An Inventory of Fluorspar Production, Industrial Use, and Emissions of Trifluoroacetic Acid (TFA) in the Period 1930 to 1999

There is a generally accepted conclusion that trifluoroacetic acid (TFA) does occur naturally, in part based on the large quantities of TFA in the oceans (61 - 205 million tonnes, measured in 1998-2002). However, the recent review paper “Insufficient evidence for the existence of natural trifluoroacetic acid” concludes that “the presence of TFA in the deep ocean and lack of closed TFA budget is not sufficient evidence that TFA occurs naturally, especially without a reasonable mechanism of formation”. Industrial sources of TFA can only result from the use of fluoride minerals in industrial processes. Major industrial uses of fluorspar started significant expansion from about the same time (1930s). Over 190 million tonnes of fluorspar have been mined in the period 1930 to 1999. An inventory has been developed (1930-1999), accounting for most of the fluorspar production (86%) and estimating emissions of TFA. Industrial emissions of TFA are estimated as 230,000 to 470,000 tonnes. Significant other industrial uses of fluorides have not been identified that could account for the large burden of TFA in the oceans. This inventory provides complementary evidence that the quantity of TFA in the oceans must include a large natural burden.

Actional Mechanism of Trifluoroacetic Acid for the Separation of Biopolymers by Reversed-phase Liquid Chromatography

The present paper covers the actional mechanism of trifluoroacetic acid for the separation of biopolymers investigated by using the parameters of stoichiometric displacement model for retention(SDM-R) in reversed-phase liquid chromatography. It was found that the trifluoroacetic acid(TFA) may participate in, or stimulate the association among displacing agent molecules in mobile phase, and decrease the affinity of both the associate molecules of the displacing agent and the TFA-protein ion-pairing. The former dominates over the separation selectivity of biopolymers as the concentration of TFA is lower than a given value, and the two contrary functions partly offset to each other and the latter dominates as its concentration is greater than the given value.

Temperature-controlled Cascade Reaction of Phloroglucinoltribenzyl Ether Promoted by Trifluoroacetic Anhydride and Trifluoroacetic Acid

We report the first trifluoroacetic anhydride- and trifluoroacetic acid-promoted cascade reaction with phtoroglucinoltribenzyl ether and carboxylic acid as starting materials. By simply varying the temperature of systems containing the same starting materials, different products were produced in high yields. A three-step consecutive reaction process was also proposed.

THE INTERACTION OF ETHYL BENZOATE AND TRIFLUOROACETIC ACID IN EXCITED STATE

This paper is concerned with the interaction of ethyl benzoate (EBA) and trifluoroaceticacid (TFA) molecules in the excited state by measurements of steady--state and transient fluo-rescence spectra at room and low temperatures. The results show that not only the 1:1 exci-plex but also the 2:1 triplex between EBA and TFA was formed. The formation pathway ofthe triplex is that the exciplex formed at first, then by the interaction with the EBA mole-cule it transformed into triplex. But it could not be formed by the dimer of EBA by interac-tion with TFA. The dimer of EBA is confirmed in the concentrated solution. So there arefour components in EBA/TFA--concentrated solution and their fluorescence lifetimes aremeasured respectively.

Coordinating Zirconium Nodes in Metal-Organic Framework with Trifluoroacetic Acid for Enhanced Lewis Acid Catalysis

Regulating Lewis acid sites with well-defined electronic state and steric environment is still challenging for achieving high catalytic efficiency.Here we show coordinating zirconium nodes in the typical metal-organic framework known as MOF-545 with the monocarboxylate modulators including trifluoroacetic acid(TFA)or benzoic acid(BA)over meso-tetra(4-carboxyphenyl)-porphine(H_(2)TCPP),denoted as MOF-545-TFA or MOF-545-BA.Impressively,MOF-545-TFA shows the significantly enhanced performance for the catalytic ring-opening reaction of various epoxides with alcohols and good recyclability at 40°C in respect with MOF-545-BA and ZrO_(2).This mainly originates from the stronger Lewis acidity and more active zirconium sites induced by the electron-withdrawing TFA,resulting in the increased ability for activation of epoxides.This modulation approach is promising for enlarging the toolbox to extend the MOFs-based Lewis acid catalysis.

The Effect of Trifluoroacetic Acid on Molecular Weight Determination of Polyesters:An in Situ NMR Investigation

Due to the poor solubility of aromatic polyesters in comm on orga nic solve nts,trifluoroacetic acid is usually used as a co-solve nt to increase their solubility for characterizations.However,only few studies have reported the side reactions induced by it.We present here the application of in situ 1H-NMR techniques to explore its effect on the hydroxyl end-groups,which are usually used for the molecular weight determination of polyesters by end-group estimation method.Using bis(2-hydroxyethyl)terephthalate(BHET)as model compound,quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent(1:10,V:V).This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid,revealed by the H-^(13)C gradient-enhanced heteronuclear multiple bond correlation(gHMBC)spectrum.The mixtures of dimethyl terephthalate and BHET with different molar ratios were used to represent poly(ethylene terephthalate)(PET)with different degrees of polymerization,and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied.Our results show that if a relative error of 5%is allowed,the NMR measurements must be finished within 1.3 h of solution preparation at 25℃ in the mixture solve nt.The results were confirmed in PET sample,while in poly(ethyle ne adipate),the obtained esterifaction con stant is faster that those in aromatic system.The results can be applied to other polymer systems with alcohol functionalized groups,and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

Communication A convenient trifluoroacetylation of amines with trifluoroacetic acid and titanium tetrachloride

In the past years,trifluoroacetylation has been widely used for protecting func-tional groups.For example,trifluoroacetyl can act as an effective blocking group ofhydroxyl and amino substituents in the reactions of a 1-halo-2-hydroxyl-3-amino sugarwith cholesterol or cyclodecanol.Furthermore,the conversion of the basic aminogroup to less basic amido group by trifluoroacetylation provides a good chromatographyseparation method of amines,e.g.cis-,trans-1,2-diaminocyclohexane can be separatedcompletely,via trifluoroacetylation by GLC technique.

Effect of Acidic Catalyst on Properties of Novel Conductive Copolymer Films Made of Pyrrole and Formyl Pyrrole

Effect of acidic catalysis having carboxylic acid group was studied on properties of conductive copolymer films made of pyrrole (Py) and 2-formyl pyrrole (FPy). It was noted that trifluoroacetic acid (TFA) and trichloroacetic acid (TCA) were suitable for the preparation of copolymer films, which showed good properties in its strength and electrical conductivity of the copolymer films. When the concentration of TFA or TCA was increased in the monomer feed, the copolymerization yield became higher and the obtained films showed electrical conductivity in the range of 10–4 - 10–3 S/cm. FT-IR and UV-Vis spectra confirmed the formation of conjugate chemical structure in the copolymer film.

Trifluoromethylation of Carbonyl Compounds with Sodium Trifluoroacetate

In the presence of copper （I） halide as catalyst, a variety of carbonyl compounds could be trifluoromethylated with sodium trifluoroacetate to give the corresponding alcohols in moderate to high yields.

Strongly enhanced flux pinning in the YBa_2Cu_3O_(7-X) films with the co-doping of Ba TiO_3 nanorod and Y_2O_3 nanoparticles at 65 K

YBa2Cu3O7-x（YBCO） films with co-doping BaTiO3（BTO） and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates（TFA-MOD）. The properties of the BTO/Y2O3co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction（XRD）, Raman spectra, and scanning electron microscope（SEM）. The optimized content of yttrium excess in the BTO/Y2O3co-doped YBCO films is 10 mol.%, and the critical current density is as high as - 17 mA/cm^2（self-field, 65 K） by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density（JC） not only at the self-magnetic field, but also in the applied magnetic field.

Synthesis，Characterization，Crystal Structure and Quantum Chemistry Calculation of the Mixed Ligand Complexes ［Ln（CF_3COO）_3·（Phen）_2·（H_2O）_2］·CH_3COCH_3·H_2O

The complexes of rare earth trifluoroacetate with two 1, 10-phenanthroline Ln (CF_3COO)_3 ·(Phen )_2· CH_3COCH_3·3H_2O (Ln=La, Pr, Nd, Sm, Eu) have prepared in the mixed slovents of H_2O and CH_3COCH_3, and the single crystal Nd (CF_3COO)_3· (Phen )_2· CH_3COCH_3· 3H_2O was determined by four-circle X-ray diffractometer. The crystal is a monoclinic system with space group P2_1/n(14# ), a=0. 9253 ( 1 )nm , b=2. 1500 ( 2 ) nm , c=1.8981 ( 4 ) nm, β= 95. 28( 1 )°, V=3.760(8) nm￣3 , Z=4 , R=0. 035. The coordination number of Nd is 9 , and the coordination polyhedron of Nd atom is distorted tricapped triagonal prism. The electronic structures and chemical bonds of the complex Nd (CF_3COO)_3· (Phen )_2· CH_3COCH_3·3H_2O is studied by the spin unrestricted INDO method.

Synthesis and Crystal Structure of Mn(phen)(CF_3COO)(H_2O)_3·NO_3

The mononuclear manganese complex Mn(phen)(CF3COO)(H2O)3NO3 (C14H14- O8N3F3Mn) has been synthesized, where phen = 1,10-phenanthroline. The molecular and crystal structures were determined by single-crystal X-ray diffraction. The crystal is of monoclinic, space group P21/c with a = 8.8550(3), b = 10.6529(3), c = 19.8763(2) ? ?= 97.762(2), V = 1857.78(8) 3, Z = 4, Mr = 464.22, Dc = 1.660 g/cm3, ?= 0.789 mm-1, F(000) = 940, T = 293(2) K, R = 0.0764 and wR = 0.2441 for 1995 observed reflections with I > 2s(I). In the crystal the manganese atom is six-coordinated by two chelated nitrogen atoms from phenanthroline, three oxygen atoms from water molecules and one oxygen atom from trifluoroacetate, completing an octahedral geometry.

Strong flux pinning enhancement in YBa_2Cu_3O_(7-x) films by embedded BaZrO_3 and BaTiO_3 nanoparticles

YBa2Cu3O7-x （YBCO） films with embedded BaZrO3 and BaTiO3 nanoparticles were fabricated by metalorganic deposition using trifluoroacetates （TFA-MOD）. Both X-ray diffraction and transmission electron microscopy revealed that these BaZrO3 and BaTiO3 nanoparticles had random orientations and were distributed stochastically in the YBCO matrix. The unique combined microstructure enhances the critical current density （Jc） of the BaZrO3/BaTiO3 doped-YBCO films, while keeping the critical transition temperature （Tc） close to that in the pure YBCO films. These results indicate that BaZrO3 and BaTiO3 nanoparticles provide strong flux pinning in YBCO films.

Iodomethane as an organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines

Iodomethane is usually used as an electrophilic methylation reagent.Herein,we report its use as a C1 organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines in the absence of a transition metal.Trifluoroacetic acid(TFA)was employed as an inexpensive,readily available trifluoromethyl source.The reaction efficiently produced a variety of trifluoromethylation products,with good functional group compatibility.Pyridine-containing drug molecules could also be selectively trifluoromethylated for late-stage functionalizations.Mechanistic studies showed that iodomethane selectively reacted with the pyridine starting material,rather than the pyridine product,to generate the corresponding N-methylpyridinium iodide.The decarboxylation of trifluoroacetic acid produced a trifluoromethyl anion,which added to the methylpyridinium iodide,and the subsequent aerobic rearomatization led to the generation of the ortho-trifluoromethylated product.

Synthesis and antidiabetic activity of β-acetamido ketones

This paper reports the use of trifluoroacetic acid as a catalyst in the Dakin–Westreaction for the synthesis of b-acetamido ketones. The method has several advantages such asrequiring only mild conditions and a low concentration of catalyst. Screening of 19 b-acetamidoketones for antidiabetic activity in vitro showed that their activity as peroxisome proliferatoractivated receptor (PPAR) agonists and as dipeptidyl peptidase 4 (DPP-IV) inhibitors wasfairly weak.

Synthesis of Novel Scolopendra-type Polydodecyloxybenzoyl[1,5]-diazocine as New Material for Optical Sensor

A new scolopendra-type polymer of polydodecyloxybenzoyl[1,5]-diazocine（PDBD） was designed and prepared using 2,5-bis（4-（dodecyloxy）-benzoyl）terephthaloyl azide with trifluoroacetic acid（TFA） via one-pot reaction in good yields. The structure of polymer was characterized using ~1 H-NMR, ^（13） C-NMR and MALDI-TOF spectra. The polymer PDBD exhibits good thermal stability as measured by TGA and DSC, and can be dissolved well in common organic solvents such as chloroform and tetrahydrofuran. In addition, UV-Vis spectral studies indicate that the polymer PDBD shows unique optical property changes（protonation/deprotonation） in the different trifluoroacetic acid environments. The new polymer is expected to be utilized as an optical functional material for fabricating optical sensors in environmental and biological fields.

Recent advances in the synthesis of fluoroalkylated compounds using fluoroalkyl anhydrides

Fluoroalkyl-containing organic compounds have exhibited wide applications in the field of pharmaceuticals,agrochemicals and materials science due to their outstanding properties such as biological activity,metabolic stability,lipophilicity,excellent chemical and thermal stability.Therefore,various synthetic strategies have been developed for the construction of fluoroalkyl-containing compounds,using highly active fluorinating reagents and fluorinated building blocks.Recently,the use of easily available and inexpensive trifluoroacetic anhydride(TFAA)and its anhydride analogues has attracted great attention to access numerous fluoroalkyl-containing compounds through cyclization and coupling reactions.In this review,we summarized the recent advances in the synthesis of fluoroalkylated compounds using fluoroalkyl anhydrides as reagents.This review aims to provide a reference for researchers on how to develop new synthetic straregies of fluorine-containing organic compounds and achieve kilograms or even tons preparation of fluorine-containing organic compounds using fluoroalkyl anhydrides.

Methyl 1,2-Shift Rearrangement on C-ring and Decarboxylation at C28 of Oleanolic Acid Derivatives

A new oleanolic acid derivative with A-ring lactone,C-ring rearrangement and decarboxylation at C28 was synthesized,which was confirmed by HRMS,NMR and X-ray crystal structure.It is the first report about the methyl rearrangement on C-ring of oleanolic phenylmethyl ester,and the possible mechanism was proposed as the 1,2-methyl shift.

Synthesis, crystal structure and photophysical properties of a neodymium trifluoroacetate complex with 2,2'-bipyridine

The neodymium trifluoroacetate complexes were synthesized and characterized by single-crystal X-ray diffraction for [Nd（CF3COO）3·Bpy·（H2O）3]Bpy（1）,elemental and TG analysis,FT-IR spectra,and PL spectra for Nd（CF3COO）3·Bpy（2）（Bpy：2,2＇-bipyri-dine）.The most interesting feature of the crystal structure for 1 is that it comprises a coordinated 2,2＇-bipyridine molecule and an out-sphere 2,2＇-bipyridine molecule.At the same time,the C-O distances appeared average which indicates the three atoms of carboxylato forming elec-tron-conjugate system.Hydrogen bond and π-π-stacking link the binuclear to two-dimensional sheet.The optical spectra for 2 exhibited that the complex possessed typical Nd（III） ion absorption and photoluminescence emission.The emission cross-section of 4F3/2→4I11/2 fluores-cence transition（3.63×10-20 cm2） was comparable with some laser glasses,which indicated good radiative properties of this neodymium trifluoroacetate complex in liquid matrix.The thermal analysis indicated that it was quite stable to heat.

Polymer assisted thick single-layer YBa_2Cu_3O_(7-δ)films prepared with modified TFA-MOD method

Single-layer YBa2Cu3O7-δ（YBCO） films with the thickness of over 600 nm were fabricated by modified metal organic deposition using trifluoroacetate metal organic deposition（TFA-MOD） method on LaAlO3（LAO） substrates. Polyvinylbutyral（PVB） was added into the precursor solution to enhance the thickness of the single layer. The pyrolysis process was shortened to about 3 h due to the reduction of the fluorine content in the precursor solution.The effects of heating rate during the crystallization process on the microstructure and Jcvalues of YBCO films were investigated. The α-axis-oriented YBCO crystals dominate when the heating rate is lower than 20 °C·min^-1, while faster heating rate of 43 °C·min^-1 results in pure c-axis epitaxial growth. The Jcvalues of YBCO films increase linearly with heating rate increasing due to the increase of c-axis YBCO growth, and the critical current（Ic） value of 100 A·cm^-1 within a single-layer YBCO film is achieved.