Absorption and fluorescence of 2,5-diarylidenecyclopentanones in acidic media: evidence for excited-state proton transfer

Spectroscopic properties for a series of 2,5-diarylidenecyclopentanones in weak and strong acid environments are reported. Electronic absorption and fluorescence spectra have been measured for the all-E configurations of 2,5-dibenzylidenecyclopentanone (1), 2,5-bis(3-phenylallylidene)cyclopentanone (2), and 2,5-bis(5-phenylpenta-2,4-dienylidene)cyclopentanone (3) in acetic acid and sulfuric acid solutions. The spectroscopic evidence indicates that in 96% sulfuric acid 1, 2, and 3 are protonated both in the ground state and on the S1 potential energy surface. This assignment is supported by Zerner's intermediate neglect of differential overlap (ZINDO) and time-dependent density functional theory (TD-DFT) calculations. In glacial acetic acid, 1, 2, and 3 are unprotonated in the ground state. The absence of observable fluorescence from 1 in glacial acetic acid indicates that S1 is npi, whereas the observation of fluorescence from 2 and 3 in acetic acid is consistent with S1 being pipi. A combination of spectroscopic data, molecular orbital calculations, and fluorescence lifetime measurements indicate that 2 and 3 undergo intermolecular excited-state proton transfer in glacial acetic acid and diluted sulfuric acid solutions. Photochemical studies reveal that, unlike its behavior in organic solvents, 1 does not undergo efficient E,E --> E,Z photoisomerization in 96% sulfuric acid.     

Preparation of soluble and fusible poly(2,5-dimethoxy-1,4-phenylene)

Poly(2,5-dimethoxy-1,4-phenylene) was prepared by oxidative polymerization of p-dimethoxybenzene with aluminum chloride and copper(II) chloride in nitrobenzene under reduced pressure. The polymers obtained were soluble in sulfuric acid and fusible at 320°C. The intrinsic viscosity of the polymer was ca. 0.07 in sulfuric acid. Demethylation of methoxy groups did not occur during the polymerization.     

Partial ladder polymers with anthraquinone units. Reaction of 1,2,5,6-tetraaminoanthraquinone with p-benzoquinone derivatives

1,2,5,6-Tetraaminoanthraquinone has been condensed with 2,5-diaminobenzoquinone, 2,5-diaminobenzoquinone diimide, and 2,5-diaminohydroquinone to give partial ladder polymers which are only slightly soluble in sulfuric acid and do not produce soluble products on reduction with sodium dithionite in alkaline media.     

Determination of organic substances by standard chromous chloride solution

The reducibility of a number of organic compounds by a standard chromous chloride solution, prepared determinately from potassium dichromate, has been studied. Orange II, tartrazine, and azoxybenzene (after rearrangement in sulfuric acid medium to the corresponding azo compound) were quantitatively cleaved to the corresponding amines, while azobenzene was reduced only to hydrazobenzene (extent of reduction uncertain). Also quantitatively reduced were: propiolic acid to propenoic acid, diacetyl to acetoin, and benzil to benzoin. Hydrazobenzene, diphenylacetylene, 2-methyl-3-butyn-2-ol, 1-ethynyl-cyclohexanol-1, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5-diphenyl-3-hexyne-2,5-diol, and acetylacetone were not reduced even at elevated temperatures.     

Biomass Conversion Products as Steel Corrosion Inhibitors

By-products formed in the conversion of vegetable biomass (multicomponent tar) were studied in comparison with the target products of the process (5-hydroxymethylfurfural, 2,5-diformylfuran) as inhibitors of corrosion of low-carbon steel in sulfuric acid at temperatures of 25-90°C. The gravimetric method was used to determine the inhibiting effect of additives. All these additives exhibit medium protective effects in an acid medium, with the degree of protection in 1 M sulfuric acid at room temperature exceeding 80%. The potentiody-namic polarization method was used to determine the influence exerted by the additives on partial reactions of the corrosion process. It was shown that the tar and 2,5-diformylfuran behave as additives of the cathodic type, and 5-hydroxymethylfurfural, as that of a mixed type. Temperature-kinetic calculations were used to determine the mechanism of action of the inhibitors. The corrosion process occurs in the presence of additives predominantly under the kinetic control.

     

Rigid-ladder polymers: Polymers containing anthraquinone recurring units

In an attempt to synthesize some processable ladder or partial ladder polymers containing anthraquinone recurring units, leucoquinalizarin was treated with 3,3′-diaminobenzidine. This polymer, which was a black powdery material, was slightly soluble in concentrated sulfuric acid and dimethylsulfoxide. Also, 1,5-diamino-2,6-dimercaptoanthraquinone was condensed with 2,5-dichloro-p-benzoquinone in pyridine to give a black powdery polymer. This was only partially soluble in concentrated sulfuric acid, but could be solubilized in alkali by reduction with sodium dithionite.     

Electrochemical oxidation of 2-methyl-5-ethylpyridine

2,5-Pyridinedicarboxylic (isocinchomeronic) acid was obtained by electrochemical oxidation of 2-methyl-5-ethylpyridine on a lead anode in sulfuric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1362–1363, October, 1970.     

A microwave-assisted synthesis of triphenodioxazines [TPDOs]

A convenient and efficient method for the synthesis of triphenodioxazines [TPDOs] 1 by oxidative cyclisation of 2,5-bis-(arylamino)-3,6-dichlorocyclohexa-2,5-diene-1,4-diones 6 using potassium persulfate as the oxidising agent in 95?97% sulfuric acid triggered by microwave irradiation is described.     

Voltammetry of 2,5-diphenyloxazole in acetonitrile-fuming sulfuric acid mixtures

2,5-Diphenyloxazole is protonated by sulfuric acid in acetonitrile solvent. The existence of a simple acid base equilibrium is demonstrated by u.v.—visible spectroscopy. Polarographic and cyclic voltammetric data suggest that the protonated heteroaromatic is reduced in a diffusion-controlled step at potentials slightly less negative than the nonprotonated form.     

Quantitative Determination of Phthalides in Molecules of Vinyl Polymers and Their Role in Radical Polymerization

The applicability to vinyl polymers of the procedure for quantitative determination of phthalide groups in polymeric molecules from the color of their sulfuric acid solutions was examined. The correlation between the intensity of the color of sulfuric acid solutions of polymers (polymethyl methacrylate, polystyrene) and the content of phthalide fragments incorporated into the polymer molecule was studied systematically on a quantitative level.     

Fluorometric Determination of WR-148, 946[α-DI-n-Butylaminomethyl-2,6-bis(Trifluoromethylphenyl)-4-Pyridine Methanol Hydrochloride] in Biological Fluids

Abstract

A fluorometric procedure for WR-148,946 is reported based upon a fluorophore formed in 9 N sulfuric acid. A study of various acidic, neutral, and basic media is presented to establish sulfuric acid as the solvent system needed for maximum fluorescence intensity. A profile of various normal solutions of sulfuric acid showed that 9 N gave highest fluorescence readings. The fluorophore in 9 N sulfuric acid is postulated to be an “ene” formed from dehydration of the drug. Fluorescence is linear over the range 2–1000 ng/ml of sample with a quantum yield of 0.45. Application of the procedure to the analysis of WR-148, 946 in human plasma and urine gave an accuracy of 2.5–6.2%.     

Synthesis of abietinol and dehydroabietinol polyfluoropolyoxaalkylacylates

New polyfluorinated acylates of diterpene alcohols were prepared by reactions of sodium abietinolate and dihydroabietinolate with perfluoro(2-methyl-3-oxahexanoyl), perfluoro(2,5-dimethyl-3,6-dioxanonanoyl), and perfluoro(2,5,8-trimethyl-3,6,9-trioxaundecanoyl) fluorides, and also of abietinol and dehydroabietinol with heptadecafluorononanoic acid in the presence of catalytic amounts of concentrated sulfuric acid.     

Spirocyclohexadienones. 5. Synthesis of 2-R-7a-methyl-3-(spirocyclohexa-2,5-dien-4-one)perhydro-1-indolines

2-R-7a-Methyl-3-(spirocyclohexa-2,5-dien-4-one)perhydro-1-indolines were obtained by the reactions of 1-(4-ethoxyphenyl)-2-methylcyclohexanol with nitriles (RCN) in dichloromethane in the presence of concentrated sulfuric acid.     

Bromination of deactivated polycyclic aromatic nitro compounds

Bromination of 2,7-dinitro-9,10-phenanthrenequinone, 2,5-dinitro-9,10-phenanthrenequinone, and 2,4,7-trinitrofluorenone with bromine in concentrated sulfuric acid in the presence of acetic acid gave, respectively, 4-bromo-2,7-dinitro-9,10-phenanthrenequinone, 2-bromo-4,7-dinitro-9,10-phenanthrenequinone, and 5-bromo-2,4,7-trinitrofluorenone. No bromination occurred in the absence of nitric acid. The same brominated polynitro compounds can be obtained under analogous conditions directly from unsubstituted 9,10-phenanthrenequinone and fluorenone.     

Acid hydrolysis of amides obtained by Beckmann rearrangement of methyl ketones oximes of unsaturated γ-lactone,aromatic, and alicyclic series

Beckmann rearrangement was performed of oximes of substituted 3-acetyl-4-methyl-5,5-dimethyl(pentamethylene)-2-oxo-2,5-dihydrofuranes in the presence of boron trifluoride etherate. Aiming at establishing the spatial arrangement of the oximes the hydrolysis was carried out of acid amides obtained by Beckmann rearrangement of oximes of methyl ketones belonging to unsaturated γ-lactone series and also to aromatic and alicyclic series. The hydrolysis with 20% sulfuric acid led to the formation of the corresponding acid and amine, and the hydrolysis with acetic and hydrochloric acids resulted in retrobeckmann rearrangement giving the initial oximes.     

3. Acetate manufacturing,process and technology 3.1 Chemistry of cellulose acetylation

Nowadays Celluloseacetate is mainly produced with the acetic acid process. After an activation with acetic acid and sulfuric acid the acetylation of the cellulose starts by adding acetic anhydride. The temperature and the catalyst concentration play an important role for the reaction. Beneath acetylation also degradation of the cellulose chains occurs. In the first step of the process cellulosetriacetate is formed. In a second step, the hydrolysis, several acetyl groups are removed to achieve an average degree of substitution of 2,5. The water content in this step influences the acetyl distribution.     

Silica Sulfuric Acid: An Efficient and Versatile Acidic Catalyst for the Rapid and Ecofriendly Synthesis of 1,3,4‐Oxadiazoles at Ambient Temperature

A rapid and green synthesis of 2,5‐disubstituted 1,3,4‐oxadiazoles is reported. The title compounds were prepared by the reaction of different acyl hydrazides and orthoesters in the presence of silica sulfuric acid under solvent‐free conditions. In this new process, reactions were run at ambient temperature and completed in a short period of time with high yields.     

Determination of tin in titanium alloys

Tin-titanium alloys are becoming increasingly important; consequently a good method is needed for the determination of tin in this type of material. In this paper an accurate iodometric procedure is proposed for the determination. The sample is dissolved in sulfuric acid and the titanium oxidized with potassium permanganate. Tartaric acid is added and the tin precipitated with hydrogen, sulfide. The sulfide precipitate is dissolved in a mixture of sulfuric, perchloric and nitric acids and the solution evaporated to fumes of sulfuric acid. Water and hydrochloric acid are added, and the tin is reduced with lead and antimony trichloride and titrated with iodine. A study was made of the interfering elements that might be found in titanium alloys. The effect of antimony trichloride in reducing interference from copper was investigated. The method is recommended for titanium alloys containing 0.05 to 5.0 per cent. tin.     

An expeditious and one-pot synthesis of unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles under microwave irradiation and solvent-free conditions

A one-pot synthesis of some unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles via cyclocondensation of benzoylhydrazines with orthoesters under solvent-free and microwave conditions are described here. The reaction is efficiently catalyzed by silica- supported sulfuric acid as it provided the title compounds in high yields and relatively short times. The catalyst is reusable and can be applied several times without considerable decrease in the yields and rates of the reactions.     

The Synthesis of Octahydro-7-phenylpyrazino[2,1-b][3]benzazepines

Octahydro-7-phenylpyrazino[2,1-b][3]benzazepine ( 1a ) was prepared from 1-methyl-3-phenylmethylpiperazine 5a by reaction with styrene oxide followed by sulfuric acid cyclization of the resulting alcohol 6a . The diastereomeric mixture 1a was further separated into the diastereomers 1a′ and 1a″ . Similarly 1-methyl-3-(3-chloro-4-methoxyphenyl)piperazine was reacted with styrene oxide to yield 6c which on cyclization with 1.5 equivalents of sulfuric acid in trifluoroacetic acid gave a 3:7 mixture of phenolic, 1d , and methoxy, 1c , octa-hydropyrazino[2,1-b][3]benzazepines. The reaction of the 2,5-piperazinedione 4c with sodium acetoxyborohydride gave a 49% yield of the 2-piperazinone 7 which was similarly carried on to the corresponding 1(2H)-oxohexahydropyrazino[2,1-b][3]benzazepine 9 .