Replacement Of Halogen Atom Research Articles

Theoretical study on the substituent effect of halogen atom at different position of 7-azaindole-water derivatives: relative stability and excited-state proton-transfer mechanism

We have theoretically investigated the substituted effect on the first excited-state proton-transfer process of nX7AI-H2O (n = 2~6, X = F, Cl, Br) complex at the TD-M06-2X/6-31 + G(d, p) level. Here X is the substituted halogen atom, and n value denotes the substituted position of X, such as C2, C3, C4, C5, or C6. For the substituted 7-azaindole clusters, 6X7AI-H2O molecule is the most stable structure in water. The replacement of halogen atom X does not affect the characters of the HOMO and LUMO, but influence the S0 → S1 adiabatic transition energies of nX7AI-H2O (n = 2~6, X = F, Cl, Br). Our calculated results show that the double proton transfer occurs in a concerted but asynchronous protolysis pathway no matter which H atom is replaced by halogen atom. The halogen substitution changes the structural parameters evidently and leads to amply the asynchronousity during the proton-transfer process. The ESPT barrier height increases or decreases due to the halogen atom and substituted position.

Chemoselective Hydrodehalogenation of Organic Halides Utilizing Two-Dimensional Anionic Electrons of Inorganic Electride [Ca2N]+·e.

Halogenated organic compounds are important anthropogenic chemicals widely used in chemical industry, biology, and pharmacology; however, the persistence and inertness of organic halides cause human health problems and considerable environmental pollution. Thus, the elimination or replacement of halogen atoms with organic halides has been considered a central task in synthetic chemistry. In dehalogenation reactions, the consecutive single-electron transfer from reducing agents generates the radical and corresponding carbanion and thus removes the halogen atom as the leaving group. Herein, we report a new strategy for an efficient chemoselective hydrodehalogenation through the formation of stable carbanion intermediates, which are simply achieved by using highly mobile two-dimensional electrons of inorganic electride [Ca2N]+·e- with effective electron transfer ability. The consecutive single-electron transfer from inorganic electride [Ca2N]+·e- stabilized free carbanions, which is a key step in achieving the selective reaction. Furthermore, a determinant more important than leaving group ability is the stability control of free carbanions according to the s character determined by the backbone structure. We anticipate that this approach may provide new insight into selective chemical formation, including hydrodehalogenation.

What affects the rate of free radical polymerization of a multifunctional acrylate photoinitiated by cyanine borate salts? Part I. Kinetic studies

Cyanine dyes, widely used in color photography, can also be used as initiators of radical polymerization, initiated with visible light. The aim of this work was to check the possibility of application of borate salts of these dyes as photoinitiators of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate - TMPTA and to determine the effect of photoinitiator structure on the polymerization rate. 32 symmetric cyanine dyes - derivatives of benzothiazole and benzoxazole have been synthesized Their structures were differentiated by changing of heteroatom (S or O), substituent in the phenyl ring as well as the type of substituents in polymethine chain. Spectroscopic investigations of dyes used as well as their borate salts showed the intensive absorption band localized for thiocarbocyanine dyes in the range 550-600 nm while for carbocyanine dyes - in the range 480-510 nm. Replacement of halogen atom or ethylsulfate anion in the cyanine dye molecule to the following anions: n-, sec- or tert-butyltriphenylborate and tetra-n-butylborate gave the borate salts of cyanine dyes. 150 various borate salts of cyanine dyes have been used as photoinitiators of TMPTA photopolymerization. It has been stated that the ability of initiation of TMPTA [as 10 vol. % solution in 1-methyl-2-pyrrolidinone (MP)] polymerization depends on the type of heteroatom in the dye molecule, the type of substituent in the phenyl ring, the type of substituent in mezo position in polymethine chain and on borate anion structure. It has been also found that monomer conversion and quantum yield of the process depend also on the chemical structure of photoinitiator..

Reactions of nucleophilic substitution involving solid organic halogen compounds under shear deformation at high pressure

Under conditions of shear deformation and high pressures (SD+HP), reactions of nucleophilic substitution were studied: 1) the replacement of aliphatic halogen atom with alkaline metal halides (halo-substituted aliphatic carboxylic acids, 1-bromoadamantane); 2) the replacement of halogen atom in aromatic nucleus (halobenzoic acids, dihalobenzenes) with halogen of salt; 3) the replacement of aliphatic halogen with hydroxyl (hydrolysis in a solid phase); 4) the replacement of halogen with amino group under deformation of the samples of ammonium α-halocarboxylates to give the corresponding amino acids. It was found that the exchange of the halogen atoms bonded with aliphatic carbon is most intensive in the mixtures of alkaline metal iodides with bromo-substituted acetic and propionic acids: the exchange reaction in these mixtures is observed even during grinding in the mortar. Unlike the liquid phase, under conditions of SD+HP exchange of the halogen atom of the aromatic nucleus with alkaline metal halides, proceeds successfully, and the reactivity of halides increases in the series Na < K < Rb < Cs. Under SD+HP, 1-Br-adamantane reacts with water to form 1-adamantanol. A high reactivity of the water adsorbed by the reagents is observed.

Poly(monophosphazophosphazenes): New Polymers with N:PR3 Side Groups

Phosphazene high polymers with N=PR 3 (phosphazo) side groups were prepared with trifluoroethoxy, phenoxy, anilino, and propylamino side groups. Small-molecule cyclic counterparts were also synthesized as model systems for the macromolecular inactions. These compounds were prepared using both (trichlorophosphazo)pentachlorocyclotriphosphazene (N 3 P 3 Cl 5 NPCl 3 ) and (trichlorophosphazo)pentafluorocyclotriphosphazene (N 3 P 3 F 5 NPCl 3 ) as the starting materials. Specifically, the synthesis of monophosphazophosphazene polymers through the thermal ring-opening polymerization of N 3 P 3 Cl 5 NPCl 3 at 150-180°C or of N 3 P 3 F 5 NPCl 3 at 200-210°C is reported. Differences in the reactivity of the phosphazochloro- and the phosphazofluorophosphazenes to halogen replacement reactions were found at both the cyclic trimeric and high polymeric levels. In general, replacement of the chlorine atoms by organic groups was achieved with greater ease than the replacement of fluorine atoms. For the reagents studied, the replacement of halogen atoms by sodium trifluoroethoxide was more facile than with the other nucleophiles. A comparison is made between the properties of monophosphazophosphazenes, classical phosphazenes, and 1,1-diphosphazophosphazenes

Nucleophilic replacement of halogen atom by amino group in 1-halomethyl-o-carboranes

Nucleophilic replacement of halogen atom by amino group in 1-halomethyl-o-carboranes

Cryoscopic investigation of the complex formation of organotin compounds

1. A method of cryoscopic determination of the equilibrium constants of the stepwise reactions of complex formation in solution was proposed. 2. The interaction of RSnX3, R2SnX2, R3SnX (R=C2H5, C4H9, X=Cl, Br, -OOCCH3) with oxygen- and nitrogen-containing compounds in benzene was investigated. The equilibrium constants of the reactions of complex formation were determined (25 systems). 3. The processes of complex formation of organotin compounds with monodentate ligands proceed in stages with the formation of penta- and hexacoordinated compounds. Bidentate ligands, as a rule, give 1∶1 complexes in one step. 4. Replacement of halogen atoms by alkyl and acyl groups reduces the coordination capacity of organotin compounds. The steric factor has an appreciable influence on the course of the reaction of complex formation. 5. The formation of complexes of dibutyltin diacetate with donor molecules capable of giving hydrogen bonds [CH3OH, (C4H9)2NH] proceeds differently from that with the usual ligands. A hypothesis is advanced on the presence of a supplementary interaction in these systems on account of hydrogen bonds with the carbonyl oxygen of acyl groups. 6. A method of cryoscopic titration was proposed for the analysis of mixtures of organotin halides of various degrees of alkylation.

Analysis of the valence electronic structures of some tin(IV) compounds

An analysis of the charge distributions in a number of SnIV compounds, calculated by a modified CNDO method, is presented. The series includes tin halides and their anions, and a series of halogen-substituted methylstannanes. Overall, the results accord well with chemical intuition and, with few exceptions, fit into a pattern with clear-cut trends. Stannane and the methylstannanes are highly ‘covalent’ compounds, whilst the tetrahalides are much more ‘ionic’. Gradations occur along both series. Replacement of halogen atoms by methyl groups reduces the polarity of the tin–halogen bond because methyl groups act in this context as sources of electrons, largely via the π type orbitals. The involvement of 5d orbitals is small in stannane and the methylstannanes, larger in the tetrahalides and largest in the hexahalide anions. This involvement is also more marked with increasing atomic weight of the bonded halogen.

Homolytic halogen replacement in halogenobenzenes by radiolytically formed aqueous hydrogen (tritium) atoms

Replacement of halogen atoms by aqueous tritium atoms occurs in competition with hydrogen replacement, the relative importance of the two processes depending on the nature of the halogen and the concentration of added copper(II) ion.