Positive and negative ion mass spectra of oxygen,sulphur and selenium 2,1,3-benzodiazoles

The 70 eV positive and negative ion mass spectra of the oxygen, sulphur and selenium 2,1,3-benzodiazoles have been studied. The influence of hetero atom on the fragmentation modes of the benzodiazole molecular ions has been discussed.     

Studies in the field of 2,1,3-thia- and -selenadiazoles

The results of studies on 2,1,3-thiadiazole, benzo-2,1,3-thiadiazole, benzo-2,1,3-selenadiazole, and their derivatives by chemical, physicochemical, and physical methods give no grounds for assuming that they have a quinoid structure. These results permit the statement that these heterocycles containing quatervalent sulfur or selenium are typical heteroaromatic systems satisfying Hückel's (4n+2) rule.For part LV, see [1].     

Dipole moments of hydroxy- and methoxy-azobenzene derivatives

The dipole moments of some 4-hydroxy and 4-methoxyazobenzene derivatives were measured in benzene solutions. Results show that (a) there are no appreciable mesomeric interactions between the polar groups in the molecule; (b) evidence is obtained for the hindered rotation of the OH and OCH₃, groups; and (c) the difference between the dipole moments of the title compounds and those of the corresponding benzene derivatives can be referred both to the extension of the conjugated system and to the value of the interaction moment. Experimental results are discussed with the aid of CNDO/2 calculations.     

Reactions of benzo-1,2,3-dithiazolium salts and their selenium analogs with amines

The corresponding 6-arylamino derivatives were obtained by reaction of 6-chloro, 6-bromo, and 6-methoxy derivatives of benzo-1,2,3-dithiazolium and their selenium analogs — benzo-1,2,3-thiaselenazolium, benzo-2,1,3-thiaselenazolium, and benzo-1,2,3-diselenazolium salts — with aromatic amines. The 6-methoxy derivatives also react with acetates of secondary aliphatic amines, whereas in the case of the chloro derivatives attack is directed to the heteroring. 6-Aryl(dialkyl)amino derivatives of dithiazolium and 1,2,3-thiaselenazolium salts are protonated in concentrated sulfuric acid at the exocyclic nitrogen atom. The analogous derivatives of 2,1,3-thiaselenazolium and diselenazolium salts under the same conditions form a tautomeric mixture of dications, the position of the equilibrium between which depends on the substituent. The electronic and PMR spectra of the amination products are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1499–1502, November, 1977.     

A dipole moment study of organo-chalcogen compoun

Analysis of the dipole moments of chalcogenoanisoles, the directions of which are given by those of their p-bromo derivatives, shows that the mesomeric moment decreases on passing from anisole to thioanisole, selenoanisole and telluroanisole (m = 1.1, 0.5, 0.25 and 0.18 D, respectively). In p-nitrochalcogenoanisoles and 1-chalcogenochroman-4-ones the interaction moment follows the reverse order, which is ascribed to the increasing sensitivity of the chalcogen mesomeric moment to the chalcogen atomic number and polarizability. The less-hindered (Te, O)-cis conformation is preferred for 2-acyl-3-methyltellurothiophenes and 3-acyl-2-methyltellurothiophenes (acyl: formyl or acetyl), and 3-formyl-4-methyltellurothiophene. Rotational isomerism in bis(2-furyl), bis(2-thienyl), bis(3-thienyl) and bis(2-selenienyl) ditelluride is also examined, and the dipole moments of 1-chalcogenochroman-4-ones, 2-chalcogenochroman-1-ones and 2-chalco-genochrom-1-ones analyzed.     

Structures and reactivities of benzo-1,2,3-dithiazolium salts and their selenium analogs

A number of benzo-1,2,3-dithiazolium chlorides (I) and their selenium analogs — benzo-1,2,3-thiaselenazolium, benzo-2,1,3-thiaselenazolium, and benzo-1,2,3-diselenazolium salts — were synthesized. The electronic structures and reactivities of the I cation and salts I–IV are discussed on the basis of a quantum-chemical calculation of cation I and the PMR spectra of salts I–IV. Successive substitution of the sulfur atoms in the I cation by selenium atoms, particularly in the 2 position, substantially increases the degree of transfer of positive charge to the condensed benzene ring. The trend of the nucleophilic reactivities of 6-methoxy derivatives of salts I–IV in the reaction with aromatic amines is the same as the trend of the degree of localization of the positive charge in the 6 position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 912–916, July, 1978.     

Ab initio density-functional study of the bridging addition of acrylonitrile on the Si(100) surface

Acrylonitrile may react with the Si(100) surface in a number of ways. Fifteen different configurations have been identified. This study which complements an earlier study devoted to cycloadditions and bonds involving a single atom deals essentially with configurations involving cumulative double bonds. Factors affecting the relative stability of various mesomeric forms are shown to be the proximity to tetrahedral geometry and the compatibility of the dipole form with buckled structures. Tripods are shown to be a way to accommodate a priori unfavorable structures.     

Oxidationsreaktionen methyl-substituierter 2,1,3-Benzothiadiazole und 2,1,3-Benzoselenadiazole mit Selen-dioxid

Oxidation Reactions of Methyl Substituted 2,1,3-Benzothiadiazoles and 2,1,3-Benzoselenadiazoles with Selenium Dioxide The synthesis 5–8 by oxidation of 4-methyl-( 1 ),5-methyl( 2 ), 5,6-dimethyl-2,1,3-benzoselenadiazole ( 3 ), and 5,6-dimethyl-2,1,3-benzothiadiazole ( 4 ), respectively, with selenium dioxide as well as their spectroscopic properties are described.     

硒芳香杂环化合物的微波固相合成

许多含硒杂环化合物具有抗肿瘤、抗病毒等生物活性及超导性。微波技术由于能量利用率高,操作简便,无污染等优点,已在有机合成中得到了广泛的应用。本文采用微波辐射固相合成法合成了如下目标化合物：     

Approaches to charge calculations in molecular mechanics. 2 Resonance effects in conjugated systems

A previously published scheme of estimating atomic charges in haloalkanes is extended to include olefines, alcohols amines, acids, ethers, and amides. In the conjugated systems the effects of mesomeric transfer of charge are explicitly included. Generally good agreement with the observed dipole moments of these compounds and their substituted derivatives is found. The atomic charges so obtained are compared with those of other semiempirical and quantum-mechanical calculations for the amide group. The charges so obtained fall within the range of values obtained by these other schemes, supporting the general validity of this approach.     

Electric dipole moments and molecular structure of aliphatic nitro compounds and oximes

Using the treatment of Smith et al. charge distributions in and consequently the dipole moments of some aliphatic nitro compounds and oximes have been evaluated. The mesomeric moment derived as a difference between the calculated and the observed values gives a clear picture as to how the positive (+M) and the negative (−M) mesomeric effects operate in such systems.     

Electronegativity and inductive and mesomeric parameters of atomic groups: A semiempirical quantum chemical estimation

The electronegativity, the inductive parameter, and the mesomeric dipole moments of substituents depend on the electronic structure characteristics of organic molecules calculated by the CNDO/2, INDO, MINDO, MINDO/3, MNDO, and AMI methods. It is shown that the electronegativity as well as the inductive and mesomeric characteristics of atomic groups may be estimated by semiempirical quantum chemical methods.     

Conformations of highly hindered aryl ethers: XV. Mesomeric moments in m-dinitrobenzenes

The dipole moments of fourteen m-dinitrobenzenes with different substituents (OMe, CN, CH₃, CHO, Cl, CF₃, COOMe, F, Br, NH₂) in various positions were measured in order to study mesomeric interactions. Inclusion of conformational considerations permitted estimates to be made for the mesomeric moments of these groups at given positions. The values obtained could be applied with consistent results to a total of forty m-dinitrobenzenes, including others previously reported. The mesomeric moment increments deduced, compared with substituted benzenes possessing no nitro groups, were found to be only slightly larger than in non-nitro substituted benzenes (compared with substituted alkanes), which would indicate a reluctance of the extended π system of m-dinitrobenzene to interact with other substituents present, in any way other than by direct extension of the π network.One apparent case of intermolecular electron donor-acceptor complex formation was detected. The measured dipole moment of o-iodoanisole indicates a planar anti conformation for the methoxyl group.     

Chalcogen Bonding “2S–2N Squares” versus Competing Interactions: Exploring the Recognition Properties of Sulfur

Chalcogen bonding (CB) is the focus of increased attention for its applications in medicinal chemistry, materials science, and crystal engineering. However, the origin of sulfur's recognition properties remains controversial, and experimental evidence for supporting theories is still emerging. Here, a comprehensive evaluation of sulfur CB interactions is presented by investigating 2,1,3-benzothiadiazole X-ray crystallographic structures gathered from the Cambridge Structure Database (CSD), Protein Data Bank (PDB), and own laboratory findings. Through the systematic analysis of substituent effects on a subset library of over thirty benzothiadiazole derivatives, the competing interactions have been categorized into four main classes, namely 2S–2N CB square, halogen bonding (XB), S ⋅⋅⋅ S, and hydrogen-bonding (HB). A geometric model is employed to characterize the 2S–2N CB square motifs and discuss the role of electrostatic, dipole, and orbital contributions toward the interaction.     

Investigation of 2, 1, 3-thia- and 2, 1, 3 selenadiazoles

The nitration of naphtho[1,2-d][2,1,3]thiadiazole under the conditions that are normally used for aromatic compounds gives a mixture of 6- and 9-nitronaphthothiadiazoles, which can be reduced to 6- and 9-amino derivatives, respectively. 6-Hydroxynaphthothiadiazole is obtained from 6-aminonaphthothiadiazole by the Sandmeyer reaction, while 8-hydroxynaphthothiadiazole is converted to the 8-amino derivative under the conditions of the Bucherer reaction. 4-Carboxy-5-(o-carboxyphenyl)-2,1,3-thiadiazole was obtained by the oxidation of naphtho[1,2-d][2,1,3]-thiadiazole with a potassium dichromate-dilute sulfuric acid mixture.See [1] for communication LXVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1972.     

Core ionization energies and multi-peak structure of esca bands in some pentatomic heterocyclic compounds

The core ionization energy and the multi-peak structures of ESCA bands in furan, pyrrole, thiophen and their saturated homologues were obtained. Significant change of ESCA data is observed on going from the saturated to the aromatic compounds. The variations in the core ionization energies seem connected to the mesomeric drift of charge from the heteroatom to the carbon atoms in the aromatic derivatives. Shake-up processes involving charge-transfer transitions are considered to be the major responsible of the observed multi-peak structure in the aromatic compounds.     

Nitro derivatives of 2,1,3-benzothiadiazole 1-oxides: synthesis,structural study,and NO release

A convenient one-pot synthesis of nitro derivatives of 2,1,3-benzothiadiazole 1-oxides by the reaction of o-nitroanilines with sulfur monochloride was developed. The structural features of 4-nitrobenzothiadiazole and its N-oxide were considered. High in vitro release of nitric oxide (69%) was found for a 6-nitro-2,1,3-benzothiadiazole sample by the Griess assay, which indicated good prospects for this class of compounds.     

Dependence of molar heat of solution of certain polar aromatic compounds on composition and structure of sorbate molecules,as determined by gas-liquid chromatography

Gas-liquid chromatography has been used in determining the relative molar heat of dissolution of 32 aromatic hydrocarbons and their polar derivatives in the polydimethylsiloxane stationary phase OV-101. A previously developed semiempirical method for the calculation of molar heats of dissolution on the basis of microparameters of the sorbate molecules is applicable to the system studied in the present work. Interaction of -electrons of the benzene ring with the stationary phase is one of the main factors determining the molar heat of dissolution of aromatic hydrocarbons and their polar derivatives in the polymethylsiloxane stationary phase, as a consequence, the magnitude and direction of the mesomeric effect of the substituent play an important role. The dipole moment of the sorbate has a significant influence on the manifestation of orientational interaction only for localized microdipoles with high polarity.Translated from Teoreticheskava i Ékperimental'naya Khimiya, Vol. 25, No. 1, pp. 61–70, January–February, 1989.     

Synthesis and intramolecular cyclization of bisthiadiazinylmethane derivatives

Bisthiadiazinylmethane derivatives obtained from 1,2,6-thiadiazine 1,1-dioxides and formaldehyde, undergo unusual intramolecular cyclizations to thiadiazino [4,3-g] [2,1,3] benzothiadiazine tetraoxides. The structures of the newly synthesized compounds are discussed on the basis of ¹H and ¹³C-NMR data and X-ray analysis.