Search results for "sulfuric acid"
showing 10 items of 83 documents
Comparison of Water Adsorption Properties of Cellulose and Cellulose Nanocrystals Studied by Near-Infrared Spectroscopy and Gravimetry
2017
The adsorption properties of water molecules on cellulose and cellulose nanocrystals (CNCs), isolated from defatted rice bran (DRB) by 55% sulfuric acid hydrolysis under sonication were investigated. The powdered samples of cellulose and CNCs were analysed by using near infrared spectroscopy (NIR) and gravimetry at 38% and 55% humidities. Small amounts of samples were dried under vacuum at 120°C and the NIR spectra of the dry samples and their spectra during the adsorption water molecules were measured by using an NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The quantitative adsorption of water molecules by the samples was determined by gravimetry. Second a…
ChemInform Abstract: Modified Photobehavior of Carboxylic Acid Derivatives Induced by Protonation.
1987
Abstract A series of carboxylic acid derivatives 1–6 containing a second interacting function have been converted into the corresponding O -protonated species or acylium ions upon treatment with 96% sulfuric acid or oleum, respectively, at room temperature. The resulting stable cations have been spectroscopically characterized and submitted to irradiation. Cis-trans photoisomerization was observed in the ionic speciesderived from trans -crotonic, fumaric and maleic acids, and maleic anhydride. By contrast protonated crotonolactone 5a+ was found to be photostable. Finally, protonated α-bromobutyrolactone 6a+ was clean and efficiently dehydrohalogenated to 5a+ upon irradiation. Since the norm…
Proton Acid-induced Rearrangements of α-Alkynylestradiol Methyl Ethers
1993
When subjected to proton catalysis, the α-alkynylestradiol methyl ethers 1a and 1b furnish the Rupe or Meyer-Schuster rearrangement products 2, 4, and 5a. In the presence of sulfuric acid, α-ethynylestradiol 3-methyl ether (1a) is converted into the D-homosteroid 3a. The use of deuterated acids gives rise to the formation of the corresponding deuterated steroids 2b, 2c, 3b, and 5b. Some mechanistic implications of these results are also discussed.
Synthesis of Symmetrical 1,4-Diarylphthalazines
1975
Abstract It is well known that 1, 4-diarylphthalazines are prepared by condensation of the appropriate ortho-diaroylbenzenes with hydrazine hydrate.1 As ortho-diaroylbenzenes can be obtained by oxidation of ortho-dibenzylbenzenes, a rapid method is proposed to obtain the ortho-dibenzylbenzenes (Ia) and (Ib) by reaction of the highly reactive2 veratrol with para-chloro- or ortho-chlorobenzyl alcohol in sulfuric acid. The products obtained gave by oxidation the ortho-diaroylbenzenes (IIa) and (IIb), which were transformed into the 1,4-diarylphthalazines (IVa) and (IVb) by treatment with hydrazine hydrate.
Determination of fluoride in rocks, soils, and fluoride-bearing minerals by separation using direct distillation in sulfuric acid medium and spectrop…
1989
Abstract An analytical method for fluoride determination in geological samples is proposed. It is based on a previous fluoride separation by distillation with a Teflon reactor. The variables that influence distillation quantitation (temperature, time, and acid concentration) are optimized. The influence of some species on fluoride recovery during distillation are studied, and conditions to avoid this influence are suggested. Fluoride determination is carried out by means of a spectrophotometric method [La(III)-F−-Alizarin complexone system] (N. T. Crosby, A. L. Dennis, and J. G. Stevens, Analyst (London), 1968, 93, 643–652). The method is applied to the analysis of soils, rocks, and fluorid…
ChemInform Abstract: Proton Acid-Induced Rearrangements of α-Alkynylestradiol Methyl Ethers.
2010
When subjected to proton catalysis, the α-alkynylestradiol methyl ethers 1a and 1b furnish the Rupe or Meyer-Schuster rearrangement products 2, 4, and 5a. In the presence of sulfuric acid, α-ethynylestradiol 3-methyl ether (1a) is converted into the D-homosteroid 3a. The use of deuterated acids gives rise to the formation of the corresponding deuterated steroids 2b, 2c, 3b, and 5b. Some mechanistic implications of these results are also discussed.
Leukocytoclastic vasculitis associated with sulfuric acid inhalation
2013
Penile burn due to sulfuric acid: A case report
2020
6-Amino-2-iminiumyl-4-oxo-1,2,3,4-tetrahydropyrimidin-5-aminium sulfate monohydrate
2019
The title compound, C4H9N5O2+·SO4 2−·H2O, is the monohydrate of the commercially available compound `C4H7N5O·H2SO4·xH2O'. It is obtained by reprecipitation of C4H7N5O·H2SO4·xH2O from dilute sodium hydroxide solution with dilute sulfuric acid. The crystal structure of anhydrous 2,4,5-triamino-1,6-dihydropyrimidin-6-one sulfate is known, although called by the authors 5-amminium-6-amino-isocytosinium sulfate [Bieri et al. (1993). Private communication (refcode HACDEU). CCDC, Cambridge, England]. In the structure, the sulfate group is deprotonated, whereas one of the amino groups is protonated (R 2C—NH3 +) and one is rearranged to a protonated imine group (R 2C=NH2 +). This arrangement is very…
The Coastal Sulfuric Acid Cave System of Santa Cesarea Terme (Southern Italy)
2017
Santa Cesarea Terme in Salento is the only area in which hypogenic caves have been recognized in the Apulia region. In this spa area, the rising of sulfidic thermal waters that mix with both recent fresh infiltration waters and coastal salt water has formed four active sulfuric acid speleogenesis (SAS) caves. These caves are characterized by the typical set of sulfuric acid meso- and micromorphologies, and also by the presence of both gypsum and native sulfur. In all caves, biofilms are visible in the sulfidic thermal waters and on the cave walls.