Kinetic resolution of terminal epoxides with phenols promoted by heterometallic Co–Al and Co–Ga salen complexes

The binuclear chiral (salen) Co complexes bearing Lewis acid salt (Al and Ga) and 4-nitrobenzene sulfonic acid (NBS) catalyze the enantioselective ring opening of terminal epoxides with phenol derivatives. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of terminal epoxides with phenol and consequently provide enantiomerically enriched corresponding α-aryloxy alcohols (up to >99% ee). The two unit of salen complexes combined by Lewis acid exhibited co-operative catalysis during the ring opening reaction.     

Electropolymerization of chlorinated phenols on a Pt electrode in alkaline solution Part III: A Fourier transformed infrared spectroscopy study

FTIR spectroscopy was employed to investigate high molecular weight substances formed on a platinum electrode surface during the electrochemical oxidation of phenol and its chlorinated derivatives. Potentiodynamic (potential range from –0.80 V to 0.85 V vs SHE; scan rate 200 mV s^–1) and potentiostatic (at 0.78 V vs SHE) electropolymerization was used in alkaline solutions (1 M NaOH) containing 0.1 M of phenol, monochlorophenols, dichlorophenols, trichlorophenols and pentachlorophenol. The IR spectra of the corresponding monomers were recorded for the comparison. The FTIR spectroscopy studies revealed that the polymers formed under potentiodynamic and potentiostatic conditions are of aromatic nature (–C=C– stretching vibrations at 1450–1600 cm^–1), they have ether-linkages (=C—O—C= stretching vibrations at 1100–1300 cm^–1) and quinone groups (–C=O stretching vibrations at 1630–1800 cm^–1 and –C—H out-of-plane bending at 760 cm^–1). The intensities of the hydroxyl group bands in most of the polymers are rather weak compared to those in the corresponding monomers. Vibrations at 2850–2960 cm^–1, which are present in most of the IR spectra of polymers formed under cyclic voltammetry conditions, correspond to the stretching vibrations of the sp³ hybridized C—H bond and suggest that the cleavage of the benzene ring occurs to some extent during electrooxidation–electropolymerization of phenol and its chlorinated derivatives when reaching the potential of oxygen evolution (0.85 V vs SHE).     

An investigation of the polymerization of pyridine with epoxy compounds

The chemical reaction between pyridine and epoxy compounds has been investigated. This reaction disrupts the aromatic nature of the heterocyclic ring of pyridine, resulting in the formation of a polymeric material that contains cyclic amide structures. The polymer formed is not due to the homopolymerization of the epoxy groups. Based on the spectral studies, a reaction scheme is proposed. The order of reactivity for different pyridine derivatives has been obtained.     

Bifunctional initiators: synthesis of phenylazo-formamidoethyl 4-t-butylazo-4-cyanovalerate

Summary The paper deals with the synthesis of the phenylazo-formamidoethyl 4-t-butylazo-4-cyanovalerate, a product which — by its two azo groups having different thermal stabilities — may be used in initiating processes of stepwise radicalic polymerization. The preparation is based on the condensation of the 4-t-butylazo-4-cyanovaleric acid chloride with N-hydroxy ethyl-phenylazoformamide (HEPF) in anhydrous chloroform, in the presence of pyridine. The initiator purification involves its passing over an alumina column, on using methylene chloride as eluent. HEPF is a new intermediate obtained by the reaction of the ethyl phenylazocarboxylate with ethanolamine. Both the HEPF structure and that of the bis-azo initiator is confirmed by elemental analysis and spectroscopic measurements (IR and H-NMR spectra), as well.     

Functionalization of dextran: Incorporation of carboxy groups by O-succinoylation

The modification reaction of dextran with succinic anhydride using pyridine as catalyst and N,N-dimethylformamide/lithiumchloride system as solvent was studied. The structure of the resulting polymers was determined by means of ¹H and ¹³C NMR spectroscopy. A linear dependence of the reaction rate on succinic anhydride concentration was found. The orders with respect to pyridine and polymer concentrations were 1 and 2, respectively. The activation energy was found to be 69.0 kJ/mol. ¹³C NMR spectra at 75.4 MHz of partially modified dextran with monosuccinate groups were studied in order to evaluate the selectivity of the reaction of dextran with succinic anhydride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of individual hydroxy groups decreases in the order C-2 ∽ C-3 > C-4. For samples with higher degree of substitution the order is C-4 > C-3 > C-2. The results were explained by considering the formation of intramolecular hydrogen bonds as well as by steric considerations.     

Preparation and characterization of Pt/HMFI–SBA-15 hybrid catalyst for tetralin transformation

A Pt catalyst supported on a hybrid material, HMFI–SBA-15, was prepared. Both, support and catalyst (Pt/HMFI–SBA-15) were characterized by nitrogen physisorption, small and wide (2θ) angle XRD patterns, FT-IR, SEM and HRTEM. The acidic properties of the hybrid material were studied by cumene dealkylation and those of the catalyst were studied by FT-IR of adsorbed pyridine. The catalyst, Pt/HMFI–SBA-15, was tested for tetralin transformation at various reaction temperatures 498, 523, 548, 573, 585 and 598 K. Wide-angle XRD and FT-IR in the skeletal region indicate the presence of MFI zeolite fragments incorporated onto SBA-15. The characterization of the acid sites on the support by cumene dealkylation and FT-IR pyridine adsorption revealed the presence of Brönsted acid sites related to the HMFI zeolite fragments in the hybrid materials. For the catalyst, a homogeneous distribution of Pt clusters was found by HRTEM. In the transformation of tetralin, at all the reaction temperatures, the main products were trans + cis-decalins. However, at high reaction temperature ring contraction to spirodecane and dehydrogenation to naphthalene were observed. At 598 K, a maximum of 8% of ring contraction products was obtained.     

The anomalous behaviour of isoquinoline relative to quinoline and its significance in relation to structure and reactivity

Vapour phase catalytic oxidation of quinoline over a vanadia base catalyst yielded nicotinic acid, while vapour phase catalytic ammoxidation gave 3-cyano-pyridine, the benzenoid ring undergoing cleavage in both cases. The isomeric molecule, isoquinoline, was however found to behave in sharp contrast, undergoing an unexpected reaction in its transformation into phthalimide during identical conditions of oxidation and into ortho-phthalonitrile during ammoxidation, the pyridine ring undergoing cleavage in both cases, with the appearance of the heterocyclic ring nitrogen in a reactive functional group. The significance of these observations is discussed in relation to structure and reactivity and possible reaction mechanisms are suggested.     

Synthesis,characterization and controlled release behaviour of adducts from chloroacetylated cellulose and α-naphthylacetic acid

Celluloses partially functionalized with chloroacetate groups were obtained by reaction of cellulose with chloroacetyl chloride using pyridine as catalyst and the dimethylacetamide/LiCl system as solvent. ¹³C NMR spectra at 75.4 MHz of partially modified cellulose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of cellulose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6>C-3>C-2. The coupling of α-naphthylacetic acid to cellulose functionalized with chloroacetate groups was carried out by reaction with their potassium salts or directly in the presence of 1.8-diazabicyclo[5.4.0]-7-undecene. High degrees of modification were obtained by both methods. However, the esterification reaction is somewhat more efficient in the case of the potassium salt. The kinetic results were consistent with a second-order reaction. The hydrolysis in the heterogeneous phase of cellulose–α-naphthylacetic acid adducts showed that the release of the bioactive compound is dependent on the hydrophilic character of the adduct as well as on the pH value of the medium.     

Metal ion functional polybenzoxazine based on phenol and 2-aminopyridine

A novel Co²⁺ ion functional benzoxazine monomer based on phenol and 2-aminopyridine was prepared, polymerized by step-wise curing and characterized via direct pyrolysis mass spectrometry in addition to classical spectrometry techniques. Curing of neat monomer yielded a highly cross-linked polymer as a consequence of competing and consecutive reactions involving the heterocyclic ring opening followed by attack of –NCH₂ groups to ortho and para positions of phenol and pyridine rings and coupling of –NCH₂ groups. On the other hand, the coordination of metal ion to nitrogen atoms of the pyridyl rings inhibited the attack of –NCH₂ groups to ortho and para positions of pyridine rings and eventually decreased the extent of cross-linking.     

Copolymerization of methylacrylate with electron-donor N-(2-hydroxyethyl) carbazolyl acrylate and n-butylacrylate with electron-acceptor (β-hydroxyethyl)-3,5-dinitrobenzoyl acrylate

Summary The radicalic copolymerization at 60° C, initiated by AIBN, in the mixture of the none chain transfer solvent benzene and the chain transfer solvent dioxane of methylacrylate with the electron-donor N-(2-hydroxyethyl)carbazolyl acrylate obeys the terminal model. The copolymerization in the same conditions of n-butylacrylate with the electron-acceptor (-hydroxyethyl)-3,5-dinitrobenzoyl acrylate failed and the desired copolymers were synthesized by radical copolymerization of n-butylacrylate with acryloylchlorid at 85° C in benzene, followed by the polymer analogue reaction with -hydroxyethyl-3,5-dinitrobenzoate in benzene/THF and with pyridine as base. The reactivity ratios of the binary system, computed in accordance with the Kelen-Tüdös method were used for constructing the copolymerization diagramm, to calculate the sequence distribution and to proof the glass transition — sequence distribution correlations.Herrn Professor Rüchardt zum 60. Geburtstag herzlich gewidmet     

Functionalization of amylose with chloroacetate groups and their derivation with α-naphthylacetic acid. Heterogeneous hydrolytic behaviour of the resulting adducts

Amylose functionalized with chloroacetate groups was obtained by reaction of amylose with chloroacetyl chloride using pyridine as catalyst and the dimethylformamide/LiCl system as solvent. ¹³C-NMR spectra at 75.4 MHz of partially modified amylose with chloroacetate groups were studied in order to evaluate the selectivity of the reaction of amylose with chloroacetyl chloride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C-6 > C-3 > C-2. The coupling of a model bioactive carboxylic acid (a-naphthylacetic acid) to amylose functionalized with chloroacetate groups was carried out by reaction with its potassium salt. High degrees of modification were obtained in all cases. The hydrolysis in the heterogeneous phase of amylose-a-naphthylacetic adducts showed that the release of the bioactive compound is dependent on the sample form and the hydrophilic character of the adduct as well as on the pH value of the medium.     

On the mechanism of the electrochemical reduction of the La(III)—alizarin complexone complex with and without F in (CH2)6N4---HNO3

The mechanism of the electrochemical reduction of the La(III)—alizarin complexone(L) complex with and without F⁻ at the mercury electrode was investigated in (CH₂₆N₄---HNO₃(pH4.3). The reaction scheme can be written as follows: For La(III)—alizarin complexone system, in the solution: at the electrode:

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For La(III)—alizarin complexone—F⁻ system, in the solution: at the electrode:

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where L′ and L″ are the products of the reduction of L in these complexes adsorbed on the surface of the electrode.     

Reaction of 3-methyl phenol with tung oil

The aromatic ring substitution reaction of 3-methyl phenol with tung oil under acidic conditions was carried out. The product was analyzed to find out if 3-methyl phenol was subjected to the ring substitution reaction with tung oil at its conjugated double bonds. Up to two molecules of 3-methyl phenol were addition-reacted with the conjugated triene of one eleostearyl group of triglyceride of α-eleostearic acid which is the major component of tung oil. The 4-position of 3-methyl phenol was preferentially subjected to the cresol's ring substitution. Therefore, up to 6 mol of 3-methyl phenol was added to 1 mol of tung oil, most of which was bonded to 3-methyl phenol at its 4-position. When 3-methyl phenol was reacted with a relatively large amount of tung oil, the substitution reaction occurred at the 6-as well as 4-position of 3-methyl phenol to yield a tung oil dimer having 3-methyl phenol units in its molecule. The above results were confirmed by infrared (IR), nuclear magnetic resonance (NMR), and high-speed liquid chromatographic (HLC) analyses.     

HYDROGENOLYSIS OF DIPHENYL ETHER

Hydrogenolysis of diphenyl ether was investigated at 550°C and 620°C and at pressures up to 1850 psig. Primary interest was the elucidation of cracking patterns at a hydrogen to diphenyl ether molar ratio of 2:1.

The primary reaction was C—O—C bond cleavage resulting in the formation of benzene and phenol. The secondary reaction was ring cracking resulting in the formation of gaseous components namely, carbon monoxide, carbon dioxide and lighter hydrocarbons.     

Improved Turnover Numbers in Palladium‐Catalyzed Bisdiene Cyclization‐Trapping using N‐Heterocyclic Carbene Ligands

An optimized palladium‐N‐heterocyclic carbene catalyst system effects the palladium‐catalyzed bisdiene cyclization‐trapping with phenol at the 0.01% catalyst loading level with a TON of 7.6×10³ and TOF of 280 h⁻¹, values much higher than typically found for this and related carbocyclizations. The reaction scales well and the trans‐substituted six‐membered ring product is obtained in excellent yield on a 10‐mmole scale without further optimization of the catalyst system or reaction conditions.     

Gemeinsame kondensation von phenol,melamin und formaldehyd. III. Vorkondensation

The condensation reaction between phenol, melamine, and formaldehyde at different conditions (pH-value, molar ratio of phenol and melamine) was investigated. Gel permeation chromatography, ¹³C NMR-spectroscopy and thermogravimetry showed the reactivity of phenol in the reaction with formaldehyde to be rather small at low pH values. At alkaline conditions this reactivity rises very fast. Melamine shows an inverse behaviour. Therefore neither at acidic nor at alkaline conditions cocondensates between melamine and phenol with formaldehyde are formed. Condensation, which involves both melamine and phenol, can be performed at pH-values between 6 and 9. In this range, the reaction can be controlled via acetone dilutability and turbidimetric titration.     

Quantitative 13C n.m.r. characterization of aqueous formaldehyde resins: 1. Phenol-formaldehyde resins

Phenol-formaldehyde (PF) resins which had experienced a variety of reaction conditions and/or ageing conditions were quantitatively characterized by ¹³C n.m.r. Under the specific conditions of this study, the phenol para position was favoured for reaction over the ortho position on a per site basis, particularly for condensation reactions. Increasing the reaction temperature from 23°C (14 days reaction) to 80°C (3 h reaction) did not alter the type of resin structure. Ageing PF resins resulted in extensive condensation and a drastic reduction in para-substituted methylol and hemiformal groups. This apparently contributes to a sharp reduction in the reactivity of these resins for reactions requiring methylol substituents on the ring.     

Molecular weight distributions in novolac type phenol-formaldehyde polymerizations

In the acid-catalysed condensation polymerization of phenol and formaldehyde, the ortho and para positions of the phenol ring are known to exhibit different reactivities^1,2. Along with this on polymer molecules, the internal sites have lower reactivity due to molecular shielding. To model the novolac formation, five reactive sites have been proposed³ and their reactivities are assumed to be completely determined by the site involved. To find the molecular weight distribution (MWD) of the polymer from this information, a given polymer chain has been assumed to consist of these sites in the same relative ratio as in the reaction mass. A mass balance, on polymer molecules of given size, has been made and solved numerically as a function of time. The sensitivity analysis has been carried out to show that the MWD is little affected by the variation of reactivities of the internal sites. The reactivity of para external positions and the ratio of phenol and formaldehyde, however, play a major role in determining the MWD.     

酚醛树脂用生物油反应活性的测试与分析

生物油的反应活性是制备生物油-PF(酚醛树脂)的关键因素。首先利用酚单体取代基共轭效益参数(Rc)评价了生物油中主要酚类物质的理论反应活性,然后测定了生物油/甲醛的实际反应能力,并与苯酚/甲醛的反应能力进行了对比,以此来评价生物油的整体反应活性。结果表明:生物油中酚类物质的理论反应活性为苯酚的29%;在10 g生物油中加入2.0 g NaOH,并且当反应温度为80℃和反应时间为90 min时,生物油的实际反应能力是苯酚的31%左右。     

Hydro-conversion of 1-methyl naphthalene into (alkyl)benzenes over alumina-coated USY zeolite-supported NiMoS catalysts

Hydro-conversion reactions were carried out at 360 °C under 5 MPa of H₂ pressure to study ring opening reactions of 1-methyl naphthalene using NiMoS supported on γ-alumina and alumina-coated/mixed USY zeolites. The catalysts were characterized using N₂ BET, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), pyridine FT-IR, and high-resolution transmission electron microscopy (HR-TEM) to study the influence of morphological and acidic properties on hydrogenation (HYD) and hydrocracking (HC) reactions. NMACZ-2 (NiMoS supported on the minimum amount of alumina-coated USY zeolite) showed enhanced reactivity for HC and produced (alkyl)benzenes with the highest yield, of ca. 80%. By-products were tetralin, decalin and cyclo-paraffin species. The tetralin species produced using NMACZ-2 moved into the alumina-coated USY zeolite support before undergoing HYD to produce decalin species, which were rapidly and selectively hydro-cracked into (alkyl)benzenes. A large amount of decalin was produced through the HYD of tetralin without significant cracking, possibly due to the weak acid character of γ-alumina. Bulk phase Mo oxide species on NMAZ (physical mixture of alumina and USY zeolite), as well as deactivation of the catalysts due to coke formation over the naked zeolite surface, inhibited the ring opening of tetralin, decreasing the yield of (alkyl)benzene. Various morphologies, such as the MoS₂ structure and acidic characteristics of the catalysts, were crucial factors affecting the HC reactivity of 1-methyl naphthalene.