bond. The isomerization rate of methyl yellow (4), 4-(dimethylamino)-4′-methoxy-azobenzene (5), and naphthalene-1-azo[4′-(dimethylamino)benzene] (6) was not affected by β-CD due to the presence of an organic cosolvent in the solution which displaces the azobenzene from the cavity, and the complex formed is probably equatorial. In addition, the transition state for the isomerization of compounds 1-3 involves rotation and that of 4-6, which have only electron-donating groups, inversion. This latter process brings about less volume change than rotation so it is less hindered by the complexation with β-CD.
- Sanchez, Ana M.,De Rossi, Rita H.
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p. 3446 - 3451
(2007/10/03)
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- Influence of Hexasulfonated Calixarenes on the Reactivities of Arenediazonium Ions in an Aqueous System
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The pKa of Phenol Blue shifted from 4.6 to 6.2 because of complexation of protonated Phenol Blue in the cavity of hexasulfonated calixarene with dodecyl substituents (2C12).The finding stimulated us to examine whether the analogs (2C) suppress the dediazoniation of arenediazonium ions in an aqueous system as crown ethers do in organic solvents.We have found that 2C can suppress the dediazoniation in an aqueous system where neither 18-crown-6 nor anionic micelles are effective.The magnitude of the inhibition effect was 4-5 fold.The reaction rate of the diazo coupling with N,N-dimethylaniline was significantly suppressed in the presence of 2C, suggesting that arenediazonium ions are deactivated through comlexation with 2C.The novel stabilization effects were explained by the strong anionic reaction field which neither 18-crown-6 nor anionic micelles have: that is, 2C has a peculiar architecture that six sulfonato groups are circularly arranged on the edge of the calixarene cavity.
- Shinkai, Seiji,Mori, Seiichi,Araki, Koji,Manabe, Osamu
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p. 3679 - 3686
(2007/10/02)
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- Studies on UV/VIS Absorption Spectra of Azo Dyes. XV. An Analysis of the Absorption Spectra of 4,4'-Diaminoazobenzenes
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In the visible absorption spectrum 4,4'-bis-diethylaminoazobenzene shows two absorption maxima (λmax = 426 nm and λmax = 477 nm) with high intensity.Quantum chemical calculations and examinations by peak separation of six 4-substituted azobenzenes and six 4'-substituted 4-diethylaminoazobenzenes (1a-k) indicate that the longest wavelenght band is due to a n-?* transition and the other band is due to a ?-?*-transition.This is verified using an inrement system for ?-?* absorption maxima.A linear relation is found between intensity ratios of the two bands and the HAMMETT-?-constants of the substituents.With increasing electron releasing tendency of the substituents the absorption intensity of the n-?*-band increases.
- Haessner, C.,Mustroph, H.
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p. 113 - 119
(2007/10/02)
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- The Reaction of Diazonium Ion Generated from α-Azohydroperoxide with Phenols. The Isolation and Reaction of Diazoether Intermediate
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The reaction of benzenediazonium ion generated from α-azohydroperoxide with 1-naphthol gave a diazoether which rearranged to 2- and 4-phenylazo-1-naphthols.
- Tezuka, Takahiro,Ando, Setsuo,Wada, Toshinori
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p. 1667 - 1670
(2007/10/02)
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- Photochemical Decomposition of 4-Arylazo- and 4-Arylazoxy-N,N-dialkylaniline N-Oxides
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The 4-aryl-N,N-dialkylaniline N-oxides (1a-c) decompose on u.v. irradiation in aprotic solvents, undergoing deoxygenation as well as intramolecular hydrogen abstraction, to give amides and dealkylated products.The latter process is more important for the diethyl derivative (1b) (photoCope elimination).Visible irradiation is ineffective.The 4-arylazoxy-N,N-dialkylaniline N-oxides (2a-d) undergo photochemical deoxygenation from the amino group (major process) as well as from the azo group.The mechanism of these photoprocesses is discussed in general and in relation to the possible involvement of these N-oxide derivatives in photofading of the related azo dyes.
- Albini, Angelo,Fasani, Elisa,Moroni, Micaela,Pietra, Silvio
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p. 1439 - 1444
(2007/10/02)
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- Anion-catalyzed Phase-transfer Catalysis. I. Application to Diazo-coupling Reactions
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Anion-catalyzed phase-transfer catalysis was evidenced in the diazo-coupling reactions of the arenediazonium ion with a range of diazophile components in liquid-liquid- and liquid-solid two-phase systems.The tetrakisborate ion was effective as an anionic catalyst to accelerate the reactions.Comparisons of the reaction rates in the two-phase system with those in solution systems indicated that the acceleration was due to the increased activity of the cationic reagent, partly by solubilization and partly by the dehydration of such cationic species in the nonpolar organic phase.
- Iwamoto, Hidetoshi,Yoshimura, Masaji,Sonoda, Takaaki,Kobayashi, Hiroshi
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p. 796 - 801
(2007/10/02)
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- Electrophilic ipso-Substitutions. Part 2. Reactions of 3-Substituted Indoles and 4-Substituted NN-Dimethylanilines with Arenediazonium Ions
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3-Substituted indoles and 4-substituted NN-dimethylanilines react with arenediazonium ions to form 3-arylazo-indoles and 4-arylazo-NN-dimethylanilines, respectively.The formation of the ?-complex intermediate was interpreted both as electrophilic ipso-attack and as coupling of two radicals deriving from an electron transfer process.Both mechanisms are discussed on the basis of the experimental evidence and on the substrate oxidation potentials.The leaving abilities of the substituents are discussed on the basis of the experimental results.
- Colonna, Martino,Greci, Lucedio,Poloni, Marino
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p. 455 - 460
(2007/10/02)
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- Isomerization of β-pinene in the Vapour Phase over Alumina Catalyst: Influence of Partial Pressure of Nitrogen and Pyridine
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The isomerization of β-pinene in the vapour phase over alumina catalyst has been studied in the presence of nitrogen and pyridine.The isomerization proceeds via two parallel paths, one giving bicyclic products such as α-pinene and camphene and the other giving rise to monocyclic menthadienes such as dipentene, terpinolene, α-terpinene and γ-terpinene.Nitrogen acts as a diluent while pyridine functions as a diluent and as a poison.As a result, it affects the formation of different products to different extent.The isomerization of β-pinene over alumina follows a second order kinetics.Based on the experimental facts a tentative mechanism, in terms of carbonium ion intermediates, has been proposed.
- Krishnasamy, V.,Ratansamy, P.
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p. 1151 - 1154
(2007/10/02)
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- TETRAKISBORATE AS THE FIRST EFFICIENT NEGATIVELY CHARGED PHASE TRANSFER CATALYST. KINETIC EVIDENCES
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Remarkable acceleration was observed by use of sodium tetrakisborate as a negatively charged phase transfer catalyst for diazonium ion in the azo coupling reactions of aryl diazonium tetrafluoroborate with a range of diazophile components in liquid-liquid- and liquid-solid two-phase systems.Kinetics of the reactions was examined to confirm the phase transfer catalysis.
- Kobayashi, Hiroshi,Sonoda, Takaaki,Iwamoto, Hidetoshi,Yoshimura, Masaji
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p. 579 - 580
(2007/10/02)
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- The Influence of Hydrogen Bonding on the cis-trans Isomerization of 4-Dimethylamino-Azobenzene
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The cis-trans isomerization of 4-dimethylamino-azobenzene has been investigated spectrophotometrically in benzene solutions in the presence of some carboxylic acids, phenol and i-propanol.It has been established that proton donors increase the rate of cis-trans reaction.The catalytic effect can be attributed to a hydrogen bridged interaction between the azo group and the proton donor.At lower concentrations the effect is proportional to the concentration of the proton donor and to its hydrogen bonding ability, which is, however, not the same as the acid dissociation constant commonly used for weak acids in aqueous media.At higher concentrations of the catalyst, the interactions are more complicated: the dimerization of the acids must have an important role in the rate increasing processes. - Keywords: Cis-trans isomerization / 4-Dimethylamino-azobenzene / Hydrogen bonding
- Buvari, A.,Redling, I.,Barcza, L.
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- Insecticide evaporator comprising a stabilizer
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Insecticide evaporator comprising at least one volatile phosphoric ester insecticide, an agent for stabilizing the said ester against decomposition by protonization and used in an amount of 0.2 to 20% based on the weight of phosphoric ester, characterized in that the stabilizing agent contains at least one compound selected from the compounds of the chemical class of 1,3-benzodioxoles and at least one diazene.
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- Evaporator system comprising a stabilized pesticidal phosphoric acid ester and method for stabilizing such ester enclosed in an evaporator
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An evaporator system adapted for emitting insect killing vapors of an insecticide therefrom and comprising a liquid or solid composition enclosed therein, said insecticide consisting in at least one volatile phosphoric acid ester which is stabilized by at least one diazene compound.
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