- TETRAHEDRAL INTERMEDIATES 4. THE EFFECT OF CHLORO-SUBSTITUENTS ON THE KINETICS OF THE BREAKDOWN OF HEMIORTHOESTERS
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2-Hydroxy-2-chloromethyl-1,3-dioxolane (4) and 2-hydroxy-2-dichloromethyl-1,3-dioxolane (5) have been detected as intermediates by 1H NMR spectroscopy in the hydration of respectively 2-chloromethylene-1,3-dioxolane and 2-dichloromethylene-1,3-dioxolane in aqueous acetonitrile.The kinetics of the breakdown of (4) and (5) into ethylene glycol monochloroacetate and monodichloroacetate have been studied by uv spectroscopy and values of kH(+), kHO(-), and kH2O evaluated.It was found that the introduction of chlorosubstituents into 2-hydroxy-2-methyl-1,3-dioxolane caused a decrease in kH(+) and increase in kHO(-) and little change in kH2O for its breakdown.The mechanisms of these reactions are discussed.
- Capon, Brian,Dosunmu, Miranda I.
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- In situ derivatization/solid-phase microextraction for the determination of haloacetic acids in water
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An in situ derivatization solid-phase microextraction method has been developed for the determination of haloacetic acids (HAAs) in water. The analytical procedure involves derivatization of HAAs to their methyl esters with dimethyl sulfate, headspace sampling using solid-phase microextraction (SPME), and gas chromatography-ion trap mass spectrometry (GC/ITMS) determination. Parameters affecting both derivatization efficiency and headspace SPME procedure, such as the selection of the SPME coating, derivatization-extraction time and temperature, and ionic strength, were optimized. The commercially available Carboxen-poly(dimethylsiloxane) (CAR-PDMS) fiber appears to be the most suitable for the determination of HAAs. Moreover, the formation of HAA methyl esters was dramatically improved (up to 90-fold) by the addition of tetrabutylammonium hydrogen sulfate (4.7 μmol) to the sample as ion-pairing agent in the derivatization step. The precision of the in situ derivatization/HS-SPME/GC/ITMS method evaluated using an internal standard gave relative standard deviations (RSDs) between 6.3 and 11.4%. The method was linear over 2 orders of magnitude, and detection limits were compound-dependent, but ranged from 10 to 450 ng/L. The method was compared with the EPA method 552.2 for the analysis of HAAs in various water samples, and good agreement was obtained. Consequently, in situ derivatization/HS-SPME/GC/ITMS is proposed for the analysis of HAAs in water.
- Sarrion,Santos,Galceran
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- Selective Photo-Oxygenation of Light Alkanes Using Iodine Oxides and Chloride
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Partial oxidation of light alkanes to generate alkyl esters has been achieved under photochemical conditions using mixtures of iodine oxides and chloride salts in trifluoroacetic acid (HTFA). The reactions are catalytic in chloride and are successful using compact fluorescent light, but higher yields are obtained using a mercury lamp. In this photo-initiated oxyesterification process, the robust alkyl ester products are resistant to over-oxidation, and under optimized conditions yields for alkyl ester production of ~50 % based on methane, ~60 % based on ethane (with a total functionalized yield of EtX (X=TFA or Cl) of 80 %) and ~30 % based on propane have been demonstrated. The reaction also proceeds in aqueous HTFA and dichloroacetic acid with lower yields. Mechanistic studies indicate that the process likely operates by a chlorine hydrogen atom abstraction pathway wherein alkyl radicals are generated, trapped by iodine, and converted to alkyl trifluoroacetates in situ.
- Liebov, Nichole S.,Goldberg, Jonathan M.,Boaz, Nicholas C.,Coutard, Nathan,Kalman, Steven E.,Zhuang, Thompson,Groves, John T.,Gunnoe, T. Brent
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p. 5045 - 5054
(2019/10/28)
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- Reactions of trialkyl phosphites with mono- and diacylals of halo-substituted acetic acids
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Trialkyl phosphites react with diacylals of di- and trichloroacetic acids by the pathway of the Perkow reaction; with monoacylals of bromo- and iodoacetic acids, by the pathway of the classical Arbuzov reaction; and with monoacylals of di- and trichloroacetic acids, by the pathway of the nonclassical Arbuzov reaction.
- Gazizov,Gaisin,Khairullin,Safina,Karimova,Petrova
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p. 1738 - 1741
(2007/10/03)
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- Reformatsky-type addition of esters of α-halogeno carboxylic acids to aldehydes and ketones in the presence of Fe(CO)5
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Reformatsky-type addition of esters of α-halogeno carboxylic acids to aldehydes and ketones in the presence of Fe(CO)5 and an activating agent (CBrCl3 or I2) afforded the corresponding esters of β-hydroxy acids in good yields. Possible reaction mechanisms are discussed.
- Terent'ev,Vasil'eva,Kuz'mina,Mysov,Ikonnikov,Kuznetsov,Belokon'
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p. 1121 - 1127
(2007/10/03)
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- Intramolecular Geminal and Vicinal Element Effects in Substitution of Simple Bromo(chloro)alkenes by Methoxide and Thiolate Ions. An Example of a Single Step Substitution?
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Intramolecular element effects kBr/kCl for substitution of geminal bromochloroalkenes BrC(Cl)=C-(Br)Cl (1), BrC(Cl)=CCl2 (2), Me2C=C(Br)Cl (3), and XCH=C(Br)Cl (X = Cl, 4; X = Br, 5), with MeO- and RS- nucleophiles were investigated. 3 did not give substitution, and 4 and 5 gave substitution with MeO- via an initial elimination (to acetylene)-addition route, followed by further reactions. In reactions of 4 with thiolates, geminal element effects of 2-10 were obtained. Formation of RSC(Cl)=C(Cl)Y, Y = SR, Br, is ascribed to an initial halophilic reaction, followed by addition of RSCl to the formed acetylene. Reaction of 2 with MeO- gave a high vicinal element effect, and RS- gave a high geminal element effect. Reaction of 1 with both MeO- and RS- ions gave high (2 orders of magnitude) geminal element effects, which were interpreted as indicating a rate-determining C-X bond cleavage. This is supported by the high kBr/kCl intermolecular element effects (k(1)/k(Cl2C=CCl2) with MeO- and PhCH2S- ions. Mechanistic alternatives based on these observations are discussed.
- Beit-Yannai, Michal,Rappoport, Zvi,Shainyan, Bagrat A.,Danilevich, Yuri S.
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p. 8049 - 8057
(2007/10/03)
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- Process for the reaction of a low-molecular hydroxyl compound with a carboxylic acid halide
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In a process for reacting a low molecular weight hydroxy compound with a carboxylic acid halide, a small amount of the acid halide is introduced into the reaction vessel and the remainder of the acid halide and the hydroxy compound are added gradually in an approximately stoichiometric ratio. The hydrogen halide formed is thus prevented from dissolving in the reaction medium. The heat of reaction to be dissipated is negligible.
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- NUCLEOPHILIC REACTIONS AT A VINYLIC CENTER. XXVIII. FLUOROCHLOROETHENES AND FLUOROBROMOETHENES IN REACTIONS WITH SODIUM ALCOHOLATES AND ARENETHIOLATES
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During the reaction of halogenoethenes (Z+E)-CHX=CFX with sodium methoxide and with sodium p-thiocresolate in methanol initial attack by the nucleophilic takes place at the carbon atom attached to the fluorine atom.In the reactions with sodium methoxide the intermediate monosubstitution products are more reactive than the initial halogenoethenes, and the main reaction products are the ortho esters CHXYC(OMe)3.An "element effect", i.e., concurrent substitution of F and Cl(Br) in the reaction with sodium methoxide, was discovered.With sodium p-thiocresolate trifluorochloroethene gives the product from substitution of the chlorine atom and a small amount of the addition product as impurity.The other ethenes give substitution, addition, and halogenophilic reduction products and also the products from further transformations (hydrolysis and decarboxylation).
- Shainyan, B. A.,Vereshchagin, A. L.
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p. 1981 - 1988
(2007/10/02)
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- REACTION OF 1-(ACYLCARBAMOYL)-3,5,5-TRIMETHYL-2-PYRAZOLINES WITH NUCLEOPHILIC REAGENTS
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1-(Acylcarbamoyl)-3,5,5-trimethyl-2-pyrazolines react with water and alcohols to form 3,5,5-trimethyl-4,5-dihydro-1H-pyrazole-1-carboxamide with the elimination of substituted carboxylic acids. 1-(Benzoylcarbamoyl)-3,5,5-trimethyl-2-pyrazoline and 3,5,5-trimethyl-4,5-dihydro-1H-pyrazole-1-carboxamide form 2:1 complexes with Cu(II) ions.
- Zobova, N. N.,Nazyrova, A. Z.
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p. 1906 - 1908
(2007/10/02)
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- Ozonides of Acyclic Olefins Having Mono- and Dichloro-Substituted Double Bonds
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Ozonolyses of acyclic olefins containing 1,2-dichloro-substituted (4a,b) and monochloro-substituted double bonds (7a, b, 12) as well as two (4a, b, 7a, b) or one halomethyl group (12) attached to the double bond afford the corresponding ozonides as the first representatives of monocyclic chlorinated ozonides.Their stability decreases in order 5a, 5b > 8a, 8b > 13. - Key Words: Ozonides/ 1,2,4-Trioxolanes, 3-chloro-, 3,5-dichloro- / Polyethylene
- Griesbaum, Karl,Schlindwein, Konrad,Hilss, Michael
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p. 1843 - 1848
(2007/10/02)
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- INSERTION OF CARBENES INTO P-H BONDS. 5. SYNTHESIS OF NEW PHOSPHONATES AND PHOSPHINATES IN REACTIONS CATALYSED BY Cu, Pd, Rh, Ni COMPLEXES
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Cu(OTf)2 and Cu(acac)2 were found to be the most effective catalysts in the reaction of diazo compounds Ph2CN2 (1a), EtOC(O)CHN2 (1b), MeOC(O)CHN2 (1c), MeC(O)CN2C(O)OMe (1d), ClCH2C(O)CHN2 (1e) and CH2N2 (1f) with hydrophosphoryl compounds (MeO)2P(O)H (2a), (t-BuO)2P(O)H (2b), Ph(MeO)P(O)H (2c), (EtO)2P(O)H (2d) and P(O)H (2e) resulting in P-C bond formations.Cu, Pd and Rh acetates and Ni(acac)2 have a much lower efficiency.Chlorines in Cl3CC(O)CH2P(O)(OMe)2 (3k) and Cl2CHC(O)CH2P(O)(OMe)2 (3l) are reduced in the copper catalysed Atherton-Todd reaction.Key words: Catalyst; diazo compound; hydrophosphoryl compound; insertion; phosphonate; phosphinate.
- Polozov, Alexander M.,Mustaphin, Albert H.,Khotinen, Alexander V.
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p. 153 - 160
(2007/10/02)
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- P-H INTERNAL CARBENES. IV. FORMATION OF O,O-DIMETHYL-3-CHLORO-2-OXOPROPYLPHOSPHONATE
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In reactions of ω-polychloro-substituted diazoacetones with dimethyl phosphite catalyzed by copper acetyloacetonate, products of carbenoid P-H introduction are formed. Reduction of the chlorine atoms in them is brought about as a result of a copper-catalyzed Atherton-Todd reaction.
- Polozov, A. M.,Mustafin, A. Kh.
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p. 850 - 852
(2007/10/02)
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- REACTIONS OF POLYHALOGENATED FUNCTIONAL COMPOUNDS WITH METALS AND ELECTROPHILIC REAGENTS XV. REACTIONS OF TRICHLORO- OR TRIBROMOACETYL CHLORIDES WITH ZINC AND ELECTROPHILIC REAGENTS
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The reaction of trichloroacetyl chloride or tribromoacetyl chloride with zinc and acid chlorides in low-polarity aprotic solvents gave 1,2,2-trichloro- or 2,2-dibromo-1-chloro-1-acyloxyethenes. 3-Alkoxy-2,2-dichloropropionyl chlorides were obtained by the reaction of trichloroacetyl chloride with zinc and α-chlorinated ethers.
- Shchepin, V. V.,Novoselova, M. N.,Gladkova, G. E.,Chuprikova, T. Yu.,Efremov, D. I.
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p. 522 - 526
(2007/10/02)
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- General Base Catalysis in the Methanolysis of 4-Nitrophenyl Acetates
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The rates of methanolysis of 4-nitrophenyl acetate, chloroacetate, and dichloroacetate have been measured in the presence of pyridines and imidazoles.Methyl substitution at the 2- and 6-positions in pyridine causes only a slight reduction in reactivity.A
- Neuvonen, Helmi
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p. 669 - 673
(2007/10/02)
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- Kinetics and mechanisms of the acid-catalysed methanolysis of halogen-substituted carboxylic esters
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The methanolysis of chloromethyl dichloroacetate in HClO4/NaClO4 solutions of aqueous methanol at cw 1.30, 2.60 and 5.56 mol/L both at variable and at the constant ionic strengths of 0.5 and 1.0 mol/L and the methanolysis of ethyl trichloroacetate in anhydrous methanol up to 0.1 mol/L hydrogen chloride solutions were studied.The acid-catalysed methanolysis of ethyl trichloroacetate and that of the esters with one or two halogen substituents is proposed to proceed by the normal AAC2 mechanism even in the case when the acid-catalysed hydrolysis in water takes place by the exceptional A-BAC3 mechanism.Under the experimental conditions, the acid catalysed methanolysis of chloromethyl dichloroacetate seems to proceed simultaneously by the AAC2 and A-BAC3 mechanisms.The involvement of the A/BAC3 mechanism in the case of chloromethyl dichloroacetate agrees with the observation that water acts as an effective general base catalyst in the rate-limiting step of the A-BAC3 reactions and that a chloro-substituent in the alkyl component retards the rate of its AAC2 reaction more than in the acyl group, at least in the case of ester hydrolysis.
- Kanerva,Liisa, T.
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p. 329 - 334
(2007/10/02)
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