Ethylene polymerization reactions with Ziegler–Natta catalysts. I. Ethylene polymerization kinetics and kinetic mechanism

Kinetics of ethylene homopolymerization reactions and ethylene/1-hexene copolymerization reactions using a supported Ziegler–Natta catalyst was carried out over a broad range of reaction conditions. The kinetic data were analyzed using a concept of multicenter catalysis with different centers that respond differently to changes in reaction parameters. The catalyst contains five types of active centers that differ in the molecular weights of material they produce and in their copolymerization ability. In ethylene homopolymerization reactions, each active center has a high reaction order with respect to ethylene concentration, close to the second order. In ethylene/α-olefin copolymerization reactions, the centers that have poor copolymerization ability retain this high reaction order, whereas the centers that have good copolymerization ability change the reaction order to the first order. Hydrogen depresses activity of each type of center in the homopolymerization reactions in a reversible manner; however, the centers that copolymerize ethylene and α-olefins well are not depressed if an α-olefin is present in the reaction medium. Introduction of an α-olefin significantly increases activity of those centers, which are effective in copolymerizing it with ethylene but does not affect the centers that copolymerize ethylene and α-olefins poorly. To explain these kinetic features, a new reaction scheme is proposed. It is based on a hypothesis that the Ti—C₂H₅ bond in active centers has low reactivity due to the equilibrium formation of a Ti—C₂H₅ species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4255–4272, 1999     

α-乙酰基二硫缩烯酮α碳原子的酰化反应

进行了α-乙酰基二硫缩烯酮与酰氯的酰化反应. 以干燥的二氯甲烷为溶剂, 在四氯化钛催化下, α-乙酰基环二硫缩烯酮(1)可与脂肪及芳酰氯(2)反应, 在化合物1的α-碳原子上发生酰化反应, 以较高的产率生成各种α-乙酰基-α-酰基二硫缩烯酮(3).     

Novel Rearrangements and Heterocyclisation of P-Imides

Abstract

The preliminary introduction of electron accepting dichlorophosphine group at nitrogen atom of N-monosub-stituted α-aminoketones or α-aminocarbon acid esters increases the mobility of the α-carbon hydrogen atom so, that the intermolecular O-phosphorylation is enabled.¹     

MECHANISM OF THE REACTION OF DIPHENYL N-BROMOSULFILIMINE WITH SULFIDES,PHOSPHINES AND TERTIARY AMINES

Abstract

The mechanism of the reactions of diphenyl N-bromosulfilimine (I) with such nucleophiles as sulfides, phosphines and tertiary amines was investigated. In the presence of water, (I) reacts with sulfides or phosphines to afford the corresponding sulfoxides or the phosphine oxides in moderate yields; however, the reaction with tertiary amine gave only the N-t-aminosulfilimine derivative. The effect of ring size in the reaction with cyclic sulfides suggests that the reaction proceeds via initial bromine transfer from the nitrogen atom to the sulfur atom of the cyclic sulfides followed by S_N2 type substitution of bromide on the sulfur atom of the cyclic sulfide with the sulfilimino group. The phosphine oxide obtained in the reaction of (I) with optically active methyl n-propyl phenyl phosphine was racemized but retained a small portion of the optical activity. In the case of tertiary amines, even 1,4-diazabicyclo-(2,2,2)-octane (DABCO), in which the back side of the nitrogen atom is blocked, reacted smoothly to afford the corresponding ammonium salts, suggesting the reaction to be of S_N2 type on the nitrogen atom of the sulfilimine.     

O−• chemical ionization of carbonyl compounds

The negative ion chemical ionization mass spectra of twentyeight C₄ to C₇ carbonyl compounds were recorded using the oxide radical anion O^?? as reagent ion. As noted earlier, the reactions occurring include H⁺ abstraction, H ₂ ^+? abstraction, H? atom displacement, and alkyl radical displacement. In addition, the [M?2H]^? ions fragment further by alkyl radical elimination. The relative importance of these reactions depends strongly on molecular structure, with the result that isomer distinction frequently is possible. Where this is not possible, as for isomeric aldehydes, the collisional charge inversion mass spectra of common product ions provides isomer distinction. The H ₂ ^+? abstraction reaction is shown to involve abstraction not only of two hydrogens from the same α-carbon but also, in part, abstraction of one hydrogen from each α-carbon.     

Skeletal rearrangement of a bicylic 1,3-diphenyltrisilane during acid-induced dephenylation reactions

Protic and Lewis acid-induced dephenylation reactions of bis(tetramethylene)-tethered bicyclic 1,3-diphenyltrisilane 1 have been found to be accompanied by a facile skeletal rearrangement that forms the ring-contracted silyl-substituted bicyclic disilanes. For the reaction with a protic acid (HX), such as HCl/AlCl₃ and trifluoromethanesulfonic acid (TfOH), the protonation of the ipso-carbon of the phenyl group would be followed by the nucleophilic attack of X⁻ on the central silicon atom that induces the skeletal rearrangement. In the case of the reaction with boron trichloride, the same rearranged product was obtained as well, although the reaction mechanism is not clear. Dedicated to Professor Mitsuo Kira on the occasion of being awarded the 2005 Wacker Award and in recognition of his outstanding contribution to silicon chemistry.     

Regioselective acetylation of some N-methylpyrrole derivatives with isopropenyl acetate and different acetic anhydrides

We studied the reactions of some N-methylpyrrole derivatives with isopropenyl acetate and different acetic anhydrides. We have found that the reaction with isopropenyl acetate afforded 5-acetylpyrrole derivatives while with acetic anhydrides acetylation occurred on the α-carbon atom of the side-chain of pyrrole-2-acetic acid derivatives.     

REACTIONS OF ARSINIC AND ARSONIC ACIDS WITH H2S AND H2Se: CRYSTAL STRUCTURE OF 1,4-DIPHENYL-1,4-DIARSA-2,3,5-TRISELENACYCLOPENTANE

Abstract

The reactions of a series of arsinic and arsonic acids with hydrogen sulfide and hydrogen selenide have been investigated. The various arsinic acids were found to produce a variety of products, but the reaction was characterized by the reduction of arsenic(V) to arsenic(III), loss of hydroxyl groups bonded to arsenic and, to a lesser degree, the rupture of arsenic-carbon bond(s). Phenylcarboxymethylarsinic acid yielded, on reaction with H₂S or H₂Se, 1,4-diphenyl-1,4-diarsa-2,3,5-trichalocogenapentanes, where the chalcogen atom is S or Se. Arsonic acids yielded as final products compounds having a range of stoichiometries ranging from RAsS to R-7As₂S₃. 1,4-Diphenyl-1,4-diarsa-2,3,5-triselenacyclopentane consists of a non-planar, five-membered ring in which the As–C bond distances are 1.962 Å, the As—Se bond distances are 2.388 Å and the Se—Se bond distance is 2.334 Å. The bond distances are very close to those which are expected for single, covalent bonds.     

Aldol condensation of amides using phosphazene-based catalysis

We have developed a new method for the direct aldol condensation of unactivated amides using 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-hexachloride (TAPC)-based phosphorous/SO₄²⁻ catalysis. The SO₄²⁻ species in a reaction mixture enhances the reaction rate of the catalysis. In principle, no metal sources are required for the generation of the catalyst, and there is no requirement for the use of stoichiometric quantities of an acid or base. This catalyst system is operative under relatively acidic conditions. One major advantage of carrying out the reaction under acidic conditions is that both aldehydes and acetals are capable of undergoing carbon-carbon bond formation at the α-carbon of amide carbonyl groups through dehydration.     

Halogenotropy in Phosphorus-Carbon Diad

Abstract

NMR and chemical studies have shown that α-halogenoalkyl-phosphines 1 and P-halogenoylids 2 exist as halogenotropic tautoineric systems. The position of the equilibrium depends on the used solvent, temperatures and substituents at the α-carbon atom. For example, the equilibrium 1 2 shifts towards the phosphine from 1 if the substituents at the α-carbon atom are electron-donating (R = H, Me, Pr, i-Pr). These compunds, existing preferably in the phosphine form, undergo typical reactions both for tervalent phosphorus compounds and P-halogenoylids. Tervalent phosphorus compounds, α-halogenoalkylphosphines 1 add sulfur and react with anhydrous HCl to convert into the dichlorophosphines -4. Like the P-halogenoylids, they add alcohols and phenols forming the phosphonium salts 5, 6, react with primary amines and aniline to yield the iminophosphonates 7 They also form the 2-halogenoalkylphosphonates 8 in the reaction with aldehydes.     

Cross-aldol reactions of levoglucosenone and its derivatives with cyclohex-1-en-1-ol ethers

The reaction of levoglucosenone with cyclohex-1-en-1-yl trimethylsilyl ether under Mukaiyama reaction conditions gave [1 + 2]-Michael–aldol condensation product with participation of the acetal center. The reaction was accompanied by opening of the 1,6-anhydro bridge and intramolecular hemiketalization by the hydroxy group of the 2-oxocyclohex-1-enyl fragment. Under analogous conditions, dihydrolevoglucosenone gave rise to four diastereoisomeric 1,2-addition products. Internal cyclohex-1-en-1-ol ether obtained by treatment of the Michael adduct of levoglucosenone and cyclohexanone with Ac₂O–ZnCl₂ underwent intramolecular Mukaiyama reaction involving substituted α-carbon atom of the cyclohexanone fragment and acetal moiety to afford spiro derivative and product of subsequent AdE1 acetylation of intermediate α′-cyclohexenyl ether fragment.     

ORGANISCHE PHOTOCHEMIE XXXII1,2

Abstract

Es werden drei neue Beispiele zu Photoreaktionen von Aroyl-diphenylphosphinen beschrieben, die sowohl unter α-Spaltung als auch 1.2-Sauerstoff-Transfer aus der Carbonylgruppe auf den Phosphor verlaufen. Beide Reaktionen finden auch im Massenspektrometer statt.

Three new examples to photoreactions of aroyl diphenyl phosphines which undergo α-cleavage as well as 1.2-oxygen transfer from the carbonyl group onto the phosphorous atom are described. Both reactions also occur in the mass spectrometer.     

A C-C bond formation reaction at the α-carbon atom of α-oxo ketene dithioacetals via the Baylis-Hillman type reaction

The first example of TiCl₄-mediated Baylis-Hillman type reaction of α-acetyl cyclic ketene dithioacetals with arylaldehydes was described. This methodology adds a new entry to the C-C bond formation at the α-carbon atom of α-oxo ketene dithioacetals.     

THE EFFECT OF OXYGEN ON THE INCORPORATION OF MANGANESE,IRON AND COBALT INTO HEMATOPORPHYRIN IX IN GLACIAL ACETIC ACID

Abstract

The results of polarography studies for the reaction of hematoporphyrin IX with Mn(II), Fe(II) and Co(II) ion in acetic acid in the absence and the presence of oxygen are reported. The metal incorporation reaction in the presence of oxygen is quantitative for Mn and Co and incomplete for Fe. In the absence of oxygen, the Mn reaction does not proceed at all, whereas, both the Fe and Co reactions are quantitative.     

Silver-Catalyzed Asymmetric Insertion into Phenolic O−H Bonds using Aryl Diazoacetates and Theoretical Mechanistic Studies

An enantioselective insertion reaction of silver carbenes generated from donor–acceptor-substituted diazo compounds into the O−H bond of phenols was developed. A homobinuclear silver complex with a chiral phosphorous ligand was created in situ from AgNTf₂ and (S)-XylylBINAP (in a 2:1 mole ratio). Detailed mechanistic studies using combined experimental and computational techniques revealed that one silver atom center of the catalyst forms a silver carbene and another one works as a Lewis acid for the nucleophilic addition of a phenol. Two counter-anions, two water molecules, and two silver atoms cooperatively mediate the subsequent protonation event to lower the activation energy and control enantioselectivity, affording an array of valuable α-aryl-α-aryloxy esters.     

STUDIES ON THE RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN Ⅳ. COPOLYMERIZATION OF TETRAHYDROFURAN AND PROPYLENE OXIDE INITIATED BY FUMING SULFURIC ACID AND PERCHLORIC ACID CATALYST SYSTEM

The yield of copolymerization of tetrahydrofuran and propylene oxide (THF:PO=100:5—15, by wt.) using a binary catalyst of fuming sulfuric acid (21% or 28%) and perchloric acid is around 50—60%, and the loss of THF in the reaction is below 10—15%. The average molecular weight of the product can be controlled in the range of 1000—2000 by varying the binary catalyst system. The present method, which is different from the usual copolymerization initiated by BF_3-diol or SbCl_5-diol system, shows the pecularities i.e. the yield of copolymerization with the low PO feed is not decreased, the hydroxyl functionality is equal to 2, and the end-groups are predominantly primary hydroxyls (around 65—70%).     

Enzymatic resolution of α-hydroxyphosphinates with two stereogenic centres and determination of absolute configuration of stereoisomers obtained

The use of quinine as a chiral solvating agent allows us to determine a tentative absolute configuration at the phosphorus atom of hydroxyphosphinates with two stereogenic centres (at the phosphorus and α-carbon atoms). Two ethyl butyryloxyalkane(P-phenyl)phosphinates were hydrolysed using various lipases. In all cases isomers possessing α-carbon atom with an (S)-configuration were hydrolysed preferentially. The absolute configuration of both chiral centres of obtained α-hydroxyphosphinates was determined by using (S)-(+)-MTPA-Cl and quinine. The mode of chiral discrimination of α-hydroxyphosphinates by quinine was studied by means of computational chemistry, which confirmed the experimental findings that the signals in ³¹P NMR spectra of compounds with an (R_P)-configuration are situated upfield when compared with the respective (S_P) isomers.     

PREPARATION AND PROPERTIES OF PYRIDINE DICARBOXYLIC ACID COMPLEXES OF THE LANTHANIDES

Abstract

The preparation and spectroscopic properties of eleven hydrated lanthanide (III) dipicolinate and quinolinate complexes are reported for the first time. The complexes are of three general types: M(dipi)(dipiH)(H₂O)₄, M(dipiH)₃(H₂O) and M(quin)(quinH)(H₂O)₃ [where M =lanthanide (III); dipiH₂ =pyridine-2,6-dicarboxylic acid (dipicolinic acid); quinH₂ =pyridine-2, 3-dicarboxylic acid (quinolinic acid)], and evidence is presented which indicates that they may be six-coordinate.     

CATALYTIC EFFECTS IN THE AMINOLYSIS REACTIONS OF ARYLSULPHONIC ACID DERIVATIVES IN NON-AQUEOUS MEDIA

Abstract

The catalytic effects of organic bases in reactions of arylamines with arylsulphonic acid derivatives, ArSO₂X (X = Cl, Br, OSO₂Ar) in aprotic media are characterised by the following regularities. 1. The activity of 3- and 4-substituted pyridines, N-alkyl- and N-phenylimidazoles is desribed by the common Bränsted relationship. Substituents in positions 2 and 2,6 of the pyridine molecule have a strong steric influence. Tertiary cyclic amines of quinuclidine type with the same basicity as pyridines and imidazoles have more higher activity than the latter. N-Oxides of pyridine which are 4–5 pK_a units less basic than the corresponding pyridines have the catalytic activity 100 times as much, as compared with them. 2. The intensity of the catalytic action of pyridines and their N-oxides alters insignificantly with changing the leaving group X in the substrate, somewhat increasing in the order Cl < Br≤OSO₂Ar. 3. The activity of pyridine bases increases with increasing the solvent solvating ability. The inhibiting influence of the X^? anione on the rate of catalytic reaction displays in media of high polarity (nitrobenzene, acetonitrile). These regularities are explained in terms of the nucleophilic mechanism of catalysis which is supported by isolating intermediate adducts of tertiary amines (in particular 4-N,N-dimethylaminopyridine) with arylsulphonic acid bromides and anhydrides and by studies of their reactivity towards arylamines in methylene chloride. Compounds of bifunctional nature (carboxylic acids) do not accelerate the reaction under consideration unlike a similar substitution process at the carbonyl C-atom. The cause of this seems to be a different geometry of transition states in substitution at the sulpho group S-atom and at the carbonyl carbon, respectively.     

ORGANOPHOSPHORUS COMPOUNDS AS POTENTIAL FUNGICIDES. PART I. N-(ω-GUANI-DINOALKYL)AMINOALKANEPHOSPHONIC ACIDS AND THEIR AMINOPHOSPHONIC PRECURSORS: PREPARATION,NMR SPECTROSCOPY,AND FAST ATOM BOMBARDMENT MASS SPECTROMETRY

Abstract

N-(ω-Aminoalkyl)- and N-(ω-guanidinoalkyl)-aminoalkanephosphonic acids have been prepared from α, ω-diaminoalkanes by reaction with chloromethanephosphonic acid (or an ester of a halogeno-alkanephosphonic acid), followed by treatment with S-methylisothiouronium chloride. Ethylene diamine yielded 1-phosphonomethyl-2-iminoimidazolidine. A number of 1:1 salts of the α, ω-diamines and chloromethanephosphonic acid are also reported. Doubly charged zwitterionic structures are assigned to both ω-amino and ω-guanidino compounds on the basis of ³¹P and ¹³C nmr data. Thus the addition of an excess of acid (D₂SO₄) causes the ³¹P chemical shift to move to higher field, from ca. 8 to 14 ppm, whilst ¹ Jpc increases from ca. 130 to 150 Hz. The ¹H and ¹³C chemical shifts of the terminal methylene groups in the polymethylene chain are unaffected by acidification.

Fast atom bombardment mass spectrometry gives rise to characteristic [M + H]⁺ ions, frequently as the base peak, and to fragmentations involving the loss of phosphorous acid, or the formation of ions resulting from carbon-nitrogen or carbon-carbon cleavage. The compounds show activity against a number of fungal pathogens and other microbial organisms.