A relation between RF values of unidimensional and circular paper chromatography

1. R_F values of 12 amino acids were determined in phenol-water and benzyl alcohol-acetic acid-water using unidimensional and circular techniques of paper chromatography. 2. It has been observed that the square of circular R_F values (considering frontal boundary of solute) equals the linear R_F values, and this relation is valid for the amino acids as well as the sugars studied. 3. The relation is found to be independent of the distance traversed by the solvent in the case of both amino acids and sugars. 4. A theoretical support has been given to the experimental observations.     

Chromatographic examination of metallic ions: Stability of antimony halide compounds

The R_F values of the halides and tartrate of antimony have been determined using differing butanol-halide acid-water solvents,, from the results obtained it has been concluded that the anion of the metal solution plays an important part in the R_F value of some metal ions. Possible extensions of the Chromatographic method are suggested.     

Influence of fluorination on the characterization of fluorotelomer-based acrylate polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The relative degree of fluorotelomer-based acrylate polymers (FTACPs) fluorination was demonstrated to influence the sample preparation protocol for matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry. A homologous series of FTACPs were synthesized from fluorotelomer and hydrocarbon acrylates of different chain lengths, which varied the ratio of perfluorinated to hydrogenated carbons (R_F/R_H). The solubility of FTACPs in tetrahydrofuran (THF) and chloroform was observed to decrease for highly fluorinated FTACPs (R_F/R_H > 0.5) promoting FTACP aggregation. No dependence on the degree of fluorination was observed for the solubility of FTACPs in the fluorinated solvents α,α,α-trifluorotoluene (TFT) or dichloropentafluoropropanes (HCFC-225). For FTACPs with a low degree of fluorination such as poly(8:2 FTAC-co-HDA) (R_F/R_H = 0.375), MALDI-ToF analysis was successful using a conventional sample preparation protocol with THF, and dithranol (Dith) matrix. Conversely, the poor solubility of the highly fluorinated poly(8:2 FTAC-co-BA) (R_F/R_H = 1.5) in THF resulted in mass discrimination. Several fluorinated sample preparation protocols were evaluated for poly(8:2 FTAC-co-BA) using TFT and HCFC-225, and decafluoroazobenzene (DFAB) or 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) matrices. The high volatility of HCFC-225 decreased FTACP pooling during solvent evaporation in comparison to the less volatile TFT, and improved the quantity of detectable signals. MALDI-ToF analysis of poly(8:2 FTAC-co-BA) in a 95:5 HCFC-225:methanol with DCTB being the best sample preparation protocol for highly fluorinated FTACPs in this study producing the highest number of observable signals. Employing a fluorinated sample preparation offers the capability of analyzing other highly fluorinated polymers that are not compatible with conventional sample preparations.     

New hydrofluorocarbon (HFC) solvents for antimony pentafluoride: Generation and characterization of 1-alkoxypentafluoroallyl cations

Certain hydrofluorocarbons (HFC) stable towards the strong Lewis acid, antimony pentafluoride, were found to function as a solvent for this aggressive reagent. CF₃CF₂CH₂F (HFC-236cb) was demonstrated to be an excellent solvent for SbF₅ and was used for the generation of stable polyfluorinated benzyl and allyl cations. Using this solvent 1-methoxypentafluoroallyl cation and R_FOCFCFCF₂⁺ (R_F = n-C₃F₇ and n-C₄F₉), were generated and characterized by NMR spectroscopy.     

Thin-Layer Chromatography of Some Monothio-β-Diketonate Complexes of Nickel,Zinc and Cobalt

Abstract

A silica gel adsorbent has been successfully used to separate three series of nickel, zinc and cobalt complexes of 1,1-difluoro-4-mercapto-4-(2′-thienyl)but-3-en-2-one, 1,1,1-trifluoro-4-mercapto-4-(2′-thienyl)but-3-en-2-one, 1,1,1-trifluoro-4-mercapto-2-(2′-naphthyl)but-3-en-2-one. For comparative purposes R_F data for the protonated ligands are also included. The ZnL₂ complexes gave R_F values in single and binary solvent systems which were similiar to the R_F values of the ligands; whereas, the NiL₂ and CoL₃ complexes gave R_F values which paralled each other in most solvents.     

New rare earth metal-rich indides RE14Ni3In3 (RE=Sc, Y, Gd-Tm, Lu)—synthesis and crystal chemistry

The rare earth-nickel-indides RE₁₄Ni₃In₃ (RE=Sc, Y, Gd-Tm, Lu) were synthesized from the elements by arc-melting and subsequent annealing. The compounds were investigated on the basis of X-ray powder and single crystal data: Lu₁₄Co₂In₃ type, P4₂/nmc, Z=4, a=888.1(1), c=2134.7(4), wR2=0.0653, 1381 F² values, 63 variables for Sc_13.89Ni_3.66In_2.45; a=961.2(1), c=2316.2(5), wR2=0.0633, 1741 F² values, 64 variables for Y_13.84Ni_3.19In_2.97; a=965.3(1), c=2330.5(5), wR2=0.0620, 1765 F² values, 63 variables for Gd₁₄Ni_3.29In_2.71; a=956.8(1), c=2298.4(5), wR2=0.0829, 1707 F² values, 64 variables for Tb_13.82Ni_3.36In_2.82; a=951.7(1), c=2289.0(5), wR2=0.0838, 1794 F² values, 64 variables for Dy_13.60Ni_3.34In_3.06; a=948.53(7), c=2270.6(1), wR2=0.1137, 1191 F² values, 64 variables for Ho_13.35Ni_3.17In_3.48; a=943.5(1), c=2269.1(5), wR2=0.0552, 1646 F² values, 64 variables for Er_13.53Ni_3.14In_3.33; a=938.42(7), c=2250.8(1), wR2=0.1051, 1611 F² values, 64 variables for Tm_13.47Ni_3.28In_3.25; a=937.3(1), c=2249.6(5), wR2=0.0692, 1604 F² values, 64 variables for Tm_13.80Ni_3.49In_2.71; and a=933.4(1), c=2263.0(5), wR2=0.0709, 1603 F² values, 64 variables for Lu_13.94Ni_3.07In_2.99. The RE₁₄Ni₃In₃ indides show significant Ni/In mixing on the 4c In1 site. Except the gadolinium compound, the RE₁₄Ni₃In₃ intermetallics also reveal RE/In mixing on the 4c RE1 site, leading to the refined compositions. Due to the high rare earth metal content, the seven crystallographically independent RE sites have between 9 and 10 nearest RE neighbors. The RE₁₄Ni₃In₃ structures can be described as a complex intergrowth of rare earth-based polyhedra. Both nickel sites have a distorted trigonal-prismatic rare earth coordination. An interesting feature is the In2-In2 dumb-bell at an In2-In2 distance of 304 pm (for Gd₁₄Ni_3.29In_2.71). The crystal chemical peculiarities of the RE₁₄Ni₃In₃ indides are briefly discussed.     

Synthesis and characterization of fluorous (S)- and (R)-1-phenylethylamines that effect heat facilitated resolution of (±)-2-(8-carboxy-1-naphthylsulfinyl)benzoic acid via diastereomeric salt formation and study of their circular dichroism

Perfluoroalkyl- or nonafluoro-tert-butoxy-alkyl-substituted enantiopure amines having the structure PhCHCH₃(NR¹R²) [R¹ = H, CH₃; R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃; R¹ = R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃] are obtained in high yields, when (S)-(−)-1-phenylethylamine is reacted with readily accessible alkylating reagents or fluorous 2° amines (R¹ = H; R² = (CH₂)₃C₈F₁₇, (CH₂)₂OC(CF₃)₃) are methylated in a Leuckart-Wallach reaction. The solubility patterns of these novel chiral amines and their hydrochlorides are qualitatively described for a broad spectrum of solvents and the fluorous partition coefficients of the free bases are determined by GC. A novel method for the resolution of enantiomers is disclosed here, which involves the use a half-equivalent of the selected resolving agent in solvent water that displays low solubility for the crystalline diastereomeric salt(s) formed even at temperatures near to its boiling point. Compound (S)-(−)-PhCHCH₃[NH(CH₂)₃C₈F₁₇] is found to satisfy all the latter conditions and successfully used for the heat facilitated resolution of the title racemic acid. The circular dichroism (CD) spectra of six novel fluorous (S)-(−)-1-phenylethylamine derivatives are measured in ethanol, trifluoroethanol and hexafluoropropan-2-ol and discussed in detail.     

Self-assembly behavior of fluorocarbon-end-capped poly(glycerol methacrylate) in aqueous solution

Well-defined perfluoroalkyl-terminated poly(glycerol methacrylate) (R _F-PGMA) semitelechelics are prepared by atom transfer radical polymerization and copper(I)-catalyzed alkyne–azide cycloaddition reaction. R _F-PGMA has a similar architecture as the well-studied perfluorinated poly(ethylene oxide) (R _F-PEO) semitelechelics but bears two hydroxyl groups on each glycerol methacrylate unit. Because of the strong hydrophobic interaction of the perfluoroalkyl group, R _F-PGMA semitelechelics self-associate to form core–corona spherical micelles in water above the critical micellization concentration (cmc) which depends on poly(glycerol methacrylate) (PGMA) content and temperature. For comparison, the R _F-PEO semitelechelics with the same perfluoroalkyl terminal group as R _F-PGMA are also prepared. The cmc values of R _F-PGMA semitelechelics are found to increase with increasing temperature in water, which is opposite to the tendency of R _F-PEO semitelechelics. According to the thermodynamic studies, the micellization process of R _F-PGMA in aqueous solution is driven by both a negative enthalpy and an increase of entropy, whereas the micellization of R _F-PEO is an entropy-driven process exhibiting a positive micellization enthalpy. This striking different behavior originates from intra-/intermolecular hydrogen bonds between the hydroxyl groups of the PGMA chains. These strong inter- and intramolecular hydrogen bonds between PGMA segments lead to a self-aggregation of R _F-PGMA evident in temperature-dependent ¹H and ¹⁹F NMR spectroscopy and dynamic light scattering measurements.     

Determination of pKR+ values for cyclobutadieneiron tricarbonyl-substituted carbocations

pK_R⁺ values for a series of cyclobutadieneiron tricarbonyl-substituted carbocations have been determined by a Hammett-Deno indicator acidity study utilizing trifluoroacetic acid-water solutions. The results show that these carbocations are considerably more stable than a variety of similar organic and organometallic carbocations but less stable than the corresponding ferrocene systems.     

Fluorinated nitroxides as ESR probes of solvation

Some newly synthesized fluorinated nitroxides, such as t-butyl perfluoroalkyl nitroxides Bu^tN(O) R_f (R_f=CF₃, 5; C₂F₅, 6; n-C₃F₇, 7) and s-butyl perfluoroacyl nitroxides Bu^sN(O) COR_f (R_f=CF₃, 9; n-C₃F₇, 10) have been employed as ESR probes of solvation in different common organic solvents. In aprotic solvents, the measured a_N values for each of the nitroxyl probes show a linear correlation with the cybotactic polar solvent parameters E_T (Dimroth) and Z (Kosowar), i.e. a_N=bE_T+c, and a_N=b′Z+c′. The physical significance for the slope (b or b′), the slope×E_T or slope×Z, the extrapolated intercept on a_N axis, c or c′, are linked, respectively, to the sensitivity of a specific nitroxide toward solvation, the magnitude of the overall solvation effect on the a_N value, and the intrinsic a_N value of each nitroxide in the ideal gaseous state. The intercept on the a_N axis may also serve as a new measure of electronegativity for perfluoroalkyl groups, CF₃, C₂F₅, n-C₃F₇, and perfluoroacyl groups, CF₃CO, n-C₃F₇CO. In protic solvents, i.e. alcohols and carboxylic acids, however, a_N values of all the probes, kept almost no change with the increase in E_T and Z. Furthermore, the plots of a_N versus non-cybotactic solvent constants, such as dipolar moment (μ) and dielectric constant (ε), all show random variations.     

Fluorure d'hydrogène liquide: etude du comportement chimique et électrochimique du pérylène: Niveau d'acidité du solvant en milieu basique et tamponné en pH par BF3/BF4−

The dissolution of perylene in liquid HF containing NaF at the concentration 10^?1M leads to the following species: Pn, P⁺ and PnH⁺. In basic medium ([NaF]=1 M) only Pn and P⁺ are present: the radical cation P⁺ is due to the chemical oxidation of perylene by the solvent. The reversible electrochemical oxidation of P⁺ can take place: P⁺-ePn²⁺ and the corresponding normal potential does not depend on the activity of fluoride ions in the solvent. The acidity function R(H) of the solvent has been measured at 0°C in basic medium ([NaF]=1 M) and in slightly acidic media buffered by the couple BF₃/BF₄^?; the corresponding values are R(H)=?13 and R(H)=?19.4.     

A simple molecular model of adsorption chromatography XIV. RF or RM? Secondary retention effects in thin-layer chromatography

Summary It is demonstrated that although the R_F values are directly related to the separations obtained, the R_M values are more convenient in the theory of optimization of chromatograpohic systems. Graphs for direct plotting of R_F values in the R_M scale are shown in both logarithmic and linear solvent composition scale. The effects of preadsorption of the solvent vapours and of simultaneous partition betwen the mobile and the stagnant developing solvent on the retention vs. compostion plots are illustrated. Examples are shown for crossing retentions vs. solvent composition plots.Part XIII: ref [1].     

Structure and Properties of GdTMg (T=Pd, Ag, Pt)

The title compounds were prepared by reacting the elements in sealed tantalum tubes in a water-cooled sample chamber in a high-frequency furnace. X-ray powder and single-crystal investigations showed isotypism with the ZrNiAl type, space group P&6macr;2m: a=750.1(1) pm, c=404.10(4) pm, wR2=0.0703, 250 F² values, 14 parameters for GdPdMg, a=768.0(2) pm, c=419.92(9) pm, wR2=0.0579, 261 F² values, 16 parameters for GdAgMg, and a=738.0(1) pm, c=409.02(5) pm, wR2=0.0742, 244 F² values, 14 parameters for GdPtMg. The structures contain two crystallographically different transition metal (T) sites which both have a tricapped trigonal prismatic coordination: [T(1)Gd₆Mg₃] and [T(2)Mg₆Gd₃]. Together the transition metal and magnesium atoms build three-dimensional networks in which the gadolinium atoms fill distorted hexagonal channels. The magnesium position of the silver compound shows a small degree of magnesium/silver mixing resulting in the composition GdAg_1.06(1)Mg_0.94(1) for the crystal investigated. The magnetic properties of all compounds were investigated using AC and DC susceptibility as well as ¹⁵⁵Gd Mössbauer spectroscopy measurements. All investigated materials show irreversibilities between field cooled and zero-field-cooled DC magnetizations and magnetic hysteresis behavior as is typical for ferromagnets. The remanent magnetizations and coercive fields are relatively small. The Curie temperatures were determined from inflection points of the experimental susceptibilities. Additional anomalies below the ferromagnetic transitions suggest spin-reorientation processes.     

Solvent effect on radical homo- and copolymerization of di-2-[2-(2-methoxyethoxy)ethoxy]ethyl itaconate

Solvent effect on homo- and copolymerization of di-2-[2-(methoxyethoxy)ethoxy]ethyl itaconate (DMEI) was studied at 50 °C using dimethyl 2,2^′-azobisisobutyrate as radical initiator. The polymerization rate (R_p) highly depended on the kind of solvent; 19 solvents were used. The highest R_p (in 1-tetradecanol) is 13 times the smallest (in chloroform). On the other hand, the solvents did not exert as great an effect on the molecular weight of the resulting polymers. The propagation rate constant (k_p) was determined in 15 different solvents by means of ESR spectroscopy. The highest k_p (4.5 l/mol s in toluene) is 5.6 times the lowest (0.8 l/mol s in chloroform). A noticeable solvent effect was also observed in the copolymerization of DMEI (M₁) and styrene (M₂), where nine solvents were used. The highest r₁ (0.46 in 1-butanol) is about 6 times the lowest (0.08 in methanol). The r₂ value falls in the range of 0.2 (dimethyl sulfoxide) and 0.52 (benzene). The solvent effects thus observed were analyzed according to the linear solvation energy relationship proposed by Taft and co workers.     

The role of complex formation in partition paper chromatography

Further information of the possible effects of chemical reaction on differential ionic movement in partition paper chromatography was obtained by developing chromatograms of fifteen inorganic cations with alcoholic solvents containing varying concentrations of disodium ethylenediaminetetraacetate.An examination of these chromatograms indicated that variations in the concentrations of E.D.T.A. in the solvent or the presence of free acid or ammonia resulted in marked changes in R_F values and spot areas.It is therefore suggested that care should be taken in interpreting the results of any chromatograms developed with solvents capable of chemical interaction with the “spotted” solute.     

Rare earth metal-rich indides RE14Rh3−xIn3 (RE=Y, Dy, Ho, Er, Tm, Lu)

The rare earth (RE) metal-rich indides RE₁₄Rh_3-xIn₃ (RE=Y, Dy, Ho, Er, Tm, Lu) can be synthesized from the elements by arc-melting or induction melting in tantalum crucibles. They were investigated by X-ray diffraction on powders and single crystals: Lu₁₄Co₃In₃ type, space group P4₂/nmc, Z=4, a=961.7(1), c=2335.5(5) pm, wR2=0.052, 2047 F² values, 62 variables for Y₁₄Rh₃In₃, a=956.8(1), c=2322.5(5) pm, wR2=0.068, 1730 F² values, 63 variables for Dy₁₄Rh_2.89(1)In₃, a=952.4(1), c=2309.2(5) pm, wR2=0.041, 1706 F² values, 63 variables for Ho₁₄Rh_2.85(1)In₃, a=948.6(1), c=2302.8(5) pm, wR2=0.053, 1977 F² values, 63 variables for Er₁₄Rh_2.86(1)In₃, a=943.8(1), c=2291.5(5) pm, wR2=0.065, 1936 F² values, 63 variables for Tm₁₄Rh_2.89(1)In₃, and a=937.8(1), c=2276.5(5) pm, wR2=0.050, 1637 F² values, 63 variables for Lu₁₄Rh_2.74(1)In₃. Except Yb₁₄Rh₃In₃, the 8g Rh1 sites show small defects. Striking structural motifs are rhodium-centered trigonal prisms formed by the RE atoms with comparatively short Rh-RE distances (271-284 pm in Y₁₄Rh₃In₃). These prisms are condensed via common corners and edges building two-dimensional polyhedral units. Both crystallographically independent indium sites show distorted icosahedral coordination. The icosahedra around In2 are interpenetrating, leading to In2-In2 pairs (309 pm in Y₁₄Rh₃In₃).     

Thin layer chromatographic studies of anils II. Separation,identification and determination

Thin layer chromatographic behaviour of ten anils was studied on silica gel adsorbent mixed with starch binder with ten solvent systems. Simultaneous separation, identification and determination of ternary mixtures of isomers was stressed. TheR _F increasing order was found to be dependent on the solvent and independent of the degree of saturation of the chamber. The correlations ofR _F with _max and (C=O) of isomers were established and used in their identification. Six anils were separated in methanol—benzene (11).     

Resolution of PTH-amino Acids in Three New Solvents on Zn,Cd, Hg Impregnated Silica Plates

Abstract

A ten component mixture of PTH-amino acids has been resolved by TLC using impregnated silica plates. Three new solvent systems, CHCl₃ -H₂O-EtOAc(28:1:1), CCl₄-AcOH(19:1) and CHC₃-MeOH-Benzene(19:1:5) were developed and used. The effect of 0.1, 0.2 and 0.5 % concentrations of each of the impregnant (Zn⁺⁺, Cd⁺⁺, Hg⁺⁺ ions) on R_F values was studied.     

The chromatographic separation of a mixture of the chlorides of calcium,strontium, barium and magnesium

The chlorides of calcium, strontium, bitnum and magnesium have been separated on circular paper, using mixed alcohols, containing mcthanol as one of the constituents, as solvents. Approximate R_F values obtained by using ethanol containing 50%, methanol, have been reported     

Asymmetric reduction of aromatic ketones in pyridinium-based ionic liquids

The asymmetric reduction of aromatic ketones has been studied in pyridinium-based room temperature ionic liquids, namely, 1-ethyl-pyridinium tetrafluoroborate, [EtPy]⁺[BF₄]⁻ and 1-ethyl-pyridinium trifluoroacetate, [EtPy]⁺[CF₃COO]⁻. Ionic liquids were employed as solvents, while (R)-BINOL and (R)-BINOL-Br were used as chiral promoters. The effects of solvent, reaction time, temperature, catalyst loading and substituents were investigated. The reduction could be easily carried out in both ionic liquids with lower catalyst loading. 1-Ethyl-pyridinium tetrafluoroborate was recycled and reused efficiently.