On the involvement of diazonium ions in the photorearrangement of azoxybenzene

1977 ◽  
Vol 55 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Nigel J. Bunce
Keyword(s):  
Excited State ◽  
Light Intensity ◽  
Substrate Concentration ◽  
Product Distribution ◽  
Weak Base ◽  
Rearrangement Product ◽  
Azoxy Compounds ◽  
Diazonium Ions ◽  
Azoxy Compound ◽  
Diazonium Ion

Photolysis of aromatic azoxy compounds in non-basic solvents in the presence of 2-naphthol leads quite generally to azonaphthols in addition to the normal photorearrangement product. Free diazonium ions are implicated as the precursors of the azonaphthols, both the latter and the usual photorearrangement product being derived from the same excited state of the azoxy compound. Variation of the solvent, light intensity, substrate concentration, and percent reaction all cause changes in the product distribution. Such changes can be accommodated by postulating an intermediate which can either afford the normal rearrangement product by loss of a proton to a weak base, or expel a diazonium ion when no base is present.

scholarly journals INFLUENCE OF CHEMICAL STRUCTURE ON THE RATE OF AZO COUPLING AND ITS SIGNIFICANCE IN HISTOCHEMICAL METHODOLOGY

1959 ◽  
Vol 7 (1) ◽  
pp. 50-65 ◽  
Author(s):  
MARVIN M. NACHLAS ◽  
THEODORE P. GOLDSTEIN ◽  
DAVID H. ROSENBLATT ◽  
MARVIN KIRSCH ◽  
ARNOLD M. SELIGMAN
Keyword(s):  
Aromatic Amines ◽  
Diazonium Salt ◽  
Tissue Sections ◽  
Coupling Techniques ◽  
Diazonium Ions ◽  
Coupling Rate ◽  
Diazonium Ion ◽  
Hydroxy Compounds ◽  
Positive Groups ◽  
Electro Negativity

Reliability of enzymatic localization in tissue sections by the simultaneous coupling techniques is dependent to a great extent upon the speed of coupling. Therefore, the influence on coupling rate of the structure of the diazonium ion and of the coupling component was studied. Electro-negative groups in the diazonium ion increase the rate of coupling, while the same groups in the coupling component decrease the rate. Electro-positive groups in the coupling component accelerate coupling, but slow it when present in the diazonium ion. The relation of coupling rate and electro-negativity of the substituents in the diazonium ion follows Hammett's equation (8). Although the relations is linear on coupling with aromatic hydroxy compounds, it is not so with aromatic amines. The most active diazonium ions showed no increase in coupling rate with aromatic amines. This suggests that for those enzymes hydrolyzing an ester link, increase of coupling rate might be accomplished by modifying the structure of either the coupling component used in the substrate or the diazonium salt. However, for enzymes splitting amide linkages, the only possibility of improving the localization is by modifying the structure of the coupling component.

Photolysis of Di-t-butylnitroxide

1982 ◽  
Vol 35 (3) ◽  
pp. 509 ◽  
Author(s):  
JM Coxon ◽  
E Patsalides
Keyword(s):  
Excited State ◽  
Light Intensity ◽  
Crystalline Solid ◽  
First Order ◽  
Deaerated Solution

Di-t-butylnitroxide (1) on photolysis in methylcyclohexane gives in addition to t-butoxy(di-t-buty1)-amine (7) and photolabile 2-methyl-2-nitrosopropane (2) a low yield of a white crystalline solid identified as a mixture of di-t-butylhydroxylammonium nitrate (13) and nitrite (14). Photolysis proceeds from the excited state produced by a π-π* transition, and in aerated solution is first order both with respect to nitroxide and light intensity. More complex kinetics are observed in deaerated solution.

THE IDENTIFICATION OF AZOXY COMPOUNDS

1949 ◽  
Vol 27b (12) ◽  
pp. 897-901 ◽  
Author(s):  
Roger Gaudry ◽  
Karl F. Keirstead
Keyword(s):  
Sulphuric Acid ◽  
Zinc Dust ◽  
Para Isomer ◽  
Azo Compound ◽  
Azoxy Compounds ◽  
Azoxy Compound ◽  
First Time

An azoxy compound can be treated with concentrated sulphuric acid to produce a nydroxyazo product consisting chiefly of the para isomer. This reaction, the Wallach rearrangement, is the basis for a suggested generic test for an azoxy compound. For the identification of a given azoxy compound, two derivatives are suggested: the hydrazo compound produced by the reduction of the azoxy compound by zinc dust, and the azo compound produced by the oxidation of the hydrazo compound. These compounds are described for the first time: 2,2′-dichloro-4-hydroxyazobenzene, 2,5′,2,5′-tetrachloro-4-hydroxyazobenzene, 2,2′-dimethoxy-5,5′-dichloroazobenzene, 3,3′,4,4′-tetrachlorohydrazobenzene, 2,2′-dimethyl-3,3′-dichlorohydrazobenzene, and 2,2′-dimethoxy-5,5′-dichlorohydrazo-benzene.

The Characteristics of All-Optical Switching and Modulation in Phenoxy-Phthalocyanines Liquid

2013 ◽  
Vol 284-287 ◽  
pp. 2830-2834
Author(s):  
Yun Dong Zhang ◽  
Cheng Bao Yao ◽  
Hai Tao Yin ◽  
Chang Qiu Yu ◽  
Jin Li ◽  
...  
Keyword(s):  
Excited State ◽  
Light Intensity ◽  
Response Time ◽  
Optical Switching ◽  
Pump Light ◽  
Pump Probe ◽  
All Optical ◽  
Probe Experiment ◽  
Pump Probe Experiment ◽  
All Optical Switching

We present our experimental results on the measurements of excited state dynamics in 2, 9, 16, 23-phenoxy-phthalocyanine (Pc1) and 2, 9, 16, 23-phenoxy-phthalocyanine-zinc (Pc2) using the pump-probe experiment. The results show that the All-Optical Switching (A-OS) response time of Pc2 longer than that of Pc1, and switch-off and -on times of A-OS for Pc2 are 1.2 and 11.6 μs and for Pc1 are 2.3 and 7.8 μs at the same intensity. Moreover, analysis of modulation characteristics of A-OS shows that the stronger the light intensity of the pump light is, the smaller the normalized transmittance is and the shorter the response time of A-OS is. The consequences of such short lifetimes are also discussed in view of the strong A-OS properties of these molecules.

scholarly journals Coherent Population Trapping Resonances in Cs Atomic Vapor Layers of Micrometric Thickness

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
A. Krasteva ◽  
D. Slavov ◽  
S. Cartaleva
Keyword(s):  
Excited State ◽  
Light Intensity ◽  
Electromagnetically Induced Transparency ◽  
Elastic Interaction ◽  
Coherent Population Trapping ◽  
Sign Reversal ◽  
Resonance Amplitude ◽  
Electromagnetically Induced Absorption ◽  
Induced Transparency ◽  
Population Trapping

We report on a novel behavior of the electromagnetically induced absorption (EIA) resonance observed on theD2line of Cs for atoms confined in cells with micrometric thickness. With the enhancement of light intensity, the EIA resonance amplitude suffers from fast reduction, and even at very low intensity (W < 1 mW/cm2), resonance sign reversal takes place and electromagnetically induced transparency (EIT) resonance is observed. Similar EIA resonance transformation to EIT one is not observed in conventional cm-size cells. A theoretical model is proposed to analyze the physical processes behind the EIA resonance sign reversal with light intensity. The model involves elastic interactions between Cs atoms as well as elastic interaction of atom micrometric-cell windows, both resulting in depolarization of excited state which can lead to the new observations. The effect of excited state depolarization is confirmed also by the fluorescence (absorption) spectra measurement in micrometric cells with different thicknesses.

Exergy Analysis as a Tool for Decision Making on Substrate Concentration and Light Intensity in Photobiological Hydrogen Production

2015 ◽  
Vol 4 (3) ◽  
pp. 429-440 ◽  
Author(s):  
Ali Dadak ◽  
Mortaza Aghbashlo ◽  
Meisam Tabatabaei ◽  
Ghasem Najafpour ◽  
Habibollah Younesi
Keyword(s):  
Decision Making ◽  
Hydrogen Production ◽  
Light Intensity ◽  
Substrate Concentration ◽  
Exergy Analysis

Kinetics of reactions of 1,2,4-triazole-3-diazonium ions with phenol and with hydroxyl ion

1985 ◽  
Vol 50 (3) ◽  
pp. 658-674
Author(s):  
Vladimír Macháček ◽  
Josef Kořínek ◽  
Daniela Kreuzigová ◽  
Vojeslav Štěrba
Keyword(s):  
Main Reaction ◽  
Basic Medium ◽  
Phenyl Derivative ◽  
Rate Limiting Step ◽  
Diffusion Controlled ◽  
Hydroxyl Ion ◽  
Diazonium Ions ◽  
Diazonium Ion ◽  
Hydroxy Compounds ◽  
Intramolecular Hydrogen

5-Methyl- and 5-phenyl-l,2,4-triazole-3-diazonium ions (IIIa, IIIb) react with undissociated phenol in diluted hydrochloric acid. At pH > 1 the reactions with phenolate ions become kinetically significant, their bimolecular rate constants approaching those of the diffusion-controlled reactions. At the same time, the diazonium ions are dissociated into the dipolar ions IIIb and IVb. At pH > 4 (for the phenyl derivative) and pH > 5 (for the methyl derivative), the reaction of the dipolar ions with phenolate ion becomes the main reaction path. The rate constant of the reaction of the dipolar ion IIIb with hydroxyl ion (3 . 103 l mol-1 s-1) is comparable with that of the analogous reaction of benzenediazonium ion, but the reverse reaction of the dipolar ion IIIb is slower by about 5 orders of magnitude, and the pKA value of the diazo hydroxide formed is higher by about 4 units than that of benzenediazo hydroxide. The high stability of the heterocyclic diazo hydroxide and its low acidity are explained by formation of a strong intramolecular hydrogen bond. In sodium hydroxide solutions, the (Z)-diazotate IIId initially formed is transformed into the (E)-isomer (the corresponding half-life being about 10 h) which, in contrast to the (Z)-isorner, does not practically react with aromatic hydroxy compounds in basic medium. The transformation of the (E)-isomer to the diazonium ion is general acid-catalyzed reaction. Transformation of nitrosamine into diazo hydroxide is suggested to be the rate-limiting step of this reaction in solutions of pH < 5.

scholarly journals Vital role of entropy in photochirogenesis

2001 ◽  
Vol 73 (3) ◽  
pp. 475-480 ◽  
Author(s):  
Yoshihisa Inoue ◽  
Norimitsu Sugahara ◽  
Takehiko Wada
Keyword(s):  
Excited State ◽  
Substrate Concentration ◽  
Vital Role ◽  
Photochemical Reactions ◽  
External Factors ◽  
Steric Interactions ◽  
Global View ◽  
Potential Applications ◽  
Effects Of Temperature

The effects of temperature, pressure, solvent, and substrate concentration upon several enantio- and diastereodifferentiating photochemical reactions have been investigated and discussed in detail. These entropy-related external factors, which manipulate the weak electronic and steric interactions in the excited state, dynamically control the stereochemical outcome of asymmetric photochemical reactions, and even switch the product chirality. A global view on the "entropy chemistry" and its potential applications are also discussed.

Open-chain nitrogen compounds. Part VI. The formation of bis(1-aryl-3- methyltriazen-3-ylmethyl) methylamines in the reaction of diazonium ions with mixtures of formaldehyde and methylamine

1984 ◽  
Vol 62 (4) ◽  
pp. 749-754 ◽  
Author(s):  
Hartford W. Manning ◽  
Chantal M. Hemens ◽  
Ronald J. LaFrance ◽  
York Tang ◽  
Keith Vaughan
Keyword(s):  
Diazonium Salts ◽  
Mechanism Of Formation ◽  
Open Chain ◽  
Cyclic Trimer ◽  
Anti Tumour Activity ◽  
Diazonium Ions ◽  
Diazonium Ion ◽  
A Minor ◽  
Identical Product ◽  
Tumour Activity

The synthesis of a series of N,N-bis(1-aryl-3-methyltriazen-3-ylmethyl) methylamines from coupling diazonium salts with mixtures of methylamine and formaldehyde is described. These novel bis-triazenes, or heptazanonadienes, have significant anti-tumour activity against the TLX5 lymphoma in mouse. The mechanism of formation of these triazenes is discussed with reference to the implication to the presumed equilibria taking place in the methylamine/formaldehyde solution. The formation of the bis-triazene is usually accompanied by the formation of a 3-hydroxymethyitriazene, and it has been shown that the hydroxymethyltriazene can be transformed into the bis-triazene. The proportions of the two products are strongly influenced by the relative amounts of methylamine and formaldehyde. Coupling the p-bromobenzenediazonium salt to a 1:1 methylamine/formaldehyde mixture affords mainly the bis-triazene, whereas a 1:50 mixture gives almost totally the hydroxymethyl triazene. These results suggest that the two triazenes arise from diazonium coupling to different species in the amine/formaldehyde mixture; this hypothesis is supported by the formation of identical product mixtures from coupling the diazonium ion with (a) a 1:1 MeNH2/CH2O mixture, and (b) the cyclic trimer of the carbinolamine MeNHCH2OH, and by the identification of a minor product from the reaction of p-chlorobenzenediazonium fluoroborate with MeNH2/CH2O as bis(1-p-chlorophenyl-3-methyltriazen-3-yl) methane.

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