Extraction and quantification of antioxidants from low-density polyethylene by microwave energy and liquid chromatography

In this paper a experimental design is applied to optimize the quantification of hindered phenol Irganox 1076, phosphite antioxidant Irgafos 168 and their oxidized product tri[2,4-di-tert-butylphenyl]phosphate from low-density polyethylene (LDPE). The developed analytical method consists of two steps: microwave-assisted extraction and reversed-phase liquid chromatography (LC) coupled with ultraviolet diode-array detector. A Plackett-Burman design was carried out in order to find the significant experimental parameters affecting the antioxidants extraction by microwave energy. These parameters were subsequently optimized by a central composite design. The performed method allows extracting the studied antioxidants at low temperature in a short time without degradation of phosphite antioxidant Irgafos 168.     

Alkylation of pyrocatechol in <Emphasis Type="Italic">tert</Emphasis>-butyl alcohol-sulfuric acid-benzene

Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tertbutylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes.     

Chemistry of O-Benzoquinones and Masked O-Benzoquinones IV. Synthesis of O-Spirodienonelactones from Unsymmetric Catechols

We describe the syntheses of 6, 8-di-tert-butyl-, 7, 9-di-tert-butyl., 6,7-di-n-propyl and 8, 9-di-n-propyl-O-spirodienonelactone from 3, 5-di-tert-butylcatechol and 3, 4-di-n-propylcatechol.     

Rhodium-catalyzed hydroformylation of olefins: Effect of [bis(2,4-di-tert-butyl) pentaerythritol] diphosphite (alkanox P-24) on the regioselectivity of the reaction

Rhodium (I) associated with [bis(2,4-di-tert-butyl) pentaerythritol] diphosphite (I) as a ligand represents an active catalyst system for highly regioselective hydroformylation of various alkenes. The commercially available bis(2,4-di-tert-butyl)pentaerythritol diphosphite (alkanox P-24) (I), which has been used so far as an antioxidant in the stabilization of polymers, was used as a diphosphite ligand for the selective hydroformylation reaction of olefins. Excellent selectivity towards linear aldehydes and excellent conversions were achieved in the hydroformylation of alkenes. The hydroformylation reaction was applied to various olefinic substrates including the internal alkenes.     

Determination of the concentration profile and homogeneity of antioxidants and degradation products in a cross-linked polyethylene type A (PEXa) pipe

A solvent extraction technique has been developed to determine the concentration profile of two antioxidants and five degradation products of antioxidants in cross-linked polyethylene (PEX) materials. Irganox^® 1076 and two degradation products in a PEX pipe type A (PEXa) were detected after extraction in chloroform. Fick's second law of diffusion was used to verify that 24 h of extraction at room temperature was sufficient to extract Irganox^® 1076 and the degradation products from PEX materials with a thickness of 5 μm. With the use of gas chromatography and mass spectrometry, the concentration profile was measured at four different places on a 100 m PEXa pipe. A two-way ANOVA analysis showed that the composition of Irganox^® 1076 was homogenous in the radial direction and heterogeneous in the longitudinal direction. Two degradation products of antioxidants were detected, 2,6-di-tert-butyl-p-benzoquinone and 2,4-di-tert-butyl phenol. The composition of 2,6-di-tert-butyl-p-benzoquinone was found to be homogeneous in the radial and longitudinal direction. 2,4-Di-tert-butyl phenol was homogeneous in the radial direction but heterogeneous in the longitudinal direction.     

Formation and properties of a catalyst based on sodium and potassium hydroxides in the reaction of 2,6-di-tert-butylphenol with methyl acrylate

The nature of the cation (K⁺ or Na⁺) in hydroxides affects the temperature plot of the equilibrium constant of the reaction of KOH and NaOH with 2,6-di-tert-butylphenol (ArOH) and the conversion of EII and (or) NaOH to potassium or sodium 2,6-di-tert-butyl phenoxides, which are catalysts for the alkylation of ArOH by methyl acrylate. The kinetic method for determination of the composition of the catalyst formed from NaOH and ArOH was proposed. The nature of the cation in phenoxides ArOK or ArONa is a factor determining the kinetics of the reaction of ArOH with methyl acrylate. Two different kinetic schemes were proposed to describe the transformation of ArOH in the presence of ArONa or ArOK.     

Kinetics of the formation and dissociation of complexes of cobalt(II) with <Emphasis Type="Italic">meso</Emphasis>-Phenylocta(methyl)porphyrin derivatives in organic solvents

The influence of the deformation of the tetrapyrrole aromatic macrocycle and the electronic effects of substituents on the kinetic parameters in the formation and dissociation reactions of cobalt complexes of porphyrins are discussed on the basis of a study of the kinetics of the formation and dissociation of cobalt complexes with meso-phenyl octa(methyl)porphyrin derivatives: 5,10,15-triphehyl octa(methyl) porphyrin; 5,15-bis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; 5,10,15-tris-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; and 5,10,15,20-tetrakis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin in acetic acid and pyridine.     

The reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide

Reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide in aprotic solvents leads to the generation of semiquinone (SQ^.H), alkylperoxy (ROO^.), and alkyloxy radicals. The reaction of SQ^.H and ROO^. produces 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone, 3,6-di-tert-butyl-1-oxacyclohepta-3,5-diene-2,7-dione, and 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinone. The radical generated from solvent attacks SQ^.H at position 4 with C−C bond formation. 4-Benzyl-2,5-di-tert-butyl-6-hydroxycyclohexa-2,5-diene-1-dione produced in this way is transformed into 4-benzyl-3,6-di-tert-butyl-1,2-benzoquinone under the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1999.     

A New Voltammetric Approach for the Determination of Biomimetic Catalyst Kinetic Constants Based on Substrate Consumption

In the present study, a new voltammetric method is introduced for the determination of kinetic parameters of artificial metalloenzymes (biomimetic complexes) mimicking the catecholase activity towards 3,5-di-tert-butylcatechol (3,5-DTBC) or 2,5-di-tert-butylhydroquinone, and representing a promising alternative to common spectrophotometric method. To demonstrate the effectiveness of the electrochemical approach, two binuclear copper(II) complexes bearing the same pentadentate ligand and different ionic ligands were selected. Apparent kinetic parameters, such as maximum velocity (V_max), Michaelis-Menten constant (K_m), and turnover number (k_cat), obtained by the described method employing differential-pulse voltammetry were in good agreement with the data evaluated from UV-Vis spectrophotometric measurements.     

Solid-phase oxidation of 2,4-Di-tert-butylphenol and 3,6-Di-tert-butylpyrocatechol in the presence of alkali and alkaline earth metal halides under elastic deformation

Solid-phase oxidation of 2,4-di-tert-butylphenol to give 2,2′,4,4′-tert-butyl-6,6′-bisphenol and of 3,6-di-tert-butylpyrocatechol to afford 3,6-di-tert-butyl-l,2-benzoquinone was performed in the presence of alkali and alkaline earth metals halides under conditions of modified extrusion. The formation of the corresponding metal 3,6-di-tert-butylsemiquinolates was registered by ESR method. The different behavior of chlorides, bromides, and iodides was observed and rationalized basing on the dissimilar complexing ability of halogens. The mechanism of activated oxidation was assumed. The study was carried out under financial support of the Russian Foundation for Basic Research (grant no. 96-03-33253a). Deceased.     

Halogenation of n-substituted p -quinone monoimines and p -quinone monooxime esters: VIII. Halogenation of N -aroyl(arylsulfonyl)-2,6-di- tert -butyl-1,4-benzoquinone monoimines and their reduced forms

Chlorination of N-aroyl(arylsulfonyl)-2,6-di-tert-butyl-1,4-benzoquinone imines gave Z and E isomers of 4-arylsulfonylimino-2,6-di-tert-butyl-5,6-dichlorocyclohex-2-en-1-ones and Z isomers of 4-aroyl-(arylsulfonyl)imino-2,6-di-tert-butyl-5,5,6-trichlorocyclohex-2-en-1-ones, in which the tert-butyl group on the sp ³-hybridized carbon atom occupies exclusively the axial position. The formation of Z/E-isomeric structures is related to configurational stability of the chlorination products. The chlorination of 4-aroylamino-2,6-di-tertbutylphenols was found to be accompanied by replacement of one tert-butyl group by chlorine atom with formation of 4-aroylimino-6-tert-butyl-2,3,5,6-tetrachlorocyclohex-2-en-1-ones. Original Russian Text ? A.P. Avdeenko, V.V. Pirozhenko, O.V. Shishkin, G.V. Palamarchuk, R.I. Zubatyuk, S.A. Konovalova, O.N. Ludchenko, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 818–824. For communication VII, see [1].     

Novel bulky pyrazolylphosphine ligands for the Suzuki coupling of aryl chlorides

Bulky 1-(3,5-di-tert-butyl)pyrazolyl-dicyclohexylphosphine and 1-(3,5-di-tert-butyl)pyrazolyl-di-tert-butylphosphine were prepared from the reactions of 3,5-di-tert-butylpyrazolide and corresponding chlorodialkylphosphines. They were successfully employed as ligands in the Suzuki coupling reactions of phenylboronic acid and various aryl bromides and chlorides.     

Steric effects on forming different by-products in the formylation reaction of 2,4-dialkylphenol (dialkyl = t-Bu/t-Bu, t-Bu/Me and Me/Me) proved by their structural and spectral characterizations

In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-products, namely 2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3). These three compounds are fully characterized and single-crystal structures of 1 and 3 are further elucidated.     

Heterocycles Based on Sterically Hindered Phenols and their Derivatives. (Review)

Published data on the synthesis of heterocyclic compounds (derivatives of dibenzofuran, phenoxazine, benzodioxolane, etc.) based on sterically hindered 6-substituted 2,4-di-tert-butylphenols, 6-hydroxy-2,4- and 6-hydroxy-2,5-di-tert-butylphenols, and their redox-conjugated ortho-benzoquinones are reviewed.     

Microwave-assisted extraction (MAE) combined with gas chromatography–mass spectrometry (GC–MS) for determination of volatile small molecules to evaluate compatibility of antimicrobial peptide PL-5 spray with packaging materials

A simple and efficient method involving microwave-assisted extraction (MAE) combined with GC–MS was established to determine 1,3-di-tert-butylbenzene (DBB), 2,4-di-tert-butylphenol (DBP), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (DBHBA) for evaluating the compatibility of antimicrobial peptide PL-5 spray with drug-packaging materials. In this study, the antimicrobial peptide PL-5 spray was purified using a Welchrom C18 column, and the high-density polyethylene spray bottle with liquid collection tube was first mixed with absolute ethanol, which would be subjected to MAE for further measurement by GC–MS. Various experimental parameters were systematically optimized, and good linearities were obtained within the range of 0.05–1.00 μg/mL for DBB and DBHBA and 0.50–10.00 μg/mL for DBP, with limits of detection (LODs) of 0.99 ng/mL (DBB), 16.34 ng/mL (DBP), and 1.64 ng/mL (DBHBA). Satisfactory recoveries that ranged from 96.0% to 107.2% were acquired, and the relative standard deviation was ≤ 4.7%. The results showed that the maximum daily usage of DBB, DBP, and DBHBA was 9.859, 163.445, and 16.399 ng, respectively, which was far below the corresponding permitted daily exposure values according to the safety assessment, indicating that the migration of analytes did not bring any potential safety risk. The compatibility between the drug and the packaging materials was favorable.     

Verbindungen des Germaniums und Zinns. 3. Sterisch überladene Alkylarylstannane durch Übertragung und Isomerisierung von 2,4,6-Tri-tert-butylphenylgruppen

Compounds of Germanium and Tin. 3. Sterically Congested Alkylarylstannanes by Transfer and Isomerization of 2,4,6-Tri-tert-butylphenyl Groups Reaction of SnBr₄ and SnI₄ with 2,4,6-tri-tert-butylphenyllithium (ArLi) by rearrangement of two Ar-groups gives the stannanes ArR₂SnBr ( 3 ) and ArR₂SnI ( 4 ), R = 2-methyl-2(3,5-di-tert-butylphenyl)propyl, which by a further transalkylation reaction with methyl lithium yield ArR₂SnCH₃ ( 5 ). However, treatment of 3 and 4 with tert-butyl lithium exclusively leads to ArR₂SnH ( 6 ) which surprisingly is also obtained by reaction of ArRSnCl₂ with tert-butyl lithium, presumably by an intermolecular R-group transfer. The structures of 5 and 6 were confirmed by X-ray crystallography.     

Synthesis and structure of 7<Emphasis Type="Italic">H</Emphasis>-12-Oxa-3,7-diazapleiadenes

The molecular structures of 9,11-di-tert-butyl-2,4-dimethyl-7H-12-oxa-3,7-diazapleiadene and 7-acetyl-9,11-di-tert-butyl-2,4,6-trimethyl-7H-12-oxa-3,7-diazapleiadene were determined by X-ray analysis.     

New Opportunities for Duff Reaction

Reaction of 2,4-di-tert-butylphenol with urotropin in conditions of Duff reaction takes an abnormal route and instead of the expected di-tert-butylsalicylaldehyde provides a mixture of N-substituted 3,5-di-tert-butyl-2-hydroxybenzylamines and redox conjugate benzoxazines containing mostly 6,8-di-tert-butyl-3-(3,5-di-tert-butyl-2-hydroxybenzyl)-2H-3,4-dihydrobenz[e][1,3]oxazine. A solvolysis of an individual benzoxazine in the system HO(CH₂)₂OH-H₂O-HCl affords di(3,5-di-tert-butyl-2-hydroxybenzyl)amine, and in AcOH 3,5-di-tert-butylsalicilaldehyde. A mechanism of Duff reaction was suggested involving the formation of a benzoxazine intermediate.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 718–721.Original Russian Text Copyright © 2005 by Belostotskaya, Komissarova, Prokof’eva, Kurkovskaya, Vol’eva.     

Efficient One-Pot Synthesis of the GABAB Positive Allosteric Modulator (R,S)-5,7-Di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one

The GABA_B positive allosteric modulator (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (1) was synthesized in one pot from the anhydrous lithium salt of 2,4-di-tert-butylphenol and methyl trifluoropyruvate mediated by a stoichiometric amount of anhydrous gallium(III) chloride in 64% overall yield. The enantiomers of 1 were separated by chiral-phase HPLC (Chiralpak AD®), and the absolute configuration was determined by X-ray crystallography.     

Synthesis of 2,2′-diamino-7-tert-butyl-9,9′-spirobifluorene starting from 4,4′-di-tert-butylbiphenyl

Abstract  

A novel spirobifluorene diamine monomer, 2,2′-diamino-7-tert-butyl-9,9′-spirobifluorene, was obtained starting from the readily available reagent 4,4′-di-tert-butylbiphenyl. The key step of the synthesis is the introduction of a nitro group into the 2-position of the spirobifluorene through the loss of tert-butyl at the 2-position.