Elimination Of Hydrogen Chloride Research Articles

Kinetic stability of novel nitrile ylides

A series of relatively stable novel trifluoromethyl substituted nitrile ylides have been generated by base promoted elimination of hydrogen chloride from the corresponding imidoyl chlorides in acetonitrile and aqueous dioxane solution at 25 °C. The formation and decay of these sometimes highly coloured species was monitored spectrophotometrically. The rates of formation were first order in base, and the subsequent reaction with solvent was acid catalysed at high pH's in aqueous systems. Studies in aqueous dioxane indicated that the more stable ylides were also the slowest to form. In acetonitrile as solvent, the ylides underwent addition of solvent at rates which were independent of the base concentration and relatively insensitive to the nature of the substituents. In a number of cases, cycloaddition products were also isolated confirming the 1,3-dipolar nature of these compounds. Protonation of the ylides has also been studied both experimentally in aqueous solution and theoretically. While formation of nitrilium ions by protonation of the ylide carbon atoms is unlikely in aqueous solution since the corresponding amides are not observed as products, these ions have been calculated to be the most favoured protonated forms of ylides either in the gas phase or in a continuum of solvent, irrespective of its polarity. Ab initio calculations were carried out using molecular orbital methods (HF, MP2 and CCSD(T)) with basis sets ranging from 6-31G(d) to 6-311++G(3df,2p) and density functional theory (B3LYP) in conjunction with the polarizable continuum model (PCM) for treating non-specific solvent effects. This discrepancy between experiment and theory suggests a probable involvement of specific solvent interaction in inducing a higher thermodynamic stability of either nitrile carbon or NO2− oxygen protonated forms via hydrogen-bonded complexes.

Halogeno Aldol Reaction of Ethyl Vinyl Ketone and Aldehydes Mediated by Titanium Tetrachloride

A three-component halogeno aldol reaction has been developed by using titanium tetrachloride as the halogen source as well as the Lewis acid mediator. The dehydration and elimination of hydrogen chloride were inhibited by conducting the reaction at 0 °C in dichloromethane or at room temperature with a shortened reaction time. Seven examples were examined, giving good to high yields (61 - 92%) and modest stereoselectivity (syn/anti: 2.2/1.0 - 8.4/1.0).

ChemInform Abstract: Dimerization of Phenylindenes by Means of Perchloroalkanes under Conditions of Phase Transfer Catalysis.

Phenyl substituted indenes 1 react with tetrachloromethane (2a) or hexachloroethane HCE (2b) in the presence of 50% aq. KOH and benzyltriethylammonium chloride (TEBAC) as a catalyst (phase-transfer catalysis, PTC) to give dimers 5 in 23–48% yield. These products are possibly formed via chlorination of carbanions 1 with 2 to give 3, their deprotonation to chlorocarbanions 3, alkylation with chloroindenes 3 to afford 4 and subsequent elimination of hydrogen chloride.

Thermal decomposition of polyamide-6 in the presence of PVC

Besides the monomer some minor but characteristic volatile thermal decomposition products are observed pyrolysing polyamide-6 in the presence of PVC. It was proven that hydrogen chloride thermally eliminated from PVC gives rise to facilitated depolymerization of PA-6, partial hydrolysis of the amide groups, evolution of 6-chlorohexanenitrile, and promoted nitrile and vinyl end group formation. A mechanism is proposed for the advance of these reactions by hydrogen chloride. Depolymerization and hydrolysis are initiated at a considerably lower temperature in the presence of PVC, at the temperature of the hydrogen chloride elimination from the latter. Studying the aspect of high temperature decomposition it was observed that the presence of PVC severely increased the hydrogen cyanide evolution from PA-6 at 900°C.

Reactions in the initial stage of the CVD of BN — a quantum chemical investigation

For a survey over the initial steps in the chemical vapor deposition of boron nitride, we have investigated the mechanism and the energetic course of the gas phase reaction of boron trichloride with ammonia at the level of second-order Moller-Plesset perturbation theory. Furthermore, we have studied dimerization and trimerization of intermediate products. The results affirm previous views that the formation of triaminoborane consists of three sequential substitutions in which a chlorine atom is exchanged for an amino group. While the overall reaction is found to be exothermic, the last substitution reaction is endothermic. In addition we have been able to show that each substitution is a two-step process: an unhindered formation of an ammonia adduct and the subsequent elimination of hydrogen chloride which proceeds through a transition state. Oligomerization and adduct formation are shown to be concurrent processes. We find that the dimerizations are also two-step reactions. At first, a van der Waals complex is formed. The following proper dimerization requires the surmounting of a barrier. From the reaction profile and the relative stabilities of oligomers and adducts we conclude that the polymerization is favored at the stage of BCl(NH2)2.

Azido-1,2,3-triphenylpropenes of Varying Stabilities: A Corrigendum of Structure Assignment

A reinvestigation of the reaction between 2,3-diphenyl-2H-azirine (1) and phenyldiazomethane (2) has shown that a literature report has to be corrected since no vinyl azide 4 but rather the allylic compound 3-azido-1,2,3-triphenyl-1-propene (3) is produced. This stable substance, which can also be prepared by substitution reactions of allylic bromide (E)-10 or from alcohol (E)-11, may be separated into its geometrical isomers (E)-3 and (Z)-3, although these equilibrate through rapid [3,3] sigmatropic migration of the azido group. Attempts to synthesize 4 by dehydration of azido alcohols 7 using methanesulfonyl chloride and sulfur dioxide or by elimination of hydrogen chloride from azides 15 led only to 3 and 2-benzyl-2,3-diphenyl-2H-azirine (14). This heterocycle, which can also be prepared by Neber rearrangement, has been found to be the thermal and photochemical decomposition product of the unstable vinyl azides 4. However, dehydrations of 7 using thionyl chloride at low temperature have led to the first isolation of 1-azido-1,2,3-triphenyl-1-propenes (4). Starting with 3 and various other allylic azides, rearrangement reactions involving sigmatropic shift of the azido group or photochemical cis-trans isomerization have been investigated, as have base-catalyzed (prototropic) rearrangements to give vinyl azides.

Synthesis of ultra-short-acting neuromuscular blocker GW 0430: a remarkably stereo- and regioselective synthesis of mixed tetrahydroisoquinolinium chlorofumarates.

[formula: see text] The stereo- and regioselective synthesis of ultra-short-acting nondepolarizing neuromuscular blocker GW 0430 (5a) is described. Key steps involved the enantioselective transfer hydrogenation of imine 8 employing Noyori's catalyst, the stereoselective crystallization and methanolysis of trans-bataines 11 and 12, and the stereo- and regioselective trans elimination of hydrogen chloride from 14. The latter transformation allowed complete control of the position of the chloro substituent and stereochemistry at the double bond of the linker in 15.

A Convenient and Versatile Route to Hydroquinolines by Inter- and Intramolecular Aza-Diels-Alder Pathways.

Surprisingly, the simplest method possible for o-azaxylylene production, base-induced elimination of hydrogen chloride from amide or sulfonamide derivatives of o-(chloromethyl)aniline, has never been reported. This powerful approach provides easy and stereoselective access to polycyclic hydroquinolines, as shown for an example in Equation (1).

Novel zirconium nitride precursor: synthesis, decomposition pathway, and pyrolysis of [(CH3)3Si]2NH·ZrCl4

C. K. Narula, J. Mater. Chem., 1998, 8, 1881 DOI: 10.1039/A802864H

Synthesis of 1,4-di(n-pyridyl)buta-1,3-diyne and formation of charge-transfer complexes. X-Ray structure of 1,4-di(3-pyridyl)buta-1,3-diyne

Ethynylpyridines have been satisfactorily prepared by two different routes: (a) the Wittig reaction between chloromethylene(triphenyl)phosphine ylide and a pyridinecarbaldehyde, followed by elimination of hydrogen chloride; (b) from the 2-methyl-4-(n-pyridyl)but-3-yn-2-ol intermediate, by elimination of acetone. 1,4-Di(n-pyridyl)buta-1,3-diynes are obtained by oxidative dimerization in good yield. An X-ray structure of the 3-substituted dimer is reported. Mono- and di-methyl salts of the 3-substituted diyne have been obtained and the charge-transfer complexes with tetramethyl-p-phenylenediamine (TMPD) are formed.

Reaction mechanism of poly(vinyl chloride) degradation. Molecular orbital calculations

AbstractSemiempirical Molecular Orbital Calculations (MNDO AM1) support kinetic results concerning the molecular mechanism of thermal degradation of PVC and show that under special conditions radical and ionic mechanisms are also possible. The degradation of poly(vinyl chloride) is a complex chain dehydrochlorination that consists of an initiation process to generate an active intermediate followed by chain reactions that generate additional active intermediates with progressively increased numbers of double bonds. Each intermediate partitions between an intermediate with one more double bond and a stable conjugated polyene with the same number of double bonds. At low and moderate temperatures thermal degradation of PVC in an inert atmosphere is a succession of molecular concerted reactions. The initiation process is a 1,2‐elimination through a four center transition state requiring a synperiplanar conformation. There are two main chain reactions: the first is a 1,4‐elimination from allylic chlorine atoms and methylenes cis to a double bond through a transition state of six centers; the second is a 1,3‐rearrangement of hydrogen atoms catalyzed by hydrogen chloride. The chain reaction is interrupted when a relatively stable trans double bond is formed and no hydrogen chloride is present to catalyze trans‐cis isomerization or 1,3‐rearrangement. Macro carbocations formed by heterolysis of carbon‐halogen bonds in the presence of strong Lewis acids react much faster than does the original PVC in concerted elimination by 1,2‐syn or 1,4‐cis mechanisms, promoting a so‐called catastrophic, very fast degradation. Macro radicals formed by thermal homolysis, irradiation or reaction with promoters can also promote very fast hydrogen chloride elimination because of a special mechanism consisting of a 1,2‐rearrangement of a chlorine atom followed by a concerted 1,3‐elimination through a five center transition state.

Reactions of Benzotriazolo[2,1-a]benzotriazole Derivatives. 1. Synthesis of New Insensitive High-Density Energetic Compounds

Abstract : The sequential preference of electrophilic attack on the dibenzotetraazapentalene ring system 6 has unequivocally been shown to be in the order of position 2(8) > 4(10) >> 1(7) and 3(9). However, nucleophilic substitution reactions with sodium azide were found to be substrate dependent. Substitution occurred at the 3(9)-position of 9 followed by elimination of hydrogen chloride to give 10 while direct substitution of azide for the 4(10)-nitro group of 2 was found to yield 13. The reactivity of the dibenzotetraazapentalene derivatives toward electrophiles and nucleophiles was exploited for the synthesis of the new heterocyclic system 3,4,9,10-bisfuroxano- 5,1 1-dehydro-5H,11H-benzotriazolo(2,1-alpha)benzotriazole 11. From this study the first of a new class of insensitive energetic materials 4 has been synthesized in a straightforward fashion from 2. jg

Enolethers. XXI. Synthesis of 5,5′‐disubstituted 4,4′‐bipyrimidines

Abstract1,6‐Dialkoxy‐3,4‐diones 3 are easily accessible by acylation of enol ethers 1 with oxalyl chloride and subsequent elimination of hydrogen chloride using triethylamine. The open‐chain 2,5‐dimethyl derivative 3b is converted with amidines 4a‐c and S‐methylisothiourea (4d), respectively, to give 2,2′‐disubstituted 5,5′‐dimethyl‐4,4′‐bipyrimidines 5a‐d. The dihydrofuran and dihydropyran derivatives 3c and 3d, however, react with benzamidine (4c) in dimethylformamide only in the presence of calcium hydride as condensation agent yielding 5,5′‐bis(2‐hydroxyethyl)‐ and 5,5′‐bis(3‐hydroxypropyl)‐2,2′‐diphenyl‐4,4′‐bipyrimidine 6a and b.

Degradation and stabilization of poly (vinyl chloride). V. Reaction mechanism of poly(vinyl chloride) degradation

The degradation of poly(vinyl chloride) is a complex chain dehydrochlorination that consists of an initiation process to generate an active intermediate and a series of chain reactions that generates additional active intermediates with progressively increased numbers of double bonds. Each intermediate partitions between an intermediate with one more double bond and a stable conjugated polyene with the same number of double bonds. At low and moderate temperatures the thermal degradation of PVC in an inert atmosphere is a succession of molecular concerted reactions. The initiation process is a 1,2-elimination through a four center transition state requiring a synperiplanar conformation. It can be catalyzed by a molecule of hydrogen chloride that makes possible 1,2-elimination through a transition state of six centers with much lower activation enthalpy but also with very low activation entropy. There are two main chain reactions: the first is a 1,4-elimination from allylic chlorine atoms and methylenes cis- to a double bond through a transition state of six centers; the second is a 1,3-rearrangement of hydrogen atoms catalyzed by hydrogen chloride. The chain reaction is interrupted when a relatively stable trans- double bond is formed and no hydrogen chloride is present to catalyze trans-cis- isomerization or 1,3-rearrangement. Macro carbocations formed by heterolysis of carbon-halogen bonds in the presence of strong Lewis acids react much faster than does the original PVC in concerted elimination by 1,2- syn- or 1,4- cis- mechanisms promoting a so-called ‘catastrophic’, very fast degradation. Macro radicals formed by thermal homolysis, irradiation or reaction with promoters can also promote very fast hydrogen chloride elimination due to a special mechanism consisting of a 1,2-rearrangement of a chlorine atom followed by a concerted 1,3-elimination through a five center transition state.

Transformation and decomposition of 1,1,1-trichloroethane on titanium dioxide in the dark and under photoillumination

Abstract 1,1,1-Trichloroethane (CH3CCl3) in dry air was decomposed to carbon dioxide (CO2), chlorine (Cl2) and hydrogen chloride (HCl) at 313–353 K through a heterogeneous photochemical reaction on titinium dioxide (TiO2). The reaction proceeded on TiO2 mainly through the following two steps: (1) thermal catalytic elimination of HCl to produce 1,1-dichloroethene (CH2CCl2), and (2) photochemical decomposition of CH2CCl2 to CO2 and other products. Photo-oxidation of chloride took place on TiO2, which could keep the catalytic activity of TiO2, since inhibitors like HCl could be removed from the surface. A potential influence of the heterogeneous reaction on estimation of the tropospheric lifetime of CH3CCl3 and/or tropospheric OH budget, is suggested.

Evidence for the three-center elimination of hydrogen chloride from 1-chloroethoxy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for the three-center elimination of hydrogen chloride from 1-chloroethoxyM. Matti Maricq, Jichun Shi, Joseph J. Szente, L. Rimai, and E. W. KaiserCite this: J. Phys. Chem. 1993, 97, 38, 9686–9694Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://doi.org/10.1021/j100140a027RIGHTS & PERMISSIONSArticle Views64Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Tetracyclo[3.2.0.02,7.04,6]hept-1-ene: formation and trapping of 1,2-dehydroquadricyclane. Ab initio calculations on dehydroquadricyclanes

Hydrogen chloride elimination from chloroquadricyclane 14 with tert-butyllithium or n-butyllithium/potassium tert-butoxide in ether at 0 o C led to the title compound 4 as a reactive intermediate. Generating 4 with LDA in the presence of diphenylisobenzofuran (8) or trimethylisoindole (9) afforded the Diels-Alder adducts 18a and 19a. Ab initio calculations at the TCSCF/6-31G * level have been performed on the dehydroquadricyclanes 2-7, and total energies and olefinic strain energies have been determined for those molecules

Reductive elimination of hydrogen chloride from chloro hydrido transition metal complexes: an efficient and simple method for generation of electron-rich, coordinatively unsaturated, reactive intermediates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReductive elimination of hydrogen chloride from chloro hydrido transition metal complexes: an efficient and simple method for generation of electron-rich, coordinatively unsaturated, reactive intermediatesVladimir V. GrushinCite this: Acc. Chem. Res. 1993, 26, 5, 279–286Publication Date (Print):May 1, 1993Publication History Published online1 May 2002Published inissue 1 May 1993https://doi.org/10.1021/ar00029a009RIGHTS & PERMISSIONSArticle Views529Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (967 KB) Get e-Alerts Get e-Alerts

Synthetic approaches to chlorinated 5-hydroxy-5-methyl-2-furanones

The syntheses of chlorinated 5 - hydroxy- furanones with a mono-, di-, and trichloromethyl group at C-5 are described. The 5-chloromethyl hydroxyfuranones were obtained by chlorination of levulinic acid followed by triethylamine promoted elimination of hydrogen chloride. Hydrolyses of chlorinated 4 - cyclopentene- 1,3 -diones yielded 5-dichloromethyl hydroxyfuranones. The trichloromethyl group was incorporated to maleic anhydride through thermal decomposition of sodium trichloroacetate.

Kinetic isotope effects in the reactions of chloroethenes with hydrogen fluoride or deuterium fluoride and the elucidation of reaction pathways

The reaction of tetrachloroethene or trichloroethene with hydrogen fluoride over a chromia catalyst in the vapour phase results in the production of 1,1-dichloro-2,2,2-trifluoroethane (R-123) and 1,1,1,2-tetrafluoroethane (R-134a), respectively. These compounds are formed by the initial addition of hydrogen fluoride to the unsaturate, followed by a series of reactions which involves either the direct, stepwise exchange of chlorine for fluorine or the stepwise elimination of hydrogen chloride and addition of hydrogen fluoride to the reaction precursors. The substitution of deuterium fluoride for hydrogen fluoride in the reaction with tetrachloroethene causes the reaction rate to be significantly enhanced, the selectivities to the product precursors to be decreased, and the selectivities to over-fluorinated products to be increased. These results are consistent with a reaction pathway involving predominantly chlorine/fluorine exchange. Reaction of deuterium fluoride with trichloroethene causes no change in the product selectivities, relative to the reaction with hydrogen fluoride. However, analysis of the isotope distribution of the products in this system reveals that both chlorine/fluorine exchange and HF addition/HCl elimination pathways are in evidence.