Elimination Of Hydrogen Chloride Research Articles

Neue Synthesewege zu chlorsubstituierten Tropon-Derivaten

New Syntheses of Chloro-Substituted Derivatives of Tropone The Diels-Alder reaction of donor-substituted 1.3-dienes with tetra chlorocyclopropene leads to novel bicyclo[4.l.0]heptenes, which on acidic hydrolysis and oxidalion yield a new series of chloro-substituted derivatives of tropone by way of elimination of hydrogen chloride concerted with an electrocyclic opening of the three membered ring.

Mechanisms of pyrolysis of fluoropolymers

A systematic study of the mechanisms of the pyrolysis of fluoropolymers was made by means of pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and direct Py-MS. For perfluoropolymers and chlorine-containing fluoropolymers the depolymerization reaction predominates during pyrolysis. However, the introduction of OCF 3 groups into perfluoropolymers in place of F atoms brings about significant changes in their mode of degradation. The OCF 3 groups activate the F atoms attached to the same carbon atoms and make them easier to transfer. Therefore, random chain cleavage accompanied by the F transfer becomes predominant in the course of the pyrolysis. When the F atoms of perfluoropolymers are partly replaced by H atoms, elimination of hydrogen fluoride and chain cleavage accompanied by H transfer would occur with great ease. For fluoropolymers containing H, Cl and OCF 3 as side groups, the depolymerization, the elimination of hydrogen chloride and hydrogen fluoride and the random chain cleavage accompanied by H and F transfer would occur simultaneously and compete with each other.

Acyclic nucleoside analogues: methods for the preparation of 2′,3′-secoguanosine, 5′-deoxy-2′,3′-secoguanosine, and(R,S)-9-[1-(2-hydroxyethoxy)-2-hydroxyethyl]guanine

A high yielding, one-pot method for the preparation of 2′,3′-secoguanosines 5 and 6 by treatment of 5′-deoxyguanosine (4) and guanosine (2), respectively, with sodium periodate and then sodium borohydride is described. The final products 5 and 6 were purified from contaminating salts by passage of the reaction mixture over a column of activated charcoal. An additional acyclic derivative 14 was prepared in racemic form by an approach involving a novel condensation reaction. Alkylation of N2,9-diacetylguanine (8) with 2,3-dichlorotetrahydrofuran (7) resulted in selective N-9 alkylation to give adduct 9a. Compound 9a was deacylated with ammonium hydroxide to give 10, which was monomethoxytritylated to 11. Elimination of hydrogen chloride from 11 using potassium tert-butoxide afforded 12, which was reacted with OsO4–NaIO4 followed by treatment with NaBH4 to give 13, which was then deprotected with acid to 14. Compounds 5, 6, 14, and 16 were tested in vitro against herpes simplex virus types 1 and 2 and were found to be inactive.

Thermal dehydrochlorination of poly(vinyl chloride), 2. Transiently and permanently acting structural defects

AbstractSamples with an increased content of chloroallyl structures were prepared by chemical degradation of poly(vinyl chloride) (PVC) using potassium tert‐butoxide. The samples were thermally dehydrochlorinated in an inert atmosphere, and their dehydrochlorination curves were determined by the continuous potentiometric method. The results show that the chloroallyl structures affect the dehydrochlorination of PVC only transiently. The same conclusion is obtained by an analysis of experimental data of the dehydrochlorination of PVC samples enriched in structures with the chlorine atom bound to the branching site (structures with the chlorine atom at the tertiary carbon atom). A general conclusion is that all structural defects, which facilitate the elimination of hydrogen chloride along the polymer chain and exist in the polymer before its heat stress, play only a transient role in the thermal dehydrochlorination of PVC. These structural defects initiate the splitting‐off of hydrogen chloride during the induction period of dehydrochlorination and form conditions for a gradually increasing effect of the basic initiation mechanism, which in the course of dehydrochlorination gives rise to chloroallyl structures. The formation of chloroallyl structures is brought about by a reaction between regular structural PVC units and s‐cis‐enone, dienone, or polyenone structures. A possible mechanism of this reaction, consisting in an interchain syn‐elimination of hydrogen chloride, is suggested.

1-Chloro-1,3-butadiene Copolymers VI. Structure of the Diene Unit and Monomer Sequence Distribution in the Copolymer with Styrene

Microstructures in the copolymer of 1-chloro-1,3-butadiene (CB) and styrene (St) obtained by radical polymerization in bulk were investigated by spectroscopic methods. The microstructure of CB units in the copolymer was found as follows: 60% 1,4 and 40% 3,4 structures by 1H NMR; ca. 50% trans-1,4, ca. 5% cis-1,4, and ca. 45% 3,4 structures by IR. About 60% chlorine in the 1,4 CB unit was estimated to be very reactive because it is an allylic chlorine. After hydrogen chloride elimination from poly(CB-co-St), diad(1,4 CB-1,4 CB) and triad(1,4 CB-1,4 CB-1,4 CB) were determined by UV-visible spectroscopy. The results were in accord with the theoretical ones calculated from the monomer reactivity ratios derived from the terminal model (simple Markov) and the feed composition; the distribution of 1,4 and 3,4 structures was assumed completely random (Bernoullian).

Cycloadditions in syntheses. XXVI 1,2-Dihydrocyclobuta(b)naphthalene-3,8-diones : Synthesis by photochemical means and their reactions via 2,3-dimethylene-1,4-dioxo-1,2,3,4-tetrahydronaphthalenes.

2-Chloro-1, 4-naphthoquinone undergoes photochemical 2+2 addition to alkenes. Elimination of hydrogen chloride from the adducts provides a facile and general synthetic method for 1, 2-dihydrocyclobuta[b]naphthalene-3, 8-diones. Heating of the latter compounds affords 2, 3-dimethylene-1, 2, 3, 4-tetrahydronaphthalene-1, 4-diones, which react in situ with alkenes to give the 4+2 adducts. 1-Formyl-1, 2-dihydrocyclobuta[b]naphthalene-3, 8-dione obtained by the use of the above two-step procedure using acrolein dimethylacetal as the alkene in the first step affords upon heating 1H-naphtho[2, 3-c]pyran-2, 10-dione via electrocyclization of the corresponding dimethylenecompound. If an enone is used as the alkene in the first step, the addition occurs in a 4+2 manner to give directly 4H-naphtho[2, 3-b]pyra-5, 10-diones.

Laser Induced Chemical Reactions in Combustion and Industrial Processes

The rapid development of powerful UV‐laser sources allows the investigation of macroscopic and microscopic details of elementary chemical reactions important in combustion processes. Experimental results on the effect of selective translational and vibrational excitation of reactants in elementary combustion reactions using laser photolysis and time‐resolved atomic line resonance absorption, laser‐induced fluorescence and CARS spectroscopy are compared with the results of theoretical studies on ab initio potential energy surfaces and thermal rate parameters. Thermal elimination of hydrogen chloride from 1,2‐dichloroethane and 1,1,1‐chlorodifluoroethane is a main industrial route to some important monomer compounds. Inducing these radical chain reactions by UV‐exciplex laser radiation offers the advantage that a monomolecular process with low activation energy becomes the rate determining step. This allows lower process temperatures with decreasing energy expense and avoiding the high temperature formation of byproducts.

Catalytic dehydrochlorination of 1,1,2-trichloroethane over CsCl supported on silica gels

The catalytic dehydrochlorination of 1,1,2-trichloroethane (TCE) into vinylidene dichloride (VDC) over CsCl supported on silica gels was studied using pulse and flow reactors to find a selective process to recover the hydrogen chloride produced. The supporting silica gel and the level of CsCl impregnation were most influential for the catalytic activity. The conversion was as high as 90% at 90% selectivity in the first pulse over CsCl/MB-3A at 250°C. However, a significant decrease in activity was observed with repeated pulses or using a flow reactor (0.01 atm, TCE), suggesting that the desorption of hydrogen chloride is limited, since the activity could be thermally regenerated. Bifunctional cooperation of hydroxyl groups on the silica surface is assumed to accelerate the elimination of hydrogen chloride.

Grafted polypropylene containing chlorohydrin groups—II: Analysis of polymer and its reactivity

I.R. analysis of isotactic powdered polypropylene containing acrylic acid grafts, with acidic groups esterified with epichlorohydrin, has revealed that the carbonyl contents gradually increase when the esterification is carried out at 90 to 120° while the concentration of hydroxyl groups changes proportionally to the content of chlorohydrin groups in the polymer. At esterification temperatures exceeding 90°, the product loses chlorine by hydrogen chloride elimination. The observed data are in accordance with the mechanism of dehydrochlorination of chlorohydrin groups without intermediate formation of the epoxide ring. From the polymer containing chlorohydrin groups, no chlorine is evolved even at temperatures as high as 120°. During thermal treatment with a basic reagent, the generated epoxy-ring remains only partially. When there are also primary or secondary amines in the system, the transformation to the epoxide is enhanced, the amine being eventually bonded to polymer.

Reaction of bis(salicylaldehyde hydrazone) vanadium(IV) dichloride with aromatic and heterocyclic amines

Bis(salicylaldehyde hydrazone)vanadium(IV) dichloride undergoes reaction with aromatic amines such as aniline, 1,4-diaminobenzene, heterocyclic amines such as aminopyridine and nucleotides such as adenine. Elemental analysis, magnetic susceptibility measurements, electronic, infrared and esr spectral data indicate that the compound formed in the case of reaction with aniline is bis(salicylaldehyde hydrazone) bis(anilinato)vanadium(IV) with elimination of hydrogen chloride. Similar compounds are formed as a result of reaction with the other amines. In addition, the elimination reaction has been studied using the hydrazone derived from phenylhydrazone which gives similar products on reaction with the aromatic and heterocyclic amines.

The chloroindolenine – imino ether – oxindole sequence. A reexamination

The chloroindolenines of deserpidine and reserpine, and the isomeric chloroindolenines derived from yohimbine – characterized for the first time – have been treated with methanol and methoxide ion under a variety of conditions. In the traditional medium of methanolic hydroxide, chlorodeserpidine partially undergoes rearrangement to imino ether, whereas chlororeserpine suffers only substitution of chloride by methoxide; only the α-isomer of the two yohimbine chlorides undergoes rearrangement to a methyl imino ether, the β-isomer being degraded to an intractable mixture. In refluxing neat methanol, the α-chloride of yohimbine rearranges readily and cleanly to imino ether at a rate comparable to that of chlorodeserpidine rearrangement, but vastly greater than that of the β-chloride. However, under silver oxide catalysis all the chloroindolenines rearrange at closely similar rates. The rearrangement of chloroindolenine to methyl imino ether is stereospecific, α-chloride leading to α-spiro imino ether and β-chloride to β-spiro imino ether. The results are rationalized on the basis of stereoelectronic considerations applied to a process of addition of methanol to the imine bond, followed by elimination of hydrogen chloride from the methanol adduct.

ATTEMPTED SYNTHESIS OF TRIMESITYLPHOSPHAETHENE; OBSERVATIONS RELATED TO THE MECHANISM OF ACID CATALYZED NUCLEOPHILIC SUBSTITUTIONS AT PHOSPHORUS (III)

Abstract Trimesitylphosphaethene (MesP[dbnd]CMes2, If) is of interest as a sterically protected and presumably very stable phosphaalkene. Its synthesis was attempted along three different routes. The first two routes were modelled after the well-documented syntheses by phosphaalkenes by base catalyzed elimination of hydrogen chloride from MesPCICHMes2 (3). In the first approach, 3 could not be obtained from the precursor MesP(NEt2)CHMes2 (4) by treatment with hydrogen chloride. Instead, the phosphonium salt [MesPH(NEt2)CHMes2]⊕Cl⊖ (2) was formed; (2) is of interest as a “frozen” intermediate in the acid catalyzed nucleophilic substitution at phosphorus(III). The mechanistic implications of its formation and the reasons for its lack of reactivity are discussed. In the second approach, 3 was obtained from the reaction of MesPCl2 (8) with α-potassiodimesityl-methane. However, several attempts to eliminate hydrogen chloride from 3 were unsuccessful. Similarly, the third route, aimed at the preparation of CIP[...

THE REACTION OF 2H-THIIN DERIVATIVES WITH PERACID. RING CONTRACTION AND ALKOXYLATION REACTIONS

Abstract The cycloaddition reaction of aromatic thioketones (aryl naphthyl thioketones and 2-benzofuryl phenyl thioketone) with 2-chloroacrylonitrile followed by elimination of hydrogen chloride gave some 2H-thiin derivatives. The products reacted with MCPBA and an alcohol to afford ring-contracted product and alkoxylated derivatives.

The use of organotin compounds in the thermal stabilization of poly(vinyl chloride). VI. An assessment of the relative importance of HCl‐scavenging, exchange, and addition reactions

AbstractReactions of PVC with three representative stabilizers Bu2SnY2 (Y = OCOC11H23, SCH2COOCH2CH(Et)CH2CH2CH2CH3, OCOCH=CHCOOMe) in solution and under nitrogen were studied by two principal methods. First, using stabilizers with radioactive labels in the Y groups, the uptake of these groups by virgin and degraded polymer was measured. The UV‐visible absorption spectra of the stabilized polymers are discussed. Second, the effect of these three stabilizers on the rate of elimination of hydrogen chloride from heated PVC was studied. It is shown that the effects of HCI‐scavenging and of exchange reactions in suppressing the evolution of HCI can be separately evaluated. The thermal decomposition of dibutyltin bis(methyl maleate) to give maleic anhydride is reported. Interpretation of the observations is made in terms of assessing the relative importance of the various polymer–stabilizer reactions in promoting stabilization.

ChemInform Abstract: CYCLOADDITION REACTIONS OF HETEROAROMATIC THIOKETONES WITH MALEIC ANHYDRIDE, NORBORNENE, ACRYLONITRILE, STYRENE, AND 2‐CHLOROACRYLONITRILE

AbstractDie Thioketone (III) bzw. (XII) reagieren mit den Verbindungen (II), (IV), (VI) und (X) unter Ringschluß zu den angegebenen farblosen bis purpurroten Diels‐Alder‐Addukten.

Carbon as a catalyst in oxidation reactions and hydrogen halide elimination reactions

Carbon catalyses many reactions, mainly oxidation reactions with oxygen and with halogens, e.g. SO 2 + 1 20 2 → SO 3 , or CO + Cl 2→ COCl 2. It is known, however, that different carbons behave quite differently in the reduction of oxygen on fuel cell cathodes. Therefore the catalytic activity of carbons has been studied in other reactions. A convenient test reaction is the oxidation of dilute aqueous sulphurous acid. It became apparent that all catalytically active carbons contain small quantities of nitrogen, and inactive carbons such as wood charcoal or carbon blacks can be rendered highly active by treatment with N H 3 or HCN at elevated temperatures. Photoelectron spectra indicate that the catalytic activity increases parallel to the incorporation of a nitrogen species which is pyridine-like, i.e. incorporated in the aromatic layers. Treatment with NH 3 at 900 °C leads also to massive gasification of the carbons, increasing their surface area. Other reactions studied included the oxidation of aqueous oxalic acid and of methanol to formaldehyde. A quite different type of reaction is the elimination of hydrogen chloride from 1-chloroalkanes, e.g. 1 -chlorobutane. Again, activity changes in parallel to nitrogen content. Reaction products are olefins, dimers of the alkyl groups, and a polymer on the catalyst surface. The formation of alkyl dimers, e.g. n-octane in the case of n-butylchloride, suggests that radicals are involved in the reaction.

PHOTOCHEMICAL 2+2 CYCLOADDITION OF 2-CHLORO-1,4-NAPHTHOQUINONE TO ALKENES. A NOVEL SYNTHESIS OF 1,2-DIHYDROCYCLOBUTA[b]NAPHTHALENE-3,8-DIONES

Abstract 2-Chloro-1,4-naphthoquinone undergoes photochemical 2+2 addition at its 2- and 3-positions to alkenes. An elimination of hydrogen chloride from the adducts provides a facile and general synthetic method of 1,2-dihydrocyclobuta[b]naphthalene-3,8-diones.

Cycloaddition Reactions of Heteroaromatic Thioketones with Maleic Anhydride, Norbornene, Acrylonitrile, Styrene, and 2-Chloroacrylonitrile

Abstract Heteroaromatic thioketones react with maleic anhydride, norbornene, acrylonitrile, and styrene to form the Diels-Alder adducts, respectively. The thioketones also undergo cycloaddition with 2-chloroacrylonitrile followed by elimination of hydrogen chloride to give heteroaromatic analogues of o-quinodimethan derivatives. In these reactions, the thioketones act as a heterodiene on the dienophiles to give [4+2]cycloadducts regioselectively.

Infrared laser multiple-photon dissociation of CDCl3 in a molecular beam

Pulsed CO2 laser multiple-photon dissociation of CDCl3 was examined in a molecular beam using 11 μ radiation. The only observed dissociation channel was hydrogen chloride elimination (≳99.1%), with no evidence of simple chlorine atom cleavage (<0.9%). Implications for isotope separation are discussed.

A Route from 1,1,1,3-Tetrachloro-3-phenylpropane to Ethynyl Phenyl Ketone Involving Elimination of Hydrogen Chloride and 1,3-Proton Transfer

Abstract The treatment of 1,1,1,3-tetrachloro-3-phenylpropane with alkali in ethanol affords ethynyl phenyl ketone and its acetal in good yields. This reaction proceeds through the elimination of hydrogen chloride and an efficient 1,3-proton transfer catalyzed by base. Ethyl cinnamate is obtained in only 2% yield.