An Efficient and Selective Oxidation of Sulfides and Thiols with Silica-Supported 1,1,3,3-Tetramethylguanidine/Br2 Complex

Silica-supported 1,1,3,3-tetramethylguanidine/Br₂ complex is an efficient reagent for the selective oxidation of aliphatic and aromatic sulfides to the corresponding sulfoxides and the oxidative coupling of thiols to disulfides in aqueous solution at room temperature in a short reaction time.     

Selective and efficient oxidation of sulfides and thiols with benzyltriphenylphosphonium peroxymonosulfate in aprotic solvent

Benzyltriphenylphosphonium peroxymonosulfate could be used for selective oxidation of aromatic and aliphatic sulfides and thiols to their corresponding sulfoxides and disulfides under nonaqueous and aprotic conditions without catalyst.     

An efficient solvent free catalytic oxidation of sulfides to sulfoxides with hydrogen peroxide catalyzed by a binaphthyl-bridged Schiff base titanium complex

A titanium binaphthyl-bridged Schiff base complex proved to be an efficient catalyst for the hydrogen peroxide oxidation of aromatic and aliphatic sulfides to the corresponding sulfoxides in satisfactory yields under solvent-free conditions.     

Rapid, one-pot synthesis of α,α-disubstituted primary amines by the addition of Grignard reagents to nitriles under microwave heating conditions

A series of α,α-disubstituted amines have been prepared in a simple and efficient one-pot procedure by the addition of Grignard reagents to a series of aliphatic, aromatic, and heteroaromatic nitriles. Key to this reported procedure is the unprecedented addition of the Grignard reagent to the nitrile under heating by microwave irradiation which both significantly improves reaction yields and reduces reaction times. In general, the Grignard addition reaction is complete within 5-10 min at 100 °C followed by rapid reduction with sodium borohydride to give the target amines.     

Sequential spectrophotometric determination of inorganic arsenic species by hydride generation from selective medium reactions and colour bleaching of permanganate

A simple spectrophotometric method is presented for the sequential determination of inorganic arsenic (As) species in one sample. It is based on the sequential arsine generation from As(III) and As(V) using selective medium reactions, collection of the arsine generated in an absorbing solution containing permanganate and ethanol at 5 °C and subsequent reduction of permanganate by arsine. The decrease in permanganate absorbance at 524.2 nm is monitored for As determination. The acetic acid/sodium acetate and HCl mediums were used for selective arsine generation from As(III) and remaining As(V) in one solution, respectively. The effect of interferences and their possible mechanisms were discussed. Interferences from transition metal ions were removed by using a Chelex 100 resin. Under optimized conditions, the established method is applicable to the determination of 3-30 μg of each arsenic species. Good recoveries (96-102%) of spiked artificial sea water, tap water and standard mixtures of As(III) and As(V) were also found. The method is simple, accurate, precise and environmental friendly.     

Studies in the anthrapyridone field

It is shown that hydrogen chloride catalyzes the replacement of halogen in the reaction of halogenoanthrapyridines with aromatic amines. Cupric acetate, in the presence of potassium acetate at 80–120° C, does not catalyze the replacement of halogen in these substances. The replacement of the arylamino residues in position 6 of a number of 2, 6-diarylaminoanthrapyridines by alkylamine residues under the action of aliphatic amines, was noted.For part V, see [8].     

Catalytic oxidation of thiols to disulfides using iodine and CeCl3·7H2O in graphite

A very simple procedure for the efficient oxidation of thiols to disulfides catalyzed by I₂/CeCl₃·7H₂O in graphite and ethyl acetate as the solvent, in an open system at room temperature is described. The reaction proceeds cleanly under mild conditions and was performed with aromatic, aliphatic, and heterocyclic thiols.     

Microwave-assisted nickel(II) acetylacetonate-catalyzed arylation of aldehydes with arylboronic acids

Applying sealed vessel microwave heating at 180 °C in toluene the arylation of aromatic and aliphatic aldehydes with arylboronic acids using 1-2 mol % of Ni(acac)₂ as a catalyst can be performed efficiently within 10-30 min providing the desired diarylmethanols or benzyl alcohols in good yields.     

Preparation of Disulfides by the Oxidation of Thiols Using Bromine

Medium length aliphatic disulfides are easily synthesized via the bromine-oxidation ofthiols in the absence of solvent. Bromine can also oxidize long aliphatic and aromatic thiols to disulfides in solution. All yields are quantitative.     

Subcritical water extraction of organic matter from sedimentary rocks

Subcritical water extraction of organic matter containing sedimentary rocks at 300 °C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300 °C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300 °C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300 °C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300 °C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable replacement for conventional solvent extraction of sedimentary rocks, but can also be used for any organic matter containing mineral matrix, including soils and recent sediments, and has the added benefit of tailored extraction for analytes of specific polarities.     

Iodometric determination of aryldialkylamine-N-oxides

A simple, rapid and selective titrimetric procedure for the determination of 0.1–20 mg of aryldialkylamine has been developed. The method is based on the reduction of the aryldialkylamine oxides with iodide in acidic medium. The rate of reaction is accelerated by heating the reactants just to boiling, and after cooling the reaction products, the liberated iodine is titrated with thiosulphate solution, with starch as indicator. The method can be applied successfully to the determination of aryldialkylamine oxides in the presence of aliphatic and aromatic amine oxides and amines.Dedicated to the memory of the late Dr. Darwish Amin     

Determination of sulfur compounds in hydrotreated transformer base oil by potentiometric titration.

A method was developed to analyze the distribution of sulfur compounds in model sulfur compounds by potentiometric titration, and applied to analyze hydrotreated transformer base oil. Model thioethers were oxidized to corresponding sulfoxides by tetrabutylammonium periodate and sodium metaperiodate, respectively, and the sulfoxides were titrated by perchloric acid titrant in acetic anhydride. The contents of aliphatic thioethers and total thioethers were then determined from that of sulfoxides in solution. The method was applied to determine the organic sulfur compounds in hydrotreated transformer base oil.     

A new synthesis of β,γ-unsaturated esters from three components, aldehydes, chloromethyl p-tolyl sulfoxide, and tert-butyl acetate, via magnesium carbenoid 1,2-CH and 1,2-CC insertion as the key reaction

Addition reaction of 1-chlorovinyl p-tolyl sulfoxides, which were derived from various aldehydes, with lithium enolate of tert-butyl acetate at −78 °C in THF gave adducts in high yields. Magnesium carbenoids were generated by treatment of these adducts with Grignard reagents via the sulfoxide-magnesium exchange reaction. When the adducts were derived from alkyl aldehydes or electron-deficient aromatic aldehydes, carbenoid 1,2-CH insertion reaction took place from the magnesium carbenoids to afford β,γ-unsaturated butyric esters having a substituent at the β-position. On the contrary, when the adducts were derived from electron-rich aromatic aldehydes, carbenoid 1,2-CC insertion reaction took place from the magnesium carbenoids to give β,γ-unsaturated butyric esters having the aromatic group at the γ-position. Highly stereospecific 1,2-CC insertion reactions were observed in the latter reactions. This procedure provides a good way for a synthesis of β,γ-unsaturated esters from aldehydes with two carbon-carbon bond-formations.     

Fast spectrophotometric determination of titanium in rocks with 3,4-dihydroxybenzoic acid

A fast Spectrophotometric method has been developed for titanium determination in geological matrices, based on the mixture of the sample solution with an exact volume of a single chromogenic solution containing acetate buffer, ascorbic acid and 3,4-dihydroxybenzoic acid DHB, which forms with titanium(IV) ions a yellow complex with absorption maximum at 380 nm. The following parameters were studied: complex stability, pH effect, amount of DHB, amount of acetate buffer, obedience to Beer's law, amount of ascorbic acid and iron masking. The results demonstrated that titanium can be determined in the pH range 4.0–5.0, with a molar absorptivity of 1.43 × 10⁴ 1·mol^–1 cm^–1 and a limit of detection of 2.3 ng/ml. The methodology that allows analysis of 30 samples per hour. Common anions and cations do not interfere, even when present in large amounts. Iron(III) interference can be easily eliminated by reduction to iron(II) using ascorbic acid. Analytical characteristics of the proposed procedure, such as calibration sensitivity, analytical sensitivity, limit of detection and coefficient of variation, were determined. The procedure was applied for titanium determination in various standard geological matrices, with results of satisfactory accuracy and precision (RSD<1%).     

Titanium Trichloride Reactions: Dehalogenation

We have recently established preparative procedures for titanium(III) reduction of sulfoxides to sulfides¹ and nitroarenes to amines.² In continuation of this program which is aimed at exploring the synthetic potential of titanium(III) ion, we have found that α-haloketones undergo facile dehalogenation upon treatment with titanium trichloride.     

Selective deoxygenation of sulfoxides with thexylchloroborane-methyl sulfide complex

Thexylchloroborane-methyl sulfide complex selectively deoxygenated both aromatic and aliphatic sulfoxides to the corresponding sulfides in high yield and purity at 0° C without affecting some other reducible structures.     

Rapid reduction of heteroaromatic nitro groups using catalytic transfer hydrogenation with microwave heating

A method for the rapid, safe reduction of heteroaromatic and aromatic nitro groups to amines is described using catalytic transfer hydrogenation under microwave heating conditions. Commonly available Pd/C or Pt/C catalyst is extremely effective with 1,4-cyclohexadiene as the hydrogen transfer source. In the case of substrates containing potentially labile aromatic halogens, Pt/C is effective and results in little or no dehalogenation. In general, the reactions are complete within 5 min at 120 °C.     

Biodegradation and hydrolysis rate of aliphatic aromatic polyester

The biodegradation and hydrolysis rates of an aliphatic aromatic copolyester were measured in manure, food, and yard compost environments and in phosphate buffer solution (pH = 8.0) and vermiculite at 58 °C. Mineralization, molecular weight reduction, and structural changes determined by DSC, FTIR, and ¹H NMR were used as indicators of the biodegradation and hydrolysis rates. Poly(butylene adipate-co-terephthalate), PBAT, film biodegraded at distinctive rates in manure, food, and yard compost environments having different microbial activities. The highest biodegradation rate was found in manure compost, which had the highest CO₂ emissions and lowest C/N ratio. The possible presence of extracellular enzymes in manure and food composts may facilitate the hydrolytic reaction since greater molecular weight reduction rates were observed in these composts. ¹H NMR and thermal analysis revealed that, while PBAT is a semi-crystalline copolyester with cocrystallization of BT and BA dimers, the soft aliphatic domain (BA) and the amorphous region are more susceptible to hydrolysis and biodegradation than the rigid aromatic domain (BT) and the crystalline region.     

A one-pot, efficient, and odorless synthesis of symmetrical disulfides using organic halides and thiourea in the presence of manganese dioxide and wet polyethylene glycol (PEG-200)

Primary, secondary, tertiary, allylic, and benzylic halides are converted efficiently into symmetric disulfides in high yields using thiourea as the sulfur atom source. The reactions are odorless and are performed at 30-35 °C in wet PEG-200 using MnO₂ as an oxidant.     

Schnellverfahren zur jodometrischen Bestimmung des Wasserstoffgehaltes organischer Verbindungen

Zusammenfassung Eine neue Methode zur jodometrischen Bestimmung des Wasserstoffgehaltes organischer Verbindungen wird beschrieben. Die Probe wird mit Schwefelpulver vermischt und bei 1200° C im Stickstoff strom über Quarzwolle oder einem Platin- Quarzwollekatalysator zersetzt. Aus den schwefelhaltigen Pyrolyseprodukten bildet sich Schwefelwasserstoff, der in einer Zinksulfat-Natriumacetatlösung absorbiert und jodometrisch titriert wird. Die optimalen Reaktionsbedingungen wurden eingehend untersucht und auch in theoretischer Hinsicht erklärt.

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Summary A new method for the iodometric determination of the hydrogen content of organic materials has been described. The sample is mixed with powdered sulfur and decomposed at 1200° C in a stream of nitrogen over quartz wool or a platinum-quartz wool catalyst. The sulfur-bearing pyrolysis products yield hydrogen sulfide that is then, absorbed in a zinc sulfate-sodium acetate solution and titrated iodometrically. The optimal reaction conditions were thoroughly studied and also explained from the theoretical standpoint.