Reaction of wheat-straw structural components with a nitrating mixture containing trifluoroacetic acid

The reactions of wheat-straw (Triticum aestivum) cellulose, hemicellulose, and lignin with a mixture of nitric and trifluoroacetic acids and certain properties of the nitration products were studied for straw directly and for structural components isolated from it. The nitration products could be separated into nitrates of structural polysaccharides and nitrolignin by treatment with hot bases. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 477–479, September–October, 2006.     

Novel epimerization of aromatic C-nucleosides with electron-withdrawing substituents with trifluoroacetic acid-benzenesulfonic acid using mild conditions

Trifluoroacetic acid and benzenesulfonic acid in dichloromethane at ambient temperature have been found to be efficient co-catalysts for the epimerization of C-nucleosides with electron-withdrawing substituents. This approach provides a convenient route to the β anomer of the nucleosides with high yields in the range 54-78%. Synthesis of the 3′-phosphoramidite of 2,4-difluorophenyl C-nucleoside suitable for solid-phase DNA synthesis is described.     

Efficient epimerization of pyrene and other aromatic C-nucleosides with trifluoroacetic acid in dichloromethane

Trifluoroacetic acid has been found to be an efficient and non-oxidative catalyst for the epimerization of pyrene and other C-nucleosides in dichloromethane at ambient temperature. Aspects of the epimerization mechanism are also elucidated.     

萘甲腈和2,3-二甲基丁烯-2-光环加成反应:三氟醋酸的效应

在低转光解情况下,1-萘甲腈(1-NpCN)和2,3-二甲基丁烯-2(DMB)在环已烷或苯中的光环加成反应主要得到环丁烷3,但2-NpCN主要得到氨杂环丁烯6和少量的环丁烷5,三氟醋酸(TFA)量增加抑制1-NpCN和DMB的光环加成反应,表明TFA与基态及单激发态1-NpCN生成非光反应的复合物,它也淬灭^*(1-NpCN-DMB)激基复合物.在低浓度范围(0.1M以下)TFA加速2-NpCN和DMB光环加成反应,但在高浓度范围(大于0.1M)时又抑制反应.这些结果被解析如下:^*(2-NpCN-DMB)激基复合物和TFA反应增加5和6的得率,反之,是由于生成非光反应的基态复合物及淬灭单激发态2-NpCN.在非极性溶剂中二种单激发态萘甲腈生成TFA激基复合物的萤光与母体^*NpCN萤光区域几乎相同.     

Direct microwave promoted trifluoroacetylation of aromatic amines with trifluoroacetic acid

A simple microwave-promoted procedure has been developed for the direct preparation of trifluoroacetanilides. An equimolar mixture of substituted anilines and trifluoroacetic acid was microwave irradiated at short reaction times, giving the corresponding anilides in high yields and purity.     

Reaction of indoles with trifluoroacetic acid

3-Trifluoroacetyl indoles are formed by the action of trifluoroacetic acid on indole-2-carboxylic acid and its benzo-substituted derivatives. When unsubstituted indole is refluxed with trifluoroacetic acid, it gives 3-trifluoroacetylindole in 30% yield.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1235, September, 1981.     

Surface properties of aqueous solutions of trifluoroacetic and acetic acid mixture

The coadsorption of trifluoroacetic and acetic acid at the free surface of water was investigated. Knowing the composition of mixed monolayer and the effective dipole moments of individual molecules, the surface potential was calculated. The synergetic effect of the surface properties of mixed adsorbed films was observed.     

2-Cyanoacrylates in the conjugate addition of trifluoroacetic acid and nucleophilic reagents

In the presence of trifluoroacetic acid, ethyl 2-cyanoacrylate readily reacts with nucleophilic reagents, such as 2-chloro-1,3,2-benzodioxaphosphole, (EtO)₃P, (EtO)₂PCl, Ph₂PCl, Ph₃P, and thiourea. In these reactions the acid proton enters position 2 of the cyanoacrylate, whereas the nucleophilic component enters position 3, in accordance with the electron density distribution in the acrylate. In the absence of trifluoroacetic acid the above reagents, except 2-chloro-1,3,2-benzodioxaphosphole, cause ethyl 2-cyanoacrylate polymerization. The interaction of ethyl 2-cyanoacrylate with 2-chloro-1,3,2-benzodioxaphosphole and trifluoroacetic acid is the first example of a 2-cyanoacrylate taking part in the acid-initiated electrophilic conjugate addition of a weak nucleophile.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1245–1247, July, 1993.     

Sodium borohydride reduction of aromatic carboxylic acids via methyl esters

A number of important aromatic carboxylic acids precursors, or intermediates in the syntheses of natural products, are converted into methyl esters and reduced to the corresponding primary alcohols using a sodium borohydride-THF-methanol system. The alcohols are obtained in 70–92% yields in 2–5 hours, in a pure state. This two-step procedure not only provides a better alternative to aluminum hydride reduction of acids but also allows the selective reduction of esters in presence of acids, amides, nitriles or nitro functions which are not affected under these conditions.     

Regioselective thiocyanation of aromatic and heteroaromatic compounds using ammonium thiocyanate and oxone

An efficient and regioselective approach for the thiocyanation of indoles, pyrrole, aromatic amino compounds, and 2-methoxycarbazole has been developed using ammonium thiocyanate as a thiocyanation reagent and oxone as an oxidant.     

Reaction of trifluoroacetic anhydride with 4-pyridinecarboxylic acid hydrazide

Russian Journal of General Chemistry -     

The reaction of thiocaprylic acid with methyl thiocyanate

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2154–2155, September, 1989.     

Hydrogen bonding of organic bases with trifluoroacetic acid in chloroform: A method of calculating association constants of multi-equilibria systems

¹³ C NMR chemical shifts of sixteen organic bases, hydrogen-bonded with trifluoroacetic acid in deuteriochloroform, are used to calculate equilibrium constants for self-association of acid and for hydrogen bonding of base with various acid n-mers. In this treatment each hydrogen bond of the species in equilibrium is assigned a free energy. The equilibrium constants then correspond to changes in these energies. Thermodynamic models are proposed which differ in the extent to which a given hydrogen bond perturbs the free energies of neighboring bonds in the molecular aggregates. Each furnishes a minimum set of independent, freely variable equilibrium constants, the values of which are then determined through a least squares fitting of the experimental data by an iterative procedure.     

Separation of conjugated linoleic acid methyl esters by silver-ion high performance liquid chromatography in semi-preparative mode

Silver-ion HPLC (Ag-HPLC) has been utilized to separate a variety of unsaturated fatty acid methyl esters (FAMEs) by configuration, location or number of olefinic or acetylenic bonds. Two analytical Ag-HPLC columns connected in series and an isocratic solvent system of acetonitrile (ACN) in hexane were used to fractionate 10-15 mg samples of a mixture of two deuterium-labeled isomers of conjugated linoleic acid (Z9.E11- and Z9,Z11-octadecadienoic acid-17,17,18,18-d4). "Baseline" (> 95%) resolution of the two isomers, which decreased with increasing weights of sample injected, was maintained by careful adjustment of the percentage of ACN in the ACN/hexane solvent system. Chemical purities of the isolated FAME were > 96%.     

Determination of thiocyanate with aromatic halosulphonamides in acid and alkaline media

Ten organic aromatic halosulphonamides, both mono and dihalo compounds, ranging from chlorosulphonamides to iodosulphonamides, have been prepared and characterized by their infrared and NMR spectra and successfully used for determining thiocyanate in its metal salts and complexes. The proposed procedures are simple, rapid and reproducible, with an error of about +/-0.8%. These procedures are also useful for computing the number of thiocyanate ligands present in the complexes. Comparison of the present results with those from the argentometric method shows excellent agreement. The oxidation involves an 8-electron change per thiocyanate ion with the chloro and bromosulphonamides and a 6-electron change with iodosulphonamides.     

H3PW12O40／CeO2光催化脱色甲基橙溶液的研究

以CeO2为载体,用浸渍法制备了不同负载量的磷钨酸催化剂,并且考察了催化剂光催化脱色甲基橙溶液的催化性能。结果表明:磷钨酸最佳负载量为9%(质量分数);光催化剂加入量为300mg/100mL;在较低浓度下,甲基橙溶液的光催化脱色反应符合一级动力学方程;H3PW12O40/CeO2与TiO2具有相同的催化性能;催化剂再生后活性可恢复至65%。     

Chromatography of inorganic ions on polyethyleneimine cellulose layer in hydrochloric acid — Ammonium thiocyanate media

Summary Thin-layer chromatographic behavior of 58 inorganic ions on polyethyleneimine (PEI) cellulose has been systematically surveyed in hydrochloric acid — ammonium thiocyanate media. In this media most of the ions distribute chromatographically on the layer. Ag(I), Hg(II), Pd(II), Au(III), Bi(III), Ru(III), Pt(IV), Nb(V), Ta(V), Mo(VI), and W(VI) are strongly retained, while alkali earths(II), Mg(II), As(III), Ti(IV), and Te(VI) are not absorbed to any great extent in this system. An interesting correlation was found between the R_f values on PEI-cellulose in the thiocyanate media and the paramagnetic moment of the rare earths(III). An oddeven fluctuation against the atomic number is also found for the heavy rare earths(III). Chromatographic separation of many inorganic ions of analytical interest is demonstrated in this system.