Showing papers in "Phosphorus Sulfur and Silicon and The Related Elements in 1983"
TL;DR: In this paper, 2-Mercapto-2-thiono-1,3,2-dioxaphospholanes and dioxaphophosphorinanes, have been synthesized by the reactions of phosphorus pentasulphide with some 1, 2-diols.
Abstract: 2-Mercapto-2-thiono-1,3,2-dioxaphospholanes and dioxaphosphorinanes, have been synthesized by the reactions of phosphorus pentasulphide with some 1,2-diols (viz., butane-2,3-diol and 2,3-dimethylbutane-2,3-diol) and 1,3-diols (viz., 2-methylpentane-2,4-diol, 2,2-dimethylpropane-1,3-diol and 2,2-diethylpropane-1,3-diol) in 1:2 molar ratio in dry benzene. These volatile compounds have been purified by distillation under reduced pressure. The 2-methylpentane-2,4-diol derivative, however, decomposed during attempted distillations. These new compounds have been characterized by elemental analysis, molecular weight determinations, measurement of pK a values and IR as well as NMR spectroscopic studies. The ammonium and sodium salts of some of these acids have also been characterized.
84 citations
TL;DR: In this article, the authors summarized their work on acylphosphines and alkylidene-alkylide-phosphine compounds under ordinary conditions and showed that these compounds exist only thirty years ago.
Abstract: The following article summarizes our work on acylphosphines and acylphosphides as well as on alkylidene- and alkylidynephosphines, most of which were thought only thirty years ago not to exist under ordinary conditions.
74 citations
TL;DR: In this paper, Horiguchi and Kandatsu29 announced the isolation of a compound having the carbon-to-phosphorus bond, viz. 2-aminoethylphosphonic acid, from ciliated protozoa.
Abstract: Up to 1959, all the organic phosphorus compounds isolated from living things had been shown to have the carbon-containing portion of the molecule attached to either oxygen or, less commonly, to nitrogen on the phosphorus atom. It came therefore as a distinct surprise when Horiguchi and Kandatsu29 announced the isolation of a compound having the carbon-to-phosphorus bond, viz. 2-aminoethylphosphonic acid, from ciliated protozoa. Since then several other phosphorus-carbon containing compounds have been detected in nature and isolated. Most of them contain nitrogen also, e.g.
60 citations
TL;DR: In this paper, the authors generalize the results obtained so far, allowing a critical assessment of the conditions and restrictions for the realization of the cyclization of allenic system of π-bonds and phosphorylic group.
Abstract: In the past several years the reaction ability of phosphorylated allenes with electrophilic reagents has been intensively studied. The experimental data showed that during the interaction of reactants a cyclization of allenic system of π-bonds and phosphorylic group (O[dbnd]P[sbnd]C[dbnd]C[dbnd]C) takes place leading to the formation of P,O-containing heterocyclic compounds. The present paper generalizes the results obtained so far, allowing a critical assessment of the conditions and restrictions for the realization of this interesting reaction.
44 citations
TL;DR: The synthesis, chemical and spectral properties of phosphinothricin analogues which either have other groups than methyl attached to phosphorus (30 to 35) or bear substituents on nitrogen (43 to 50) are described and the activity of some of these derivatives as glutamine synthetase inhibitors and contact herbicides is reported as mentioned in this paper.
Abstract: The synthesis, chemical and spectral properties of phosphinothricin analogues which either have other groups than methyl attached to phosphorus (30 to 35) or bear substituents on nitrogen (43 to 50) are described and the activity of some of these derivatives as glutamine synthetase inhibitors and contact herbicides is reported.
43 citations
TL;DR: In this article, the synthesis of the 12H-dibenzo[d,g][1,3,2]dioxaphosphocin ring system from 2,2′-alkylidene bisphenols and phosphorus trichloride is described.
Abstract: The synthesis of the 12H-dibenzo[d,g][1,3,2]dioxaphosphocin ring system from 2,2′-alkylidene bisphenols and phosphorus trichloride is described. The 1H NMR shows evidence for long range through-space coupling of the C-12 methine proton to phosphorus.
37 citations
TL;DR: Pyridin-2,6-dicarbothiosaure bildet with Pyridin ein 1:1-Addukt, dem die Struktur eines Pyridisinium-pyrideinium pyrinium 2,6biscarbothioats zukommt, wie aus Rontgen- und and other spektroskopischen Daten abgeleitet werden kann as mentioned in this paper.
Abstract: Pyridin-2,6-dicarbothiosaure bildet mit Pyridin ein 1:1-Addukt, dem die Struktur eines Pyridinium-pyridinium-2,6-biscarbothioats zukommt, wie aus Rontgen- und anderen spektroskopischen Daten abgeleitet werden kann. Zusatzlich werden einige verwandte Verbindungen beschrieben. Pyridine-2,6-dicarbothioic acid and pyridine from an 1:1 adduct which according to X-ray and other spectroscopic data is actually pyridinium pyridinium-2,6-biscarbothioate. In addition, serveral related compounds are described.
25 citations
TL;DR: In this article, the Wittig-Horner reaction has been explored with phosphonates, CO[sbnd]R2, CN) with K2CO3 or KHCO3 as bases in water or anhydrous solvents such as THF, toluene and CH2Cl2, with or without phase-transfer catalysis.
Abstract: The Wittig-Horner reaction has been explored with phosphonates , CO[sbnd]R2, CN) with K2CO3 or KHCO3 as bases in water or anhydrous solvents such as THF, toluene and CH2Cl2, with or without phase-transfer catalysis. The scope and limitations of these procedures, which can give excellent yields (75–100%), have been compared. Olefins are formed with E geometry for A = COOEt, CO[sbnd]R2 (R′ [dbnd] H) and as mixtures of E/Z compounds for A [dbnd] CN. Side reactions (i.e. crotonization, isomerization, saponification, Knoevenagel and Cannizzaro reactions) can be eliminated using reaction conditions modified for each case. Optimum times and temperatures of the reactions have been determined for improved yields. The use of a two phase liquid-liquid system in water without solvent often gives excellent yields (A [dbnd] COOEt, COR2, CN). However, benzaldehyde gives almost quantitative yields (A [dbnd] COOEt) in a solid-liquid heterogenous medium in boiling toluene using solid K2CO3 or KHCO3, with or withou...
24 citations
TL;DR: In this article, the photoelectron and electron spin resonance spectroscopic assignments are supported by MNDO as well as parametrized HMO calculations, and they are shown to be consistent with the results reported in this paper.
Abstract: Trimethylsilyl-and cyano-substituted thiophenes can be reduced in THF using potassium and the resulting radical anions can be characterized by their electron spin resonance spectra. Attempts to oxidize thiophene derivatives with low first ionization potentials to their radical cations using the AlCl3/H2CCl2 oxidizing system failed except for dithienyldisulfide, the radical cation of which rearranges under the reaction conditions to the one of dithieno[2,3-b,2′,3′-e]-p-dithiin. The photoelectron and electron spin resonance spectroscopic assignments are supported by MNDO as well as parametrized HMO calculations. Trimethylsilyl-und Cyan-substituierte Thiophene lassen sich in THF mit Kalium reduzieren und die entstehenden Radikalanionen durch ihre Elektronenspinresonanz-Spektren charakterisieren. Versuche, Thiophen-Derivate mit niedriger erster Ionisierungsenergie duch Umsetzung mit AlCl3/H2CCl2 zu ihren Radikalkationen zu oxidieren, blieben dagegen erfolglos. Eine Ausnahme ist Dithienyldisulfid, des...
24 citations
TL;DR: In this article, the synthesis of the dibenzo[d,f][1,3,2]dioxaphosphepin ring system from substituted biphenyl-2,2′-diols and alkylphosphonous dichlorides is described.
Abstract: The synthesis of the dibenzo[d,f][1,3,2]dioxaphosphepin ring system from substituted biphenyl-2,2′-diols and alkylphosphonous dichlorides is described. The NMR spectral data are consistent with either rapidly interconverting ring conformers or a static non-planar ring conformation.
24 citations
TL;DR: In this paper, N, N-dialkylarylamines and N,N-dialklarylamine are lithiated with n-butyllithium (n-BuLi) under the assistance of tetramethylethylenediamine (TMEDA) in the ortho-position.
Abstract: N,N-dialkylarylamines and N,N-dialkylbenzylamines are lithiated with n-butyllithium (n-BuLi) under the assistance of tetramethylethylenediamine (TMEDA) in the ortho-position. According the Eqs. (1) and (4) triarylphosphines (30–50%) are obtained. 1-(N,N-dimethylamino)-naphthalene and N,N-dimethyl-1-(1-naphthyl)-ethylamine 18 are lithiated in the 8-position. In N,N-dimethyl-1-(2-naphthyl)-ethylamine 19 the 1- and 3-position is lithiated in nearly equal amount. Experiments to introduce lithium twice into the model compounds 28–30 are without success. N,N-Dialkylarylamine und substituierte N,N-Dialkylbenzylamine werden mit n-Butyl-lithium (n-BuLi) unter Mitwirkung von Tetramethylethylendiamin (TMEDA) in ortho-Stellung lithiiert und durch Umsetzung nach (1) bzw. (4) in Triarylphosphine (30–50%) uberfuhrt. 1-N,N-Dimethylamino)-naphthalin und N,N-Dimethyl-1(1-naphthyl-ethylamin 18 werden in 8-Stel-lung lithiiert. In N,N-Dimethyl-1-(2-naphthyl)-ethylamin 19 tritt Lithium zu etwa gleichen Teilen in 1- un...
TL;DR: Aryl vinyl sulfones selectively react with thiol groups to acid-stable compounds which easily are cleaved by mild bases to thiol compounds as mentioned in this paper, and are good protecting groups or labels in peptide chemistry.
Abstract: Aryl vinyl sulfones selectively react with thiol groups to acid-stable compounds which easily are cleaved by mild bases to thiol compounds. Ester and amide groups are not attacked under these conditions. Therefore, these compounds are good protecting groups or labels in peptide chemistry. The following aryl vinyl sulfones were investigated: phenyl vinyl sulfone 1, p-carbethoxyphenyl vinyl sulfone 15 and the fluorescent 5-dimethylaminonaphthyl 1-vinyl sulfone 5 and 5-methoxynaphthyl-1 vinyl sulfone 10. The last two compounds are very useful reagents for the quantitative determination of SH-groups in polypeptides such as enzymes. Aryl-vinylsulfone reagieren selektiv mit Thiolgruppen zu Verbindungen, die saurestabil sind, aus denen aber unter milden basischen Bedingungen die Thiolverbindung wieder freigesetzt werden kann. Ester- und Amidbindungen werden nicht angegriffen, so das die Anwendung in der Peptidchemie moglich ist. Untersucht werden die Reaktionen von Phenylvinylsulfon 1 sowie p-Carbethoxy...
TL;DR: Some aspects of the reactivity of disphosphene are described, particularly reduction (LiAlH4), electrophilic additions (HCl, Cl2), heterocyclisation reactions (S8) as discussed by the authors.
Abstract: Some aspects of the reactivity of disphosphene RP[dbnd]PR 1 (R [dbnd] (Me3Si)3C) are described, particularly reduction (LiAlH4), electrophilic additions (HCl, Cl2), heterocyclisation reactions (S8). The very bulky (Me3 Si)3C group well stabilizes the adducts RP(H)P(H)R 5, RP(H)P(Cl)R 6, RP(H)Cl 7, RP(Cl)P(Cl)R 8, 11 such compounds being often unstable. Structure of 1 was determined by single crystal X-ray diffraction. 1 crystallizes in the triclinic space group; two independent centro-symmetric molecules are present in the unit cell, one of them shows a disorder at the level of silicon atoms; the P[dbnd]P bond lengths are respectively 2.003(3) and 2.001(3) A. Data are listed in Tables I to IV. All other crystallographic data are deposited with the Cambridge Crystallographic Data Centre (CCDC). Quelques aspects de la reactivite du diphosphene RP[dbnd]PR 1 (R [dbnd] (Me3Si)3C) sont presentes, en particulier des reactions de reduction (LiAlH4), d'additions electrophiles (HCl, Cl2) et d'heterocyclisa...
TL;DR: Several methods for the preparation of organobromophosphanes from RPCl2 and R2PCl by halogen exchange are described in this article, where the optimal results are obtained by equilibration of the chlorophosphane with PBr3 followed by distillation or crystallization.
Abstract: Several methods for the preparation of organobromophosphanes from RPCl2 and R2PCl by halogen exchange are described. In case of aryl compounds optimal results are obtained by equilibration of the chlorophosphanes with PBr3 followed by distillation or crystallization, while gaseous HBr proved to be most efficient for converting the alkyl phosphanes. The isomeric composition of X[sbnd]C6H4PCl2 (X [dbnd] F,Cl,Br,CH3O,(CH3)2N) obtained by Friedel-Crafts reaction is investigated by 31P-NMR. Pure p[sbnd]Cl[sbnd]C6H4PBr2 and p[sbnd]Br[sbnd]C6H4PBr2 can be isolated from the isomeric mixture by crystallization. Verschiedene Methoden zur Darstellung von Organobromphosphanen aus RPCl2 und R2PCl durch Halogenaustausch werden beschrieben. Im Falle der Arylverbindungen liefert die Aquilibrierung der Chlorphosphane mit PBr3 bei anschliesender Destination oder Kristallisation die besten Ergebnisse, wahrend die Umwandlung der Alkylphosphane zweckmasigerweise mit Bromwasserstoffgas erfolgt. Die isomere Zusammenset...
TL;DR: In this paper, mixed chloride dialkyldithiophophosphates of bismuth(III), [(RO)2PS2] n BiCl3-n (n = 1, 2; R [dbnd] Et, Pr n, Pr i and Bu i ) have been synthesized for the first time by the reactions of Bismuth trichloride with sodium diisopropyldithIophosphate or alternatively by co-disproportionation reactions of SDS in different stoichiometric ratios in suitable organic solvents.
Abstract: Mixed chloride dialkyldithiophosphates of bismuth(III), [(RO)2PS2] n BiCl3-n (n = 1, 2; R [dbnd] Et, Pr n , Pr i and Bu i ) have been synthesized for the first time by the reactions of bismuth trichloride with sodium diisopropyldithiophosphate or alternatively by co-disproportionation reactions of bismuth trichloride with bismuth tris(dialkyldithiophosphates) in different stoichiometric ratios in suitable organic solvents. Monohalobismuth bis(diisopropyldithiophosphates) have also been synthesized by the cleavage reactions of bismuth tris(dialkyldithiophosphates) with bromine or iodine in 2:1 molar ratio. These new derivatives have been characterized by elemental analysis, molecular weight determinations (both cryoscopic and ebullioscopic) as well as spectroscopic (IR, 1H NMR and 31P NMR) studies. On the basis of these data chelated structures with bidentate dialkyldithiophosphate groups have been proposed for these monomeric derivatives. Hydrolysis reactions of some of these compounds have also ...
TL;DR: In this article, the four electron cation P+ being complexed by two Ph3P was used to obtain a hexaphenyl triphosphenium tetrachloroaluminate.
Abstract: Reduction of PCl3 e.g. with trialkyl phosphines produces the well-known but ill-defined insoluble, amorphous, orange material approximating a phosphorus subchloride. In repeating this reduction with Ph3P and with AlCl3 as a third component we now obtained crystalline hexaphenyl triphosphenium tetrachloroaluminate. It may be thought to derive from the four electron cation P+ being complexed by two Ph3P.
TL;DR: In this article, LiP(SiMe3)2 was found to be such a versatile reagent that it can be used to elucidate synthesis and chemical behaviour of LiP[P[Me3Si2P]2]2.
Abstract: Our investigations to be presented here have their origin in a number of former results: The formation of [(Me3Si)2P]2SiMe2 [1] and its rearrangement to P4(SiMe2)6 (a molecule with adamantane structure) and P(SiMe3)3, the formation of P7(SiMe3)3 and of some cyclic phosphanes by the thermally induced rearrangement of [(Me3Si)2)P]2SiMe2 [3], and the formation of P7(SiMe3)3 by reacting P4 with Na/K-alloy and Me3SiCl. After finding LiP(SiMe3)2 to be such a versatile reagent we turned to elucidate synthesis and chemical behaviour of LiP[P(SiMe3)2]2.
TL;DR: In this paper, the initial process may involve one-electron transfer from the sulfide to the intermediate oxometalloporphyrin followed by coupling of two resulting charged products, and/or nucleophilic attack of sulfide on oxometaloporphrin oxygen, and the overall reactions are depicted by paths with different electron demands from the results of Hammett plots.
Abstract: Various sulfides are easily oxidized selectively to the corresponding sulfoxides in quantitative yields by iodosylarene (ArIO) catalyzed by metalloporphyrin (TPPM(III)Cl (M [dbnd] Fe, Mn)). The oxidation system is demonstrated to be a possible model for monooxygenase in the study of the stereochemistry of these sulfoxides. Metalloporphyrin-iodosylarene can initially equilibrate with the oxometalloporphyrin (TPPM(V)=O·Cl) formed in situ. The initial process may involve one-electron transfer from the sulfide to the intermediate oxometalloporphyrin followed by coupling of two resulting charged products, and/or nucleophilic attack of sulfide on oxometalloporphyrin oxygen. The overall reactions are depicted by paths with different electron demands from the results of Hammett plots.
TL;DR: In this article, a series of variously substituted sulfones has been synthesized by oxidation of the corresponding sulfides with the hydrogen peroxide/selenium dioxide system, and very short reaction time, easy work-up and high yields make this new preparation of sulfones a recommendable method.
Abstract: A series of variously substituted sulfones has been synthesized by oxidation of the corresponding sulfides with the hydrogen peroxide/selenium dioxide system. Very short reaction time, easy work-up and high yields make this new preparation of sulfones a recommendable method.
TL;DR: In this article, a few 2-pyridyl sulfoxides were found to work as phase-transfer catalysts for some typical nucleophilic reactions in nonpolar solvents such as benzene, and in two-phase systems such as a benzene-water.
Abstract: Several 2-pyridyl sulfides (1) (e.g., methyl (1a), ethyl (1b), isopropyl (1c), benzyl (1d), 1-phenylethyl (1e), l-menthyl (If) 2-pyridyl sulfides; and bis(2-pyridylthio)methane (1g), and methyl 2-(N-oxy-pyridyl) sulfide (1h) were prepared by the usual method. Sulfoxides (2) were prepared by oxidation of the corresponding sulfides with m-chloroperbenzoic acid in good yields. A few sulfoxides were found to work as phase-transfer catalysts for some typical nucleophilic reactions in nonpolar solvents such as benzene, and in two-phase systems such as benzene-water. S-2-Pyridyl-N-(p-toluenesulfonyl) sulfilimines (3) were prepared upon treatment of sulfides with Chloramine-T. Hydrolysis of N-(p-toluenesulfonyl)-2-pyridyl-o-tolylsulfilimine (3i) with conc. sulfuric acid gave the corresponding free sulfilimine in a moderate yield. S-2-Pyridyl sulfoximines (4) were not obtained by the general method from the sulfoxides and hydrazoic acid. Alkyl-2-pyridyl sulfoximines, however, were obtained by oxidation of...
TL;DR: In this article, the preparative and derivative chemistry of silylated (methylene)phosphines including (Me3Si)2NP[dbnd]CHSiMe3, MesP[DBnd]C(SiMe 3)2, and a stable 1-phosphadiene system is reported.
Abstract: The preparative and derivative chemistry of several silylated (methylene)phosphines including (Me3Si)2NP[dbnd]CHSiMe3, MesP[dbnd]C(SiMe3)2, and a stable 1-phosphadiene system is reported.
TL;DR: In this paper, the triaryl-phosphines ArPPh2, Ar2PPh and Ar3P were synthesized using the Tolman-rule for ortho-lithiated arylalkylethers.
Abstract: Alkylphenylethers, ortho-lithiated in good yields, are transformed according to scheme (1) to the triaryl-phosphines ArPPh2, Ar2PPh and Ar3P (Ar contains in all cases an ortho-alkoxy group) (Table 1). Hydroquinonedialkylethers can be lithiated twice, forming the compounds 102 and 103. Table 2 summarizes some arylalkylethers (71-101) which were lithiated; table 7 presents 12 new arylalkylethers. The syntheses of triarylphosphines with one or two bulky groups (105-110) and of triaryl-phosphines with one or two 3,4-dialkoxyphenyl groups (111-114) are reported. The 31P-spectra of the compounds prepared are discussed with respect to the validity of the Tolman-rule. Alkylphenylether werden in guten Ausbeuten ortho-lithiiert und nach (1) in die Triarylphosphine ArPPh2, Ar2PPh und Ar3P uberfuhrt. (Ar enthalt immer eine ortho-standige Alkoxygruppe) (Tabelle 1). Bei Hydrochinondialkylethern werden auch Zweifachlithiierungen beobachtet, 102 und 103. Tabelle 2 zeigt die zur Lithiierung hergestellten Arylalky...
TL;DR: In this article, structural data of phosphorus ylides are summarized and discussed, as well as NMR spectroscopy and X-ray diffraction results indicate a strong gauche effect for the lone pairs of electrons at the ylidic carbon atom.
Abstract: Structural data of phosphorus ylides are summarized and discussed. Conformational preferences in solution and in the solid state, as followed by NMR spectroscopy and X-ray diffraction, indicate a strong gauche effect for the lone pairs of electrons at the ylidic carbon atom. One- and two-electron oxydation of ylide carbanions is accomplished with copper(II) as the oxidant, leading to oxidative coupling or to halogenation, respectively.
TL;DR: Alkyl- or arylbis(trimethylsilyl)phosphines and corresponding arsines react with acyl chlorides to give [1]-phosphine 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature as discussed by the authors.
Abstract: Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones.1
TL;DR: In this article, the synthesis, chemical, and spectral properties of (3-amino-3-hydroxy carbonyl-propyl)phosphonous acid (2), bis(3amino-, 3-hydroxylcarbonylpropyl)-phosphinic acid (5), (2-amide-2-hydrocarbonylethyl)-methyl-phosphinothricin (2, 5, 8, 10, and 12, showed no activity as herbicides.
Abstract: The synthesis, chemical, and spectral properties of (3-amino-3-hydroxycarbonyl-propyl)phosphonous acid (2), bis(3-amino-3-hydroxycarbonylpropyl)phosphinic acid (5), (2-amino-2-hydroxycarbonylethyl)-methyl-phosphinic acid (6), (1-amino-2-hydroxycarbonylethyl)methylphosphinic acid (10), and of a structural isomer of phosphinothricin, (3-amino-2-hydroxycarbonylpropyl)-methylphosphinic acid (12) are described. While the phosphonous acid derivative 2 exhibited weak herbicidal activity, the acids 4, 5, 8, 10, and 12, showed no activity as herbicides. The phosphinic acid 12 showed weak plant growth regulator properties.
TL;DR: In this article, the el-mass spectra (70 eV) of dithiophosphinic acids R2P(S)SH (R: CH3, C2H5, n-C3H7, N-C4H9, CH2[dbnd]CH, C6H5.
Abstract: El-mass spectra (70 eV) of dithiophosphinic acids R2P(S)SH (R: CH3, C2H5, n-C3H7. n-C4H9, CH2[dbnd]CH. C6H5, p-CH3OC6H4, P-CH2[dbnd]CHC6H4) are reported and discussed. All spectra show abundant molecular ions, which decompose by α-fission under loss of SH' and formation of abundant ions [R2PS]+. Loss of R is not observed. In the case of the aliphatic compounds, however, increasing fragmentation of R occurs with growing chain length of these substituents. In this process fragment ions [RPS2H2]+. are formed in a first step after elimination of (R—H) and H-migration. Thereupon olefin is eliminated again under formation of [H3PS2]+. (m/z 98). With the aromatic compounds the appearance of [RSH]+., resulting from migration of R from phosphorus to sulfur and elimination of RPS, should be mentioned. General fragmentation patterns, which are in accordance with B/E-linked scans, are given. EI-Massenspektren (70 eV) von Dithiophosphinsauren R2P(S)SH (R: CH3, C2H5, n-C3H7, n-C4H9, CH2[dbnd]CH, C6H5, p-CH3OC6...
TL;DR: In this paper, it was shown that the partial polymerization of liquid sulfur which occurs on heating to temperatures above 159°C is initiated by free radicals originating from the homolytic dissociation of the cyclic molecules S6 and S7 whose first dissociation enthalpies are calculated from thermodynamic data as 124 and 127 kJ/mol, respectively.
Abstract: It is shown that the partial polymerization of liquid sulfur which occurs on heating to temperatures above 159°C is initiated by free radicals originating from the homolytic dissociation of the cyclic molecules S6 and S7 whose first dissociation enthalpies are calculated from thermodynamic data as 124 and 127 kJ/mol, respectively.
TL;DR: The absolute configurations of optically active phosphonic analogues of serine, β-chloroalanine, phenylalanine and tyrosine have been established via chemical correlations with alanine or aspartic acid of known configuration as discussed by the authors.
Abstract: The absolute configurations of optically active phosphonic analogues of serine, β-chloroalanine, phenylalanine, tyrosine and 2-aziridinephosphonic acid have been established via chemical correlations with phosphonic analogues of alanine or aspartic acid of known configuration.
TL;DR: In this paper, 2,8-Dioxa-5-aza-1-phosphabicyclo[3.3.0] octane, 1, and 2,10-dioxa -6-aza 1-phophosphabicylo[4.4] decane, 2, both react with diethyl peroxide to give phosphoranes containing two ethoxy groups.
Abstract: 2,8-Dioxa-5-aza-1-phosphabicyclo[3.3.0] octane, 1, and 2,10-dioxa-6-aza-1-phosphabicyclo[4.4.0] decane, 2, both react with diethyl peroxide to give phosphoranes containing two ethoxy groups. The reactivities of 1 and 2 towards diethyl peroxide are very different. The reaction of 1 at 0°C in methylene chloride is complete after 7 days whereas 2 and diethyl peroxide in methylene chloride require 30 days at room temperature for 89% reaction. The opposite reactivity of 1 and 2 are found in their reactions with diphenyl disulfide. These data strongly support a direct insertion by phosphorus into the oxygen-oxygen bond of the peroxide. Compounds, 1 and 2 were allowed to react with trifluoroethoxy benzenesulfenate and 1,1,1,3,3,3-hexafluoroisopropoxy benzenesulfenate. Dioxyphosphoranes were formed in all cases. The structures of these materials are discussed. Products of condensation reactions of 1 and 2 were also obtained and structural features are noted.
TL;DR: In this article, the mechanism of substitution reactions at tricovalent phosphorus, mainly the system, is discussed on the basis of stereochemistry, catalysis, kinetics and substituent effects.
Abstract: The mechanism of substitution reactions at tricovalent phosphorus, mainly the system , is discussed on the basis of stereochemistry, catalysis, kinetics and substituent effects.