Search results for "Halogen"
showing 10 items of 434 documents
4-Alkenyl-1,2,3-thiadiazole
1986
Die Titelverbindungen 5 werden aus entsprechenden Alkylderivaten durch Bromierung/Dehydrobromierung (Weg A) oder durch Wittig-Reaktion (Weg B) dargestellt. Mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion entstehen unter Erhaltung des Thiadiazolrings die Monoaddukte 12. 4-Alkenyl-1,2,3-thiadiazoles The title compounds 5 are prepared from the corresponding alkyl derivatives by bromination/dehydrobromination (route A) or by Wittig reaction (route B). 4-Phenyl-4H-1,2,4-triazole-3,5-dione yields the monoadducts 12 by maintenance of the thiadiazole ring.
Attractive halogen···halogen interactions in crystal structure of trans-dibromogold(III) complex
2020
Abstract A synthesis of the trans-dibromogold(III) t-Bu-Xantphos complex and its self-assembly into infinite 1-dimensional chain in the solid state is reported. The new complex characterized using elemental analyses (C, H, N), ESI-MS, 1H and 13C NMR techniques and X-ray diffraction analysis. Results of DFT calculations followed by the topological analysis of the electron density distribution within the framework of QTAIM method at the ωB97XD/DZP-DKH level of theory reveal that strength of attractive intermolecular non-covalent interactions Br···Br in the crystal is 1.2–1.6 kcal/mol.
Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation
2017
Transition-metal oxide nanoparticles and molecular coordination compounds are highlighted as functional mimics of halogenating enzymes. These enzymes are involved in halometabolite biosynthesis. Their activity is based upon the formation of hypohalous acids from halides and hydrogen peroxide or oxygen, which form bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities in follow-up reactions. Therefore, enzyme mimics and halogenating enzymes may be valuable tools to combat biofilm formation. Here, halogenating enzyme models are briefly described, enzyme mimics are classified according to their catalytic functions, and current knowledge about th…
Mass spectra of halogenated esters 6—Methyl esters of some trihalogenated propanoic and butanoic acids
1984
The mass spectral fragmentation of trihalogenated methyl esters, formed in the reactions of monochlorinated methyl propenoates and 2-butenoates with Cl2, BrCl and Br2, have been investigated. In most cases α-cleavage gives the base peak, [COOCH3]+, the peaks originating from the subsequent losses of one or two halogen atoms also being abundant. The primary loss of a halogen atom is more prominent in the C4 derivatives, Br˙ and Cl˙ being preferentially lost from the 2- and 3-positions, respectively. The McLafferty rearrangement yields in one case the base peak; the 2-halo compounds could in general be distinguished by that fragmentation. Typical for all 2-bromo-substituted methyl butanoates …
On the aromaticity of uracil and its 5-halogeno derivatives as revealed by theoretically derived geometric and magnetic indexes
2020
AbstractThe problem of aromaticity in heterocyclic rings of uracil and its 5-halogenoderivatives (5XU) was analyzed theoretically by calculating modified harmonic oscillator model of aromaticity (HOMA) for Heterocycle Electron Delocalization (HOMHED), nucleus-independent chemical shift parameters (NICS) and the so-called scan experiments, using helium-3 atom as a magnetic probe. The impact of halogen electronegativity on C5 atom’s NBO charges was also investigated. Water, as a polar environment, has a negligible impact on 5XU aromaticity. The most stable diketo tautomer shows a very low aromaticity while the “rare” dihydroxy form (tautomer No 6) is aromatic and resembles benzene. This is in…
Halogen bonding enhances nonlinear optical response in poled supramolecular polymers
2015
We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems. acceptedVersion Peer reviewed
4-Vinylphthalic anhydride
1994
4-Vinylphthalic anhydride can be prepared from phthalic acid via bromination and subsequent olefination (Heck-reaction). Homo- and copolymerization with styrene was accomplished using AIBN as initiator. The copolymer compositions were determined by infrared-spectroscopy. The copolymerization parameters are rs=0,15 and rVPA=3,09, the corresponding Q, e values of 4-vinylphthalic anhydride are estimated as Q=3,34 and e=0.09.
Internal rotation of 1,2-dichloroethane in haloalkane dehalogenase. A test case for analyzing electrostatic effects in enzymes
2003
1,2-Dichoroethane (DCE) is a prototypical molecule for studying electrostatic solvent effects on molecular conformation as far as rotation around the carbon−carbon bond notably changes the electric...
Highly Luminescent Half-Lantern Cyclometalated Platinum(II) Complex: Synthesis, Structure, Luminescence Studies, and Reactivity.
2012
The half-lantern compound [{Pt(bzq)(μ-C 7H 4NS 2-κN,S)} 2]•Me 2CO (1) was obtained by reaction of equimolar amounts of potassium 2-mercaptobenzothiazolate (KC 7H 4NS 2) and [Pt(bzq)(NCMe) 2]ClO 4. The Pt(II)•••Pt(II) separation in the neutral complex [{Pt(bzq)(μ-C 7H 4NS 2-κN,S)} 2] is 2.910 (2) Å, this being among the shortest observed in half-lantern divalent platinum complexes. Within the complex, the benzo[h]quinoline (bzq) groups lie in close proximity with most C•••C distances being between 3.3 and 3.7 Å, which is indicative of significant π-π interactions. The reaction of 1 with halogens X 2 (X 2 = Cl 2, Br 2, or I 2) proceeds with a two-electron oxidation to give the corresponding d…
Oxidative halogenation of substituted pyrroles with Cu(II). PartIV.Bromination of 2-(2′-hydroxybenzoyl)pyrrole. A new synthesis of bioactive analogs …
1994
The selective bromination with copper(II) bromide of the pyrrole ring in 2-(2'-hydroxybenzoyl)pyrrole (II) in the heterogeneous phase is des- cribed giving in almost quantitative yield the 4,5-dibromo derivative (VI). The subsequent introduction of halogen into the phenol moiety was observed when the reaction was perfomed in the homogeneous phase with an excess of halogenating agent. The pentabromo derivative (IX), a com- pound very active against Staphylococcus aureus (mic=17 nmoles per dm -3 ), was obtained by exhaustive bromination of the title compound. Poor yields of chloro derivatives of (II) were obtained by reaction of the parent compound with copper(II) chloride