Showing papers on "Halogen published in 1971"

The Fluorine, Chlorine, Bromine, and Iodine Contents of Volcanic Rocks in Japan

Abstract: The halogen contents of 49 Japanese volcanic rocks are; F: 50–1700 (average 410), Cl: 17–1220 (av. 270), Br: 0.09–8.10 (av. 0.85), I: 0.011–0.32 (av. 0.088) μg/g. The fluorine and chlorine were determined by usual photometric methods, and the bromine and iodine, by photometric methods based on their catalytic action, after decomposition and separation procedures suitable for each case. The bromine and iodine contents are appreciably lower than the values generally accepted for igneous rocks. The bromine content agrees with Sugiura’s value. The frequency distribution of each halogen content shows an approximate lognormality. The chlorine and bromine contents are strongly correlated, and the Br/Cl atomic ratio is in a narrow range (0.66–3.7)×10−3 (av. 1.5×10−3). No other correlation is observed among the halogen contents at all. Each halogen content has no marked relation to the type of rock. A regional difference is seen in the F/Cl and I/Br ratios. Three ultrabasic rocks have very low fluorine (≤20) and c...

Oxidative hair dye compositions

Abstract: Oxidative hair dye composition containing as ''''para component'''' compounds of the formula: OR THEIR ACID ADDITION SALTS, IN WHICH: R1 is alkyl or hydroxyalkyl; R2 is hydrogen or hydroxyalkyl; R3 is hydrogen, alkyl, alkoxy or halogen; and R4 occupies any one of the remaining positions ON THE BENZENE RADICAL AND IS HYDROGEN, ALKYL, ALKOXY OR HALOGEN; PROVIDING THAT R2 is hydrogen when R3 is alkyl, alkoxy or halogen and providing that at least two of R1, R2, R3 or R4 are other than hydrogen

Diacrylate esters of low viscosity and the use thereof as binders in dental restorative compositions

Abstract: COMPOUNDS OF THE FORMULA: CH2=C(-R1)-COO-R-OOC-C(-R1)=CH2 WHEREIN R IS SELECTED FROM (CYCLOHEXYL)2-C(-CH3)2, -CH2-(1,4-CYCLOHEXYLENE)-CH2-, -CH2-(1,4-PHENYLENE)-O-(1,4-PHENYLENE)-CH2-, AND -CH2-(1,4-PHENYLENE)-CH2- AND R1 IS HYDROGEN, LOWER ALKYL, OR HALOGEN, ARE UTILIZED AS BINDERS IN DENTAL RESTORATIVE COMPOSITIONS. THE COMPOUNDS ARE PREPARED BY THE REACTION OF AN ACRYL CHLORIDE AND DERIVATIVES THEREOF WITH THE APPROPRIATE DIOL.

4(1-alkyl-4-piperidylidine)-4h-benzo {84,5{9 {0 cyclohepta {8 1,2{14 6{9

Abstract: The present invention concerns novel compounds of the formula, WHEREIN R1 is hydrogen, halogen, or alkoxy of one to four carbon atoms, R2 is alkyl of one to four carbon atoms, and -A-B- is -CO-CH2-CO- or -CO-CH2-, and pharmaceutically acceptable acid addition salts thereof. The compounds are histaminolytics. Compounds wherein -A-B- is CO-CH2- are antaminics, i.e. aside from histaminolytic properties, they possess serotonin - antagonistic and anticholinergic properties.

Purification of carboxylic acids

Abstract: A PROCESS FOR THE REMOVAL OF HALOGEN CONTAMINANTS AND THE DRYING OF AQUEOUS MONOCARBOXYLIC A ACIDS, PARTICULARLY THOSE PRODUCED BY THE REACTION OF AN ALCOHOL OR OLEFIN AND CARBON MONOXIDE IN THE PRESENCE OF THE CATALYTIC SYSTEM COMPRISING A GROUP VIII METAL COMPONENT AND A HALOGEN COMPONENT CONTAINING BROMINE OR IODINE AND AT LEAST A PORTION OF THE HALOGEN COMPONENT BEING EITHER AN ALKYL HALIDE AND/OR A HYDROGEN HALIDE. THE PROCESS COMPRISES INTRODUCING A MONACARBOXYLIC ACID STREAM CONTAINING WATER AND THE HALOGEN CONTAMINANT INTO THE UPPER HALF OF A DISTILLATION COLUMN, REMOVING AN OVERHEAD FRACTION CONSISTING PRIMARILY OF THE WATER AND ALKYL HALIDE CHARGE TO SAID COLUMN, REMOVING A STREAM FROM THE MIDDLE PORTION OF SAID COLUMN CONTAINING A MINOR PROPORTION OF HYDROGEN HALIDE PRESENT IN SAID COLUMN, AND REMOVING A PRODUCT ACID STREAM FROM AT OR NEAR THE BOTTOM OF SAID COLUMN, THE PRODUCT ACID STREAM BEING ESSENTIALLY DRY AND SUBSTANTIALLY FREE OF THE HALOGEN CONTAMINANTS CHARGED TO SAID COLUMN. THE METHOD IS PARTICULARLY APPLICABLE TO THE REMOVAL OF WATER AND IODINE-CONTAINING COMPOUNDS FROM ACETIC AND PROPIONIC ACIDS.

Measurements of Chemical Shifts in the Photoelectron Spectra of Arsenic and Bromine Compounds

Abstract: Chemical shifts in the binding energies of electrons in 3d orbitals of bromine and arsenic have been measured by photoelectron spectroscopy, using soft x rays. The bromine salts studied were KBr, KBrO3, and KBrO4; the results are compared to corresponding chlorine and iodine salts studied by other workers. For a given increase in oxidation number, the shift (increase) in binding energy of bromine is intermediate to those for chlorine and iodine, chlorine shifts are higher, and iodine shifts are lower. This trend can be qualitatively explained by Hartree–Fock calculations of differences in binding energies for free halogen ions. Chemical shifts for arsenic can be correlated to variations in the effective charges on arsenic caused by different chemical environments. Calculations of the charge were made by considering the partial ionic character of bonds. A demonstration that photoelectron spectroscopy can be used in arsenic pollution problems has been made.

Process for the isomerization of hydrocarbons

Abstract: PARAFFINIC AND/OR ALKYL SUBSTITUTED AROMATIC HYDROCARBONS ARE ISOMERIZED WITH A CATALYST COMPRISING (A) A LEWIS ACID OF THE FORMULA MXN WHERE M IS SELECTED FROM GROUP IV-B, V OR VI-B OF THE PERIODIC TABLE, X IS A HALOGEN AND N VARIES FROM 3 TO 6, AND (B) A STRONG BRONSTED ACID COMPRISING FLUOROSULFURIC ACID, TRIFLUORO- METHANESULFONIC ACID, TRIFLUOROACETIC ACID OR MIXTURES THEREOF.

Organic fluorine chemistry

Abstract: 1. Introduction.- Development of Fluorine Chemistry.- Handling of Fluorine, Hydrogen Fluoride, and Fluorine Compounds.- Equipment and Apparatus.- 2. Fluorinating Agents.- Hydrogen Fluoride.- Fluorine.- Inorganic Fluorides.- Organic Fluorides.- 3. Nomenclature of Organic Fluorine Compounds.- 4. Introduction of Fluorine into Organic Compounds.- Addition of Hydrogen Fluoride to Olefins.- Addition of Hydrogen Fluoride to Acetylenes and Other Unsaturated Systems.- Addition of Fluorine to Olefins.- Addition of Fluorine to Other Unsaturated Systems.- Addition of Halogen Fluorides and Organic Fluorides to Olefins.- Replacement of Hydrogen by Fluorine.- Replacement of Halogens by Fluoride.- Replacement by Means of Hydrogen Fluoride.- Replacement by Means of Antimony Fluorides.- Replacement by Means of Silver Fluoride.- Replacement by Means of Mercury Fluorides.- Replacement by Means of Potassium Fluoride.- Replacement by Means of Other Fluorides.- Replacement of Oxygen by Fluorine.- Cleavage of Ethers and Epoxides.- Cleavage of Sulfonic Esters.- Replacement of Hydroxylic Group by Fluorine.- Replacement of Carbonyl Oxygen by Fluorine.- Conversion of Carboxylic Group to Trifluoromethyl Group.- Replacement of Nitrogen by Fluorine.- 5. Analysis of Organic Fluorine Compounds.- Physical Methods of Analysis of Fluorine Compounds or Their Mixtures.- Infrared Spectroscopy.- Mass Spectroscopy.- Nuclear Magnetic Resonance Spectroscopy.- Separation of Mixtures and Purification of Components.- Qualitative Tests for Fluorine.- Detection of Elemental Fluorine.- Detection of Fluoride Ion.- Detection of Fluorine in Organic Compounds.- Quantitative Determination of Fluoride.- Volumetric Determination.- Determination Using Fluoride Membrane Electrode.- Mineralization of Fluorine in Organic Compounds.- Decomposition with Alkalies.- Combustion in Oxygen.- Determination of Other Elements in Organic Fluorine Compounds.- Special Analyses.- 6. Properties of Organic Fluorine Compounds.- Physical Properties.- Melting Points.- Boiling Points.- Density.- Refractive Index.- Dielectric Constant.- Surface Tension.- Viscosity.- Solubility.- Physicochemical Properties.- Biological Properties.- 7. Practical Applications of Organic Fluorine Compounds.- Refrigerants, Propellants, and Fire Extinguishers.- Plastics and Elastomers.- Monomers.- Polymerization.- Processing of Polymers.- Applications of Plastics and Elastomers.- Fluorinated Compounds as Pharmaceuticals.- Other Uses of Fluorinated Compounds.- 8. Reactions of Organic Fluorine Compounds.- Factors Governing the Reactivity of Organic Fluorine Compounds.- Inductive Effect.- Hyperconjugation.- Mesomeric Effect.- Steric Effects.- Important Features in the Reactivity of Organic Fluorine Compounds.- Reduction.- Catalytic Hydrogenation.- Reduction with Complex Hydrides.- Reduction with Metals and Metallic Compounds.- Reduction with Organic Compounds.- Oxidation.- Oxidations with Oxygen.- Oxidations with Oxidative Reagents.- Oxidations of Fluoro-olefins.- Oxidations of Fluorinated Aromatics.- Oxidation of Nitrogen and Sulfur Compounds.- Anodic Oxidation.- Electrophilic Reactions.- Halogenation.- Addition of Halogens across Multiple Bonds.- Replacement of Hydrogen by Halogens.- Cleavage of the Carbon Chain by Halogens.- Addition of Hydrogen Halides across Multiple Bonds.- Replacement of Oxygen- and Nitrogen-Containing Functions by Halogens.- Replacement of Fluorine by Other Halogens.- Nitration.- Nitrosation.- Sulfonation.- Acid-Catalyzed Syntheses (Friedel-Crafts Reaction).- Acid-Catalyzed Additions.- Acid-Catalyzed Substitutions.- Nucleophilic Substitutions.- Esterification and Acetalization.- Hydrolysis.- Hydrolysis of Nonfluorinated Parts of Fluorinated Molecules.- Hydrolytic Displacement of Single Fluorine Atoms.- Hydrolysis of Difluoromethylene Group.- Hydrolysis of Trifluoromethyl Group.- Hydrolysis of Perfluoro Compounds.- Fluoroform Reaction.- Alkylations.- Alkylations at Oxygen.- Alkylations at Sulfur.- Alkylations at Nitrogen and Phosphorus.- Alkylations at Carbon.- Arylations.- Arylations at Oxygen.- Arylations at Sulfur.- Arylations at Nitrogen.- Arylations at Carbon.- Acylations.- Acylations at Oxygen.- Acylations at Sulfur.- Acylations at Nitrogen.- Acylations at Carbon.- Syntheses with Organometallic Compounds.- The Grignard Syntheses.- Grignard Reagents as Organic Substrate.- Fluorinated Grignard Reagents.- Perfluorinated Grignard Reagents.- Organolithium Compounds.- Organolithium Compounds as Organic Substrate.- Fluorinated Organolithium Compounds.- Perfluorinated Organolithium Compounds.- Organozinc Compounds.- Organomercury Compounds.- Organocopper Compounds.- Organometalloids.- Base-Catalyzed Condensations.- Additions.- Nucleophilic Additions to Fluorinated Olefins.- Additions of Alcohols and Phenols.- Additions of Mercaptans and Thiophenols.- Additions of Ammonia and Amines.- Free-Radical-Type Additions.- Linear Additions.- Cycloadditions.- Formation of Three-Membered Rings.- Formation of Four-Membered Rings.- Formation of Five-Membered Rings.- Formation of Six-Membered Rings (Diels-Alder Reaction).- Eliminations.- Dehalogenations.- Dehydrohalogenations.- Decarboxylations.- Dehydration.- Molecular Rearrangements.- Pyroreactions.- 9. Fluorinated Compounds as Chemical Reagents.- References.- Author Index.

Process for hydrocracking heavy hydrocarbons

Abstract: There is disclosed a process for hydrocracking coal or other heavy hydrocarbon fractions employing a molten catalyst system, including a mineral acid that is stable at reaction conditions, and a metal halide catalyst selected from zinc chloride, bromide or iodide, antimony bromide or iodide, tin bromide, titanium iodide, arsenic bromide or iodide, mercuric bromide or iodide, gallium bromide, or bismuth bromide. If a halogen acid is employed as the mineral acid, it is preferred that the halogen in the metal salt correspond to the halogen in the acid.

Silyl and germyl compounds of platinum and palladium. Part I. Platinum derivatives of monosilane and monogermane

Abstract: Reactions of trans-XP(PEt3)2H with MH4–nXn(M = Si or Ge; X = Cl, Br, I; n= 0–3) in benzene at room temperature give trans-XPt(PEt3)2MH3–nXn; with MH3Y (Y = F, Cl, Br, I) halogen exchange leads to the formation of that product in which the heavier halogen is bound to Pt. Oxidative addition of MH3X to trans-(Et3P)2Ptl2 gives (Et3P)2Pt(MH2X)(H)I2, which slowly decomposes at room temperature to give H2 and trans-IPt(PEt3)2MHXI. Reaction of MH4 or of MH3Cl with trans-(Et3P)2PtCl2 is much slower and no product containing 6-coordinate Pt was detected. The mechanisms of these reactions and of the reactions of trans-CIPt(PEt3)2MH2Cl with hydrogen chloride are discussed; vibrational and 1H n.m.r. spectra of the platinum complexes are described. Reactions of trans-CIPt(PEt3)2SiH2Cl with methanol and with water are complicated; with dimethylamine, trans-CIPt(PEt3)2SiH2NMe2 is formed. Reactions of trans-CIPt(PEt3)2SiH2Cl with Et3P, with Me3N, with PH3, with Mel, with hexene, and with ethylene have been investigated.

High ignition temperature polymers substituted with halogen substituted aromatic groups

Abstract: HIGH IGNITION TEMPERATURE AROMATIC CARBONATE POLYMERS DERIVED FROM DIHYDRIC PHENOLS CONTAINING TERMINAL BROMINE SUBSTITUTED AROMATIC GROUP AND CONTAIN 3-5 HALOGEN ATOMS THE POLYMERS ARE PREPARED BY REACTING BISPHENOLA, PHOSGENE AND PENTABROMOPHENOL, FOR EXAMPLE

The reaction of hydrazones with chlorine and bromine

Abstract: The reactions of six hydrazones with bromine in the presence of pyridine, and of two hydrazones with chlorine under a variety of conditions, were investigated. Geminal dihalides, haloalkenes, rearranged products, azines, and carbonyl compounds account for up to 85% of the products of the reaction with bromine, but the reactions with chlorine give rise to more complex mixtures. The mechanisms of these reactions are discussed and compared with the analogous reactions with iodine. The differences in the distribution of products for different halogens and bases can be rationalized in terms of competing a-eliminations and nucleophilic substitutions of common intermediate X-halogeno compounds. However, the reaction with chlorine is not entirely straightforward. Further evidence is presented for the intermediacy of halocarbonium ions in the reactions of hydrazones with halogens in the presence of bases.

The vibrational spectra and structure of the Bis(hexamethylenetetramine)iodine(I) cation

Abstract: The crystalline compound reported in the literature as the 1 : 1 addition complex of hexamethylenetetramine (hx) with iodine is shown by means of i.r. and Raman spectroscopy to be an ionic compound consisting of bis(hexamethyl-enetetramine)iodine(I) ions, (hx)2I+, and I3- ions. A crystalline compound consisting of molecules of the true 1 : 1 addition complex (hx)I2 does exist, however, and its preparation is described. On standing, this compound undergoes an unusual solid state transformation, resulting in the formation of the ionic complex. The (hx)2I+ ion is the first documented example of a bis(amine)halogen(I) ion involving an amine other than pyridine or its derivatives. A structure for this ion is proposed in which the hexamethylenetetramine molecules are bound to the iodine atom through one of their nitrogen atoms, the resulting N...I...N arrangement being linear, centrosymmetric, and lying along the threefold axis passing through the coordinated nitrogen atom of each hexamethylenetetramine molecule. The evidence for this structure obtainable from the vibrational spectra of the ion is discussed. A preliminary investigation of the valence force field indicates unusually strong nitrogen-iodine bonding in this ion. The literature method for preparing bis-(pyridine)halogen(I) perchlorates has been modified and used to prepare the perchlorate of bis(hexamethylenetetramine)iodine(I).

Infrared spectroscopic studies of adsorption on alkali halide surfaces I. HCl, HBr and HI on fluorides, chlorides, bromides and iodides

Abstract: An infrared spectroscopic study of the adsorption of hydrogen halides HCl, HBr, and HI on alkali-metal chlorides, bromides and iodides has shown the presence of a dominant surface species involving hydrogen bonding between the hydrogen halide molecule and a surface anion In favourable cases it has been possible to measure all three vibration frequencies of the surface complex X- H Y - (X and Y halogen atoms) in the infrared and far infrared regions HCl forms hydrogen bonds of increasing strength with the surface along the sequences LiCl v (HCl) vibrations In the presence of adsorbed water additional bands in the regions of 2100 and 1200 cm -1 have been tentatively interpreted in terms of protonated surface anions Mixed halogen systems gave anomalous spectroscopic results when the halogen of the hydrogen halide occurs further down the Periodic Table than the halogen of the salt These have been satisfactorily interpreted in terms of surface halogen exchange reactions of the type Br— H + Cl - (surface) -> Cl— H Br - (surface) Adsorption of hydrogen chloride and deuterium chloride on lithium, sodium, potassium and caesium fluorides gives rise to very different infrared spectra originating in the bifluorideion [FHF] - Closely similar spectra are obtained from hydrogen bromide on sodium fluoride, and exploratory spectra were obtained from HCl on calcium fluoride The first step in the production of this species may be the halogen exchange reaction XH + F - → X - + HF, where (X = Cl, Br) The absorption bands from the [FHF] - surface species have very considerable breadths which are independent of surface coverage over a wide range This phenomenon seems most satisfactorily interpreted in terms of interactions between adjacent [FHF] - ions in islands resulting from the corrosive reaction between the hydrogen halide and the fluoride surface about active centres

3,4,5-tri-substituted cinnamides

Abstract: COVERS COMPOUND OF THE FORMULA: 1,3-DI(Y-),2-X,5-(D-CO-CH=CH-)BENZENE WHERE X IS SELECTED FROM THE GROUP CONSISTING OF NH2, NH-LOWERALKYL AND N(LOWERALKYL)2; EACH Y IS A HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE, FLUORINE AND IODINE; AND D IS AN ORGANIC RADICAL CONTAINING A NITROGEN ATOM; AND PHARMACEUTICALLY-ACCEPTABLE ADDITION SALTS THEREOF. ALSO COVERS THEIR USE AS ANTI-DEPRESSANT DRUGS. IN ADDITION COVERS VARIOUS NOVEL INTERMEDIATES USED IN PREPARING THE ABOVE COMPOUNDS.

The standard potentials of silver–silver halide electrodes and ion solvation in dimethyl sulphoxide–water mixtures at 25 °C

Abstract: Standard e.m.f.s of the cells H2|HX|AgX–Ag (X = Cl, Br, or I) in 10, 60, 70, and 80%(w/w) dimethyl sulphoxide–water mixtures are reported. These, together with values for mixtures of other compositions determined earlier, were used to calculate the molar free energies of transfer of the halogen acids from water to the mixed solvents. Single-ion values were derived therefrom by use of the extrathermodynamic assumptions of Feakins et al. and discussed in terms of ion solvation. It is shown that the solvophilicity of the ions is largely determined by their acid–base' interactions with the solvent molecules. The structural features of the solvents are briefly discussed.

The microgasometric determination of some inorganic and organic nitrates by reduction with iodide ion and elemental iodine

Abstract: Simple micro methods are described for the determination of nitrate based on its reduction with iodide or iodine in the presence of halogen acids. Nitric oxide gas is liberated and iodine(I) is the oxidation product from both iodide and iodine.

An electron resonance study of some reactions involving silyl radicals

Abstract: Specific alkyl radicals for e.s.r. studies can be prepared conveniently in the cavity of an e.s.r. spectrometer by photolysis of a mixture of the appropriate alkyl bromide (or chloride) with triethylsilane and t-butyl peroxide. The triethylsilyl radical, produced as an intermediate, will abstract chlorine or bromine from alkyl halides, but abstraction of fluorine has not been observed. Although ketones and esters react with triethylsilyl radicals by addition to the oxygen atom of the carbonyl group, halogeno-ketones and halogeno-esters react preferentially by abstraction of the halogen atom. Bromobenzene, 1-bromohex-1-yne, and cyclopropyl bromide do not give e.s.r. spectra corresponding to the organic radicals: it appears that these reactive radicals react further with triethylsilane to give the observed Et2SiHĊHCH3 radical, but the cyclopropyl radical could be detected when trimethylsilane was used instead of triethylsilane in the reaction mixture. Competition experiments show that ease of removal of halogen atoms increases in the order primary alkyl < secondary < tertiary < acetonyl ≈·CH2·CO2Et < allyl ≈ propargyl ≈ benzyl < cyanomethyl.

The Solvent Effect on the Reaction of 1,1,4,4-Tetraphenyl-2-halobuta-2,3-dien-1-ol with Mercuric Halide

Abstract: The reaction of the title compound (I) with mercuric halide in an aprotic and in a protic solvent afforded the fulvene derivative (VII) and the dihydrofuran derivative (VIII or IX) respectively. Both the cross-reactions (bromo-analog of I (Ia)+HgCl2, chloro-analog of I (Ib)+HgBr2) in an aprotic solvent afforded the chloro-fulvene derivative (VIIb). However, when the above reactions were carried out in a protic solvent, the product was the dihydrofuran derivative (IX), in which the halogen combining with carbon is chlorine and that combining with mercury is bromine. On the basis of the results of those cross-reactions, the reaction mechanism will be discussed. Acetonitrile showed distinctive behavior. In acetonitrile, the bromine of Ia was easily exchanged with the chlorine of sodium chloride at room temperature, and Ib was obtained quantitatively.

Light-sensitive silver halide photographic material with sensitizing dye combination

Abstract: Photographic materials of improved green sensitivity are described containing a light-sensitive silver halide emulsion and including, in combination, at least one monomethinecyanine dye of the general formula, Wherein Y2 is a hydrogen atom or a lower alkyl group; Y3 is a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a halogen atom or a phenyl group; W is a halogen atom or a phenyl group; R3 is a lower alkyl group; M is a hydrogen atom, an alkali metal atom or H.Q (where Q is an organic base); and n1 and n2 are individually 2, 3 or 4. Lower fog levels are also noted. Emulsions are detailed as well as materials utilizing such emulsions. WHEREIN Y1 is a hydrogen atom, a lower alkyl group or a lower alkoxy group; Z is S or Se; V is a hydrogen atom or a lower alkyl group; R1 is a lower alkyl group or a substituted alkyl group; R2 is a sulfoalkyl group or a carboxyalkyl group; X is an anion; and m is zero or 1, and at least one oxacarbocyanine dye of the general formula, D R A W I N G

Acetylenic derivatives of zinc

Abstract: SOLUTIONS OF ORGANO-ZINC COMPOUNDS OF THE FORMULAE: X-ZN-C$CH AND X-ZN-C$C-NZ-X WHERE X IS HALOGEN, MADE BY REACTION OF AN ALKYL ZINC HALIDE WITH ACETYLENE, ARE USED FOR MAKING ACETYLENIC ORGANO-SILICON COMPOUNDS BY REACTION WITH COMPOUNDS CONTAINING SILICON-CHLORINE BONDS.

Nucleophilic heteroaromatic substitution. Part XXXIV. Fluorine versus chlorine mobility in reactions with methanolic methoxide ion and with piperidine in various solvents

Abstract: The rate constants and the activation parameters for the title reactions of some 2-halogenopyridines, 2- and 4-halogenoquinolines, and 2-halogenoquinoxalines are reported. The observed leaving-group effects on both rate constants, kF > kCl, and activation enthalpies, ΔHF‡ < ΔHCl‡, though analogous to those known for the similar reactions of nitro-activated aromatic compounds, reveal new features that characterise aza-activation. These include relatively low kF/kCl values for the piperidinodehalogenations in piperidine solution and a significant positional effect on the relative halogen mobility for the reactions with methoxide ion. The reaction mechanisms are discussed in the light of these observations and other previously reported facts. The results with the γ-fluoro-derivatives were made possible by the syntheses of previously unreported 4-fluoro-2,8-dimethyl- and 4-fluoro-2-methoxy-quinoline.