Showing papers on "Lewis acids and bases published in 1974"
204 citations
TL;DR: In the presence of molecular oxygen, each of the above complexes of Co(II) tetraarylporphyrins forms an oxygen adduct in which the unpaired electron appears to be localized on oxygen between 76 and 81 % of the time as mentioned in this paper.
73 citations
45 citations
41 citations
TL;DR: In this paper, it was shown that enol acetate reacts with various acetals and benzaldehyde to afford the corresponding aldol-type addition products in good yields in the presence of Lewis acid.
Abstract: It was found that, in the presence of Lewis acid such as TiCl4, AlCl3, SnCl4, ZnCl2, and BF3·O(C2H5)2, enol acetate reacts with various acetals and benzaldehyde to afford the corresponding aldol-type addition products in good yields.
38 citations
TL;DR: In this article, the donor-acceptor type RCXO→MXn is characterized by the formation of a coordinate oxygen-metal bond; the transfer of electrons from the oxygen to the metal of the acceptor is always due to a weak donoracceptor interaction.
Abstract: Addition compounds of Lewis acids MXn and acyl halides RCOX occur as intermediates in Friedel-Crafts acylations. IR and NMR studies on these intermediates have indicated the probable existence of structural isomers. In X-ray structural analysis, it is possible to distinguish two forms, i.e. the molecular form, in which the compounds are present as donor-acceptor complexes RCXO→MXn, and the ionic form, in which they can be formulated as oxocarbenium salts [RCO]+[MXn+1]−. The compounds of the donor-acceptor type RCXO→MXn are characterized by the formation of a coordinate oxygen-metal bond; the transfer of electrons from the oxygen to the metal of the acceptor is always due to a weak donor-acceptor interaction. The positive charge of the aryloxocarbenium ions is partly delocalized over the aromatic nucleus. The positive charge in alkyloxocarbenium ions, on the other hand, is essentially localized on the carbon atom of the carbonyl group, as is confirmed by electron density distribution calculations.
37 citations
37 citations
TL;DR: A variety of cyclopropylcarbinyl compounds have been prepared by cyclodestannylation reaction of alk-3-en-yltin compounds as mentioned in this paper.
35 citations
Patent•
04 Dec 1974TL;DR: An olefine polymerisation catalyst comprises a titanium trichloride component of high surface area, an organo-metallic component, a Lewis base component and optionally a polyene.
Abstract: An olefine polymerisation catalyst comprises a titanium trichloride component of high surface area, an organo-metallic component, a Lewis Base component and optionally a polyene. The TiCl 3 component which may have a high porosity is conveniently obtained by the reaction of TiCl 4 and an organo-aluminium compound, treating the reaction product with a complexing agent and then contacting this product with TiCl 4 . The organo-metallic component is preferably aluminium triethyl, the Lewis Base component hexamethylphosphoric triamide and the polyene is cycloheptatriene. This system has high polymerisation activity combined with good stereospecificity. Polypropylene can be obtained in high yield thereby giving low catalyst residues and the polymer has a high stiffness modulus.
33 citations
33 citations
TL;DR: In this paper, the nucleophilic cleavage of metal-metal bonds by phosphines was studied in arsine bridged dinuclear complexes, where the hetero-metal-metal bond can be cleaved by phosphine.
Abstract: IN arsinverbruckten Zweikernkomplexen last sich die Hetero-Metall-Metall-Bindung mit Phosphinen spalten. Aus Molekulen mit dem Baugerust
entstehen so die Verbindungen mit der Struktur Fe–As–Mn–P und Fe–As–Co–P.
Organometallic Lewis Bases, XIX. Nucleophilic Cleavage of Metal-Metal Bonds by Phosphines
In arsine bridged dinuclear complexes the hetero-metal-metal bond can be cleaved by phosphines. From molecules with the framework
thus compounds with the structure Fe–As–Mn–P and Fe–As–Co–P are obtained.
TL;DR: In this article, the authors examined the correlation between the acidic properties of catalysts and their activity or selectivity and elucidated the reaction mechanism, dehydration reactions of 4-methyl-2-pentanol and 2-butanol over Al2O3 poisoned with basic compounds were carried out at 80-250°C by means of the conventional flow method or a thermal desorption method.
Abstract: In order to examine the correlation between the acidic properties of catalysts and their activity or selectivity and to elucidate the reaction mechanism, dehydration reactions of 4-methyl-2-pentanol and 2-butanol over Al2O3, SiO2, SiO2–Al2O3, ZnS, NiSO4, Al2(SO4)3 or Al2O3 poisoned with basic compounds were carried out at 80–250°C by means of the conventional flow method or a thermal desorption method. The following results were obtained. 1) Both Bronsted and Lewis acids are active, the latter being so to a greater extent. 2) Even relatively weak acid catalysts of acid strength Ho=4.8–6.8 are active, the catalytic activity being correlated with the number of effective acid sites. 3) The selectivity of 4-methyl-1-pentene/4-methyl-2-pentene and 4-methyl-cis-2-pentene/4-methy-trans-2-pentene is lower for Bronsted acids than for Lewis acids and higher for weaker Lewis acid strengths. 4) The composition of butene isomers varies greatly with changes in desorption temperature and the amount of adsorbed 2-butanol...
TL;DR: In this article, NH 4 -clinoptilolite after deammoniation at 400 °C was shown to have a single hydroxyl band at 3620 cm −1, slightly asymmetric to the lower wave numbers.
Patent•
06 May 1974TL;DR: In this article, it was shown that graphite having the specified components intercalated in its structure is shown to be much more effective in hydrocarbon conversion, e.g., isomerization, than catalysts having said components deposited on the surface of the graphite.
Abstract: Hydrocarbon conversion is effected in the presence of a catalyst consisting essentially of graphite having intercalated in the lattice thereof between about 5 and about 75 weight percent of a Lewis acid. The catalyst may additionally have intercalated therein a minor proportion of a Bronsted acid and/or a Group VI-B or Group VIII metal. The catalyst of graphite having the specified components intercalated in its structure is shown to be much more effective in hydrocarbon conversion, e.g., isomerization, than catalysts having said components deposited on the surface of the graphite.
TL;DR: In the presence of 5% zinc chloride, phenyl β-D -glucopyranoside thermolysis was shown to be possible at relatively low temperatures and in two distinct stages as discussed by the authors.
TL;DR: In this article, it is suggested that the main effect of O 2 is to enhance the Lewis acidity of EtAlCl 2, so as to favor an electrophilic attack of the Lewis acids to the tungsten through the carbonyl ligand.
TL;DR: In this article, the reaction of furan and ethyl propiolate at 130° affords a low yield of 2,6-dicarbethoxy-9-oxatetracyclo[3.2.1.4]non-6-ene (4).
Abstract: Reaction of furan and ethyl propiolate at 130° affords a low yield of 2,6-dicarbethoxy-9-oxatetracyclo[3.2.1.1.3,802,4]non-6-ene (4). This structure was confirmed by 1H and 13C n.m.r. spectroscopy....
TL;DR: Polarized Raman spectra in methylene chloride have been obtained for a number of complexes of the type LM(CO)5 (L = Lewis base; M = Cr, W) in the region 100−680 cm−1.
TL;DR: In this article, the reactions of dicobalt octacarbonyl with halides of the main Group III elements are described, and the reaction results in the derivatives GaCo2 Br4(CO)4(THF)2 and GaCoCo2Br4( CO)4L4 (L = phosphine, H2O).
TL;DR: In this paper, the behaviour of the basicity indicator ions Tl +, Pb 2+ and Bi 3+ was studied in model glasses having anion compositions: chloride-sulfate, bromide-Sulfate and chloride-bromide.
TL;DR: In this article, it was shown that propargylic tin compounds can exist in equilibrium with their allenic isomers and that this tautomeric equilibrium is not spontaneous but must be catalysed by electron-donor solvents or by Lewis acids.
TL;DR: The reaction of [RhCl(CO) 2 ] 2 with tricyclohexylphosphine oxide (Cy 3 PO) (Rh/Cy 3PO molar ratio 1) gives the dicarbonyl derivative, cis-[RhClCl( CO) 2 (Cy3 PO)], which is stable toward loss of carbon monoxide and subsequent dimerization as discussed by the authors.
TL;DR: In this article, the NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability.
Abstract: 13C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β-carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α-carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl3 > EtAlCl2 > Et1.5AlCl1.5 > Et2AlCl > SnCl4, EtOAlCl2 > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism.
TL;DR: In this article, the synthesis of N,N-disubstituted benzhydrazidoyl chlorides and their reaction with cyano compounds in the presence of a Lewis acid are described.
TL;DR: In this paper, the infrared spectra of diethylcadmium (CdEt2) in a variety of different solvents were measured and linear relationships were observed for the plots of the two frequency shifts Δνa(C−Cd−C) of Cd Et2 vs. Δνα(Zn−C)-Cd −C) and Δα(O−D−D) of CH3OD.
Abstract: The infrared spectra of diethylcadmium(CdEt2) in a variety of different solvents were measured. The affinity of CdEt2 toward oxygen and sulfur bases was studied by infrared frequency shifts of CdEt2. Linear relationships were observed for the plots of the two frequency shifts Δνa(C–Cd–C) of CdEt2 vs. Δνa(C–Zn–C) of ZnEt2 and Δνa(C–Cd–C) vs. Δν(O–D) of CH3OD. The deviation of the plots for the systems of CdEt2 with cyclic sulfides from the linear behavior was interpreted in terms of dative back-bonding from CdEt2 to sulfides. The enhanced reactivity of the Cd–S compound toward propylene oxide compared to that of the Cd–O compound was considered to result from a harder acid character of the Cd atom in the Cd–S compound caused by its back-bonding nature.
TL;DR: In this article, a slow proton transfer mechanism was proposed for the esterification of olefins in CH 3 CO 2 H or CH 3 ) CO 2 H with carboxylic acids.
Patent•
21 Jun 1974TL;DR: In this paper, a 2,2,6, 6,6-Tetramethyl-4-oxopiperidine is prepared from 2.2,4, 4, 6-pentamethyl-2,3, 4.5-tetrahydropyrimidine by treatment with an acidic catalyst.
Abstract: 2,2,6,6-Tetramethyl-4-oxopiperidine is prepared from 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine by treatment with an acidic catalyst. Suitable catalysts are Lewis acids, protonic acids and their salts with ammonia or organic bases. The reaction may be carried out in organic solvents, preferably in acetone, by gentle heating, for example at 40° to 65°C. Yields of 95% are obtainable after a reaction of several hours.
TL;DR: Plemek et al. as mentioned in this paper proposed a general stability rule for nidocarboranes based on an intercomparison of various nido-carboranes with other members of this family.
Abstract: The formation of several nido-carboranes, their structures, chemistry, some comparisons with nido-boranes and general stability rules are briefly reviewed. Oxidation of the 7,8-C2B9H2 anion was found to afford selectively various new nido-carboranes, namely, 5,6-C2B8H,2, n-C4B,8H22, iso-C4B18H22 and the C4B15H3 anion. The 5,6-C2B8H,2 was used as the starting material in syntheses of further new or known compounds, e.g. 1,2-C2B8H,0, 1,10C2B8H,O, 6,9-C2B8H,4, 5-Cl-6,9-C2B3H,3, l,3-C2B7H13 etc. Analogous oxidations of substituted (Br, C6H5) C2B9H ions and the direct bromination and deuteration of the parent carborane in bridge-positions resulted in derivatives which made it possible to elucidate the ''B n.m.r. spectrum of 5,6-C2B8FI,2. The n-C4B,8H22 is a new carborane type, consisting of two C2B9H1, units, bonded by two three-centre exo-bonds. The structure was solved by combination of selected reactions [BH3-insertion, splitting with Lewis bases, reduction of the C4B, 8H salt] and elucidation of structures of the compounds formed. The accompanying iso-C4B, 5H22 is, according to its n.m.r. spectra, composed of the 5,6-C2B8H11 and o-carborane fragments attached by means of a B—B bond probably in position 8 of the former compound and 3 of the latter framework. The C4B,8H anion was revealed as a C2B9H, ,H-C2B9H,, system with a hydrogen bridge bound to B[9] of each unit. The reaction of the 7,8-C2B9H 12 anion with nitrous acid results in degradative insertion with the formation of novel l0-N-7,8-C2B8H,, and 8,9-NH 2-5,6C2B8H,, nido species. Under forced conditions, the p-carborane was degraded to a new 2,9C2B9H '2 anion, the acidification of which led to the relatively stable 2,9C2B9H,3 nido-carborane. On the basis of an intercomparison of various nido-carboranes with other members of this family and with nido-boranes, general stability rules for nidocarboranes are proposed. INTRODUCTION While the nido-boranes represent the oldest class, the analogous nidocarboranes are relatively the youngest and least investigated group of the borane family'. This article deals with the intermediate dicarba-nidoboranes of the C2B7 to C2B9 series. As the first representative of this dicarba-nido-borane group, 7,8-dicarbanido-undecaborane(13) was discovered by Wiesboeck and Hawthorne2. 431 J. PLEEK AND S. HEkMANEK This compound was obtained by alkaline degradation of 1,2-dicarba-closododecaborane(12) followed by acidification of the fairly stable nido-anion 7,8-C2 B9H 12• H OBH •CH Figure 1. Formation of 7,8-C2B9H13 from o-carborane2 Another important compound of this series, the nido-carborane 1,3C2B7H13 was observed by Hawthorne et al.3 as the main product in the oxidation of the 7,9-C2B9H ion. Figure 2. Oxidation of the 7,9-C2B9H anion to 1,3-C2B7H13 The 1,3-C2B7H13 carborane was used as the starting material in the synthesis of a further member, the 5,7-C2B8H12 carborane4.