Showing papers on "Halogen published in 1988"

Sodium perfluoroalkane carboxylates as sources of perfluoroalkyl groups

Abstract: Sodium trifluoroacetate, in the presence of copper(I) iodide, is used as a source of trifluoromethyl to replace halogen by trifluoromethyl in benzenoid and heterocyclic aromatic systems, as well as in alkenyl and alkyl halogen compounds. The mechanism of this interesting copper-assisted process has been explored and an intermediate of the form [CF3Cul]– is proposed. Introduction of higher perfluoroalkyl groups from their respective sodium perfluoroalkane carboxylates has been demonstrated and the mechanistic features are compared with those of the trifluoromethylation process.

Sources of halogens in the environment, influences on human and animal health.

Abstract: Of the halogens, fluorine has the highest crustal abundance (544 mg/kg) while iodine has the lowest (0.25 mg/kg), however, chlorine is by far the most abundant halogen in the cosmos. The geochemistries of the four naturally occurring halogens have some similarities with fluorine, chlorine and bromine being classified as lithophile elements while iodine is more chalcophile in nature. Bromine and iodine behave in a similar fashion in the secondary environment and could be classified as biophile elements being concentrated in organic matter. Chlorine, bromine and iodine are strongly enriched in the sea while iodine and to a lesser extent bromine are further concentrated in the marine algae.Apart from the occurrence of fluorine in fluorite (CaF2) there are few commonly occurring minerals which contain the halogens as essential constituents. In the igneous environment fluorine and chlorine tend to occupy hydroxyl lattice sites in micas, amphiboles, apatites etc., while in sediments clays can contain appreciable quantities of these elements. Bromine and iodine, however, would be unlikely to fit into the lattice sites of common rock-forming minerals.Bromine, like iodine, is probably volatilised from the marine environment and is carried on to land surfaces. This behaviour of iodine and bromine is reflected in the increased I/CI and Br/CI ratios of surface run-off in continental compared with near coastal environments.Limited information on the soil geochemistry of the halogens suggests that the soil contents of chlorine, bromine and iodine are influenced by proximity to the sea. Soil fluorine, however, is generally dependent on its content in the parent material. In some areas pollutant sources of the halogens contribute appreciably to their concentration in the environment.Iodine and chlorine are essential elements for mammals and fluorine has been shown to have beneficial effects on bone and tooth formation. However, excess quantities of dietary fluorine can be harmful. It is possible, in view of its ubiquitous occurrence in the biosphere, that bromine has a hitherto unknown function in human and animal health.

Bond Ionicity in Halogen Silver Interaction

Abstract: : The nature of the bonding between halogen atoms (F, CI and Br) and the Ag (111) surface has been investigated by analyzing ab initio Hartree- Fock wave functions for cluster models of the Ag surface and a halogen atom. Using a variety of criteria, we conclude that the bonding is ionic and that the halogen ionicity is essentially -1. The measures of ionicity reported are a) the expectation value of a projection operator which provides an indication of the total charge associated with the halogen atom, b) the analysis of the dipole moment curve as function of distance, c) the effect on the equilibrium bond distances of an uniform external electric field, and d) the decomposition of the interaction energy into the sum of different contributions. This latter analysis shows that the bonding arises, almost entirely, from the Coulomb attraction between the charged halogen and the metal and from polarization fo the two sub- units. Fluorine, Chlorine, Bromine, Silver.

Process and a composition for immunizing plants against diseases

Abstract: A method and composition for the immunization of healthy useful plants against plant diseases containing as active ingredients compounds of formula ##STR1## in which: X is hydrogen, halogen, hydroxy, methyl, methoxy, HOOC or MOOC; Y is hydrogen, halogen, SO3 H, SO3 M, nitro, hydroxy or amino, M being the molar equivalent of an alkali metal or alkaline earth metal ion that is formed from a corresponding base or basic compound; and Z is cyano or --CO--A; A represents either --OH or --SH, the hydrogen atom of which may also be replaced by the molar equivalent of an inorganic or organic cationic residue, or wherein A represents any other organic residue which has a molecular weight of less than 900 and which may also contain one, or more than one, hetero atom, including the salts of the phytophysiologically tolerable 7-carboxylic acid or 7-thiocarboxylic acid with primary, secondary or tertiary amines or with inorganic bases.

Photochemistry of α-chloro- and α-bromoacetophenone. Determination of extinction coefficients for halogen–benzene complexes

Abstract: The photochemical dehalogenation of α-haloacetophenones (Cl, Br) in benzene solution has been examined under conditions of continuous and pulsed laser irradiation. Product and quantum yield studies indicate that carbon-halogen bond cleavage occurs with quantum yields of 0.88 and 0.41 for α-chloro- and α-bromoacetophenone, respectively. These values are based on trapping studies in which the PhC(O)ĊH2 radicals produced photochemically are scavenged by hydrogen donors such as benzenethiol. Laser flash photolysis studies lead to intense transient signals due to benzene–halogen complexes. Combination of transient data and quantum yields lead to extinction coefficients of 1 800 and 23 700 M−1 cm−1 for the chlorine (490 nm) and bromine (550 nm) complexes, respectively.

Fluorine and chlorine apicophilicities in five-coordinated phosphorus and silicon compounds via molecular orbital calculations. A model for nucleophilic substitution

Abstract: Comparative ab initio molecular orbital calculations on pentacoordinated phosphorus and silicon model states are used to establish apicophilicities in a series of trigonal-bipyramidal molecules composed of all combinations of the ligand atoms, hydrogen, chlorine, and fluorine. In agreement with experimental observations, it is shown that chlorine is in general more apicophilic than fluorine except when the collective electronegativity of equatorial atoms is increased sufficiently, e.g., as in the PCl n Fs-n series. The crossover in halogen apicophilicity for silicon has an even greater electronegativity requirement in equatorial sites than that for phosphorus. Further, as applied in nucleophilic substitution reactions, the apicophilicity of the leaving group is diminished by the composition of equatorial ligands in the order Cl > F > H. In contrast, the apicophilicity of the leaving group is enhanced by the opposite apical atom in this same order, Cl > F > H, in all cases except that in which the...

Process and composition for drying of gaseous hydrogen halides

Abstract: A process for drying a gaseous hydrogen halide of the formula HX, wherein X is bromine, Chlorine, FLuorine, or iodine, to remove water impurity therefrom, in which a scavenger precursor composition is provided, including a support having associated therewith partially or fully alkylated metal alkyl compounds or pendant groups. The precursor composition is reacted with gaseous hydrogen halide to convert the metal alkyl compounds and/or pendant functional groups to the corresponding metal halide compounds and/or pendant functional groups, which in turn react with the water impurity to produce an essentially completely water-free (below 0.1 ppm) gaseous hydrogen halide effluent. The process of the invention has utility for producing high purity, anhydrous gaseous hydrogen halides for semiconductor manufacturing operations.

Vanadium tetrachloride stabilization

Abstract: Solutions of VCl₄ in inert organic solvent are stabilized by incorporation of decomposition retardants being halogenated organic compounds having at least two halogen atoms attached to the same carbon atom and activated by adjacent electron donor groups or carbon-carbon double bonds. One of the especially preferred stabilizers is butyl perchlorocrotonate. The solutions are useful in polymerization processes.

Synthesis and properties of polyamides derived from systematically halogenated terephthalic acids with fluorine, chlorine, or bromine atoms

Abstract: Aromatic polyamides were prepared from systematically halogenated terephthalic acids with hexamethylene diamine, piperazine, 4,4′-diaminodiphenylether and p-phenylene diamine by interfacial or low temperature solution polycondensation. The halogenated terephthalic acids used have mono-, di-, or tetra-substituted fluorine, chlorine, or bromine atoms on the benzene ring. The nonhalogenated terephthalic acid was also used for the comparison. The effects of halogen substitution on the benzene ring on the synthesis and some properties of polymers were examined. Reduced specific viscosity decreased in the order F > Cl > Br by halogen substitution. The incorporation of halogen substituents on the ring led to a decrease of crystallinity and fluoro-substituents hindered the crystallization more strongly. The melting point (Tm) decreased in the order F > Cl > Br by mono-substitution, and Br > Cl > F by di-and tetra-substitution. The change of Tm caused by the difference of the number of halogen substituents differed depending on the rigidity of polymer chains. The flame-retardancy estimated by thermogravimetry, self-ignition, and flash-ignition test increased with increasing halogen content of the polymers. Solubility increased remarkably by halogen substitution. The peak temperature of tan δ decreased by halogen substitution. Some discussion was made on these effects of halogen substitution.

Compounds used as intermediates in the preparations of non-radioactive biological probes

Abstract: ##STR1## wherein R 1 to R 4 , which may be the same or different, are selected from the group consisting of H, alkyl of 1 to 5 carbon atoms, NO 2 , halogen, --COOH, or --NH 2 ; wherein R 5 , R 6 , R 7 , R 8 which may be the same or different are selected from the group consisting of H, alkyl of 1 to 5 carbon atoms and halogen; wherein n is an integer of 0 to 5 m is an integer of 1 to 10 p is an integer of 0 to 1 a is an integer of 0 to 1 b is an integer of 1 to 10, wherein if a is 1 then b is 1, and wherein the moiety ##STR2## includes at least 5 carbon atoms and wherein D is selected from the group consisting of ##STR3## The compounds may be used as intermediates in the preparation of non-radioactive biological probes.

Acid stable dideoxynucleosides active against the cytopathic effects of human immunodeficiency virus

Abstract: 2'3,'-dideoxynucleosides which are effective in inhibiting the infectivity of the human immunodeficiency virus and which are stable in an acidic environment are disclosed, which compounds conform to the formula: (see fig. I) wherein X is selected from the group consisting of hydrogen, F, CN, N3 and NO2; Y is either H or F; with the proviso that Y is F only when X=H. Also disclosed is a compound of the formula: (see fig. II) Also disclosed are compounds conforming to the formula: (see fig. III) wherein R may be either OH or NH2; and L is NH2. Also disclosed are compounds conforming to the formula: (see fig. IV) wherein A is selected from the group consisting of OH and NH2; B is selected from the group consisting of H, CH3, CF3, CH=CHBr, and halogen.

Organoamidometallics. II. Decarboxylation Syntheses and Structures of [N,N-Dimethyl-N'-(Polyfluorophenyl)Ethane-1,2-Diaminato(1-)]Platinum(II) Complexes

Abstract: The complexes Pt[N(p-HC6F4)CH2CH2NMe2]X(L) (L = py , X = Cl or Br; L = 2- methylpyridine or 4-methylpyridine, X = Cl ) have been prepared by decarboxylation reactions between PtX2( dmen ) ( dmen = N,N- dimethylethane - 1,2-diamine) and thallous pentafluorobenzoate in the appropriate hot pyridine. Other organoamidoplatinum (II) complexes, Pt[N(R)CH2CH2NMe2] X( py ) (R = p-HC6F4, X = I; R = C6F5, X = Cl , Br or I; R = p-MeC6F4, X = Cl ; R = p-ClC6F4 or p-BrC6F4, X = I) and Pt[N(R)CH2CH2NMe2] Cl ( dmpy ) (R = p-HC6F4; dmpy = 2,5-dimethylpyridine), have been prepared by analogous decarboxylations between PtX2( dmen ), thallous 2,3,5,6- tetrafluorobenzoate, and the corresponding polyfluorobenzene, RF. The mixed halogen complex Pt[N(C6F5)CH2CH2NMe2]I0.63Cl0.37( py ) has been prepared similarly and the crystal structure determined. This shows square-planar stereochemistry with the halogen and pyridine trans to NC6F5 and NMe2 respectively. Comparison of spectroscopic data suggests the other complexes have similar stereochemistry.

Improvements in the chemical generation of chlorine and bromine, and their respective hydrides as a means of sample introduction into an atmospheric pressure helium microwave-induced plasma

Abstract: Chlorine and bromine, and their respective hydrides have been generated chemically from aqueous solution with a variety of reagents. The emission from the analytes was monitored at the following spectral lines: Cl II 479.455 nm and Br II 470.485 nm. Detection limits for the Cl2, HCl, Br2 and HBr generations were 0.6 ng of Cl, 0.3 ng of Cl, 0.09 ng of Br and 1.2 ng of Br, respectively, for aqueous solutions.

Method for removing organic and/or inorganic films by dry plasma ashing

Abstract: A method and apparatus for removing organic and/or inorganic film by dry plasma ashing, in which a first gas containing halogen element and a second gas containing a water vapor gas, at least a hydrogen element or at least an oxygen element are introduced into a reaction chamber (21) containing a material (22) to be treated therein

Bisphenylalkylpiperazine derivatives, a method of their preparation and a pharmaceutical preparation

Abstract: The present invention concerns novel compounds of formula (I), wherein R1 and R2 are the same or different and selected from hydrogen and halogen; R3 and R4 are the same or different and selected from hydrogen and lower alkyl; n is 2 or 3; A is selected from the pyrimidyl or pyridyl groups (a), (b), (c), (d), wherein R5 is selected from hydrogen, lower alkyl or halogen; R6 and R7 are the same or different and selected from hydrogen, halogen, lower alkyl, electron donor groups such as lower alkoxy or hydroxy, electron acceptor groups such as cyano, nitro, trifluoromethyl, COOR8, CONR9R10 or CO-B; wherein R8 is hydrogen or lower alkyl; R9 and R10 are the same or different and selected from hydrogen, lower alkyl and cycloalkyl; B is selected from (e), (f), wherein m is 1, 2, 3 or 4. R11 is selected from hydrogen or lower alkyl, and the pharmacologically active salts thereof. The new compounds can be used for treating mental disorders.

Method for preparing basic aluminum halides by reacting aluminum halide with aluminum

Abstract: Polymeric basic aluminum halides having the empirical formula: Al.sub.2 (OH).sub.6-y X.sub.y where X is chlorine, bromine or iodine, y has a numerical value from 0.7 to 3, and whose polymer distribution as characterized by size exclusion chromatography is: (a) 100% of the polymers are found in Bands II, III and IV, and (b) Band III contains at least 25% of the polymer; are obtained by heating aluminum metal with AlX 3 .6H 2 O in water, where X is halogen.

Silver fluoride supported on calcium fluoride. Improved fluorination and halofluorination reactions.

Abstract: Silver fluoride dispersed on the surface of calcium fluoride shows improved fluoride nucleophilicity for halogen exchange and addition to alkenes.

Imidazo(2,1-b)benzothiazoles and their acid addition salts, process and intermediates for their preparation, their use as medicaments and pharmaceutical compositions containing them

Abstract: Compounds of formula: … … in which R1 denotes either the group (A): … … in which R4 and R5 are hydrogen or C1-5 alkyl, R6 is hydrogen, C1-5 alkyl, phenyl, halogen, C2-5 alkoxycarbonyl, cyano, amido, mono- or dialkylamido, or the group (B): … … in which R7 and R8 are hydrogen, C1-5 alkyl, R2 and R3 denote: … … in which m is 1, 2 or 3, X1 and X2 are hydrogen, alkyl, alkenyl, C5 alkoxy, aralkoxy, aryloxy, halogen, nitrile or azido or X1 and X2 together form a methylenedioxy radical, and their salts, their preparation, their application as medications and new intermediates.

Anti-ulcerative imidazopyridine compounds

Abstract: The invention relates to an imidazopyridine compound of the following formula: ##STR1## wherein R1 is lower alkynyl, R2 is lower alkyl, R3 is lower alkyl, R4 is amino or acylamino, R5 is hydrogen; lower alkyl which may be substituted by halogen, halogen; nitro; amino; acylamino; esterified carboxy; or N,N-di(lower)alkylsufamoyl, and A is lower alkylene, and pharmaceutically acceptable salts thereof, useful in the treatment of ulcers.

Chemical decomposition of chlorofluorocarbons by reductive dehalogenation using sodium naphthalenide

Abstract: All halogen atoms in 1,1,2-trichloro-1,2,2-trifluoroethane (F-113) were removed in the form of chloride and fluoride ions by the treatment with sodium naphthalenide (1.5 equiv. per halogen atom) in THF at 150 °C for 50 min in the presence of 10 vol% tetraethyleneglycol dimethylether. Similar treatment was also efficacious in the dehalogenation of F-22 and F-12.

2,5-Dihydropyrroles

Abstract: Herbicidally active novel 2,5-dihydropyrroles of the formula ##STR1## wherein R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 and R3 each represent an alkyl group having 1 to 4 carbon atoms or a haloalkyl group having 1 to 4 carbon atoms or together may form a C2 -C6 alkylene group which may be substituted by halogen, and R represents a hydroxy group, a mercapto group, a halogen atom, an amino group or a group of the formula --O--W in which W represents an alkylcarbonyl, a halogenoalkylcarbonyl, an alkoxycarbonyl or a halogenoalkoxycarbonyl group each having 1 to 4 carbon atoms in the alkyl group, an alkylsulfonyl or a halogenoalkylsulfonyl group each having 1 to 4 carbon atoms in the alkyl group or a di-C1 -C4 -alkylamino sulfonyl group.

Reductive dehalogenation of organic halogen compounds

Abstract: Organic halogen compounds in which one or more halogen atoms are covalently bonded to the carbon are subjected to reductive dehalogenation by reaction with a hydrocarbon in the presence of carbon at elevated temperatures with formation of a hydrogen halide, by a process in which the dehalogenation is carried out in the presence of iron powder or an iron compound as a cocatalyst, at from 100° to 450° C.

Quinoline carboxylic acid boric acid anhydrides and process for the preparation thereof

Abstract: The invention relates to new quinoline-3-carboxylic acid anhydrides of general formula (I) (wherein R stands for cyclopropyl, a group of the general formula -CH2CR5R6r7 (wherein R5, R6 and R7 stand for hydrogen or halogen), or phenyl optionally substituted by 1 or 2 halogen, R1 and R2 stand for halogen, or an aliphatic acyloxy group containing 2 to 6 carbon atoms optionally substituted by halogen, or an aromatic acyloxy group containing 7 to 11 carbon atoms, R3 stands for chlorine or fluorine and R4 stands for hydrogen or fluorine) and to the process for the preparation thereof which comprises reacting a compound of general formula (II), (wherein R, R3 and R4 are the same as stated above, R8 stands for hydrogen or alkyl containing 1 to 4 carbon atoms) with a compound of the formula (III): HBF4, or a borone derivative of the general formula (IV): BX3 (wherein X stands for fluorine, chlorine or bromine) or an ether complex thereof, or a triacyloxy borate derivative of the general formula (V): -B(OCOR9)3 (wherein R9 stands for alkyl containing 1 to 5 carbon atoms optionally substituted by halogen, or aryl containing 6 to 10 carbon atoms). The compounds of general formula (I) are new intermediates for the preparation of known quinoline-3-carboxylic acids showing antibacterial activity.