High-fidelity Recognition of Organotrifluoroborate Anions (R−BF3−) as Designer Guest Molecules

The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF₃⁻). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF₃⁻, by cyanostar macrocycles that are size-complementary to the inorganic BF₄⁻ progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K⁺ salts of R−BF₃⁻ anions.     

Miscibility of polyester/nitrocellulose blends: A DSC and FTIR study

The miscibility of polyester/nitrocellulose blends was investigated by differential scanning calorimetry and Fourier-transform infrared (FTIR) spectroscopy. Two nitrocelluloses (NC) derived from wood and having different nitrogen contents (12.62 and 13.42%) were used. On the basis of the glass transition temperature criterion, poly(?-caprolactone) (PCL), poly(valerolactone), poly(ethylene adipate), and poly(butylene adipate) are miscible with nitrocellulose, whereas poly(α-methyl α-propyl β-propiolactone) and poly(α-methyl β-proiolactone) are immiscible. The T_g versus composition curves of PCL/NC blends do not follow a monotone function but exhibit a singular point at a critical PCL volume fraction of 0.51 for NC-1342 and 0.45 for NC-1262 in agreement with Kovacs' theory. A shift of 17 cm^-1 of the carbonyl stretching band was observed with PCL/NC blends and is taken as evidence for hydrogen bonding interaction between the PCL carbonyl group and NC hydroxyl group. The frequency difference between the free hydroxyl absorbance and the absorbances of the hydrogen-bonded species was found to be 85 cm^-1 in pure NC and 125 cm^-1 in PCL/NC blends; it indicates that the average strength of this interaction is stronger than the corresponding self-associated hydrogen bonding in pure NC. The presence of a dipole-dipole interaction between the nitrate-ester groups of NC and the carbonyl groups of the polyesters is reported. The relative strength of the hydrogen bonding and dipole-dipole interactions is discussed and correlated with polymer miscibility.     

Characterization of inclusion complexes of betamethasone-related steroids with cyclodextrins using high-performance liquid chromatography

HPLC was used to study the inclusion complexes formed between various beta- and gamma-cyclodextrins and a series of corticosteroids related to betamethasone. Apparent association constants were measured in acetonitrile-water for a set of 13 steroids. An increase in the stability of the steroid-cyclodextrin complex is observed at lower concentrations of acetonitrile. The effects of the nature of the halide at the 9-position, the location of a double bond within the C-ring, substitution at the 9- and 11-positions, and modification of the D-ring of the steroid backbone were studied. The 11- and 17-positions were found to be critically involved in the inclusion process. Larger apparent association constants were obtained with gamma-cyclodextrin (gamma-CD) than with beta-cyclodextrin (beta-CD) due to the increased diameter of the gamma-CD cavity. Van't Hoff plots were constructed to examine the thermodynamic properties of the inclusion process. Plots constructed using retention factors were found to be nonlinear when gamma-CD was present in the mobile phase. This is due to an increase in the strength of the inclusion complex as temperature decreases. Plots constructed using apparent association constants were linear, indicating that the mechanism of inclusion does not change over the range of temperatures studied (10 to 80 degrees C). Enthalpy-entropy compensation was observed for 11 of the 13 steroids studied. The usefulness of cyclodextrins to achieve the separation of steroids in HPLC is discussed and a practical application for the analysis of a steroid and three potential impurities is described.     

Die quantitative Bestimmung der Sulfons?uren von Phenol, Naphthalin und Anthrachinon durch Chromatographie an S?ulen aus Cellulosepulver

Zusammenfassung Die quantitative Analyse von Sulfonsäuren des Phenols, des Naphthalins und des Anthrachinons durch Säulenchromatographie an Cellulosepulver wird beschrieben. Die einzelnen Säuren werden mit Gemischen aus n-Propanol-Chloroform-Wasser eluiert und alkalimetrisch bestimmt. Von den Phenolsäuren kann man das o- und p-Isomere sowie die Schwefelsäure bestimmen. Von den Naphthalinsulfonsäuren wird der Gehalt an Monound Disulfonsäuren sowie an Schwefelsäure bestimmt. Von den Derivaten des Anthrachinons lassen sich die 1-Sulfon-, sowie 1,5- und 1,8-Disulfonsäuren trennen. Von den nichtkatalytisch sulfonierten Produkten läßt sich der Gehalt an Mono-, an Disulfonsäuren und an Schwefelsäure bestimmen, sowie das Verhältnis zwischen 1- und 2-Anthrachinonsulfonsäuren. Eine Analyse dauert ungefähr 1–3 Std.

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Summary A quantitative analysis of sulphonic acids of phenol, naphthalene and anthraquinone by column chromatography on cellulose powder is described. The separation of the acids is achieved by elution of the sample with a propanol-chloroform-water mixture and the obtained individual acids are estimated by alcalimetric titration. By this method the determination of the para- and ortho-isomers of phenol sulphonic and sulphuric acid is possible. The naphthalenesulphonic acids are also separated and the amounts of sulphuric acid, mono- and disulphonic acids are determined. From the derivates of anthraquinone the separation of 1-sulphonic, 1,5- and 1,8-disulphonic acids is suecesfully performed. In the products obtained by non-catalytical sulphonation the mono-, disulphonic and sulphuric acids may be determined, also the ratio of 1- to 2-anthraquinone sulphonic acids. About 1–3 hours are required for a complete analysis.

     

Beitrag zur Papierchromatographie chlorierter Phenole

Zusammenfassung Es wurde eine chromatographische Methode ausgearbeitet, bei der sich das Papier zwischen zwei Glasplatten befindet und die Probe unmittelbar vor der Front des vorrückenden Lösungsmittels aufgetragen wird. Auf diese Weise gelang es, auch flüchtige Stoffe zu trennen, wie z.B. das o-Chlorphenol, das bei der üblichen Ausführung auch aus dem mit Formamid imprägnierten Papier entwich. Die vollständige Sättigung des Raumes zwischen den Gläsern mit Lösungsmitteldämpfen beeinflußte günstig die Trennung und die Bildung von regelmäßigen, runden Flecken.Von den untersuchten Systemen bewährt sich am besten ein System, bei dem Xylol als bewegliche Phase und Whatman-Papier Nr. 3, imprägniert mit einer 30%igen methanolischen Lösung von Formamid, als stationäre Phase diente. Mit Hilfe dieses Systems ließen sich sämtliche Produkte der direkten Chlorierung von Phenol, außerdem einige mono- und dichlorierte Kresole gut trennen. Aus den R _M -Werten ließ sich ableiten, daß die Beweglichkeit eine additive Funktion der einzelnen Substituenten ist. Die beschriebene Methode wurde zur betriebsmäßigen Überwachung der Phenolchlorierung eingeführt.

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Summary A chromatographic procedure has been worked out for the separation of chlorinated phenols, using paper placed between two glass plates. The-sample is introduced at the front of the advancing solvent. The fact that the space between the two glass plates is completely saturated by solvent vapours enhances the separation and the formation of regular, round spots. The method permits to separate without loss even the more volatile substances, such as phenol, o-chlorphenol, etc.On Whatman 3-paper impregnated with 30% methanolic formamide and with xylene as the mobile phase all products of direct chlorination of phenol and moreover some mono- and dichlorocresols can be separated satisfactorily. It is derived from the R _M -Values that the mobility is an additive function of the single substituents. The method has been introduced for checking industrial phenol chlorination.