Optical activity induced by helical arrangements of tryptamine and 4-chlorobenzoic acid in their cocrystal

Optical rotatory powers of chiral cocrystals formed from the achiral molecules tryptamine and 4-chlorobenzoic acid were determined by the HAUP (high accuracy universal polarimeter) method. These cocrystals belonged to space group P2(1)2(1)2(1), and their absolute configuration was confirmed by the Flack parameter. In the M-crystal, 2-fold helical arrangements are formed in a counterclockwise direction between the two components through the quaternary ammonium salt bridge, hydrogen bond, and the aromatic pi-piinteraction along the c axis, while clockwise helices alone exist in the P-crystal. Large rotatory powers rho(3)(M) = -355 and rho(3)(P) = +352 deg mm(-)(1) were obtained along the c axis in the M- and P-crystal, respectively, at 632.8 nm and 303 K. The magnitude was 10 to 100 times larger than those for ordinary organic crystals. Further, it was confirmed that the negative sign was induced by the counterclockwise helical structures and the positive sign by the clockwise helices. In contrast, the rotations along the a and b axis which are in perpendicular directions to the screw axis were rho(1)(M) = +138, rho(1)(P) = -140 deg mm(-)(1), and rho(2)(M) = -56, rho(2)(P) = +58 deg mm(-)(1), much smaller than rho(3)(M) and rho(3)(P) . The results revealed that the helically arranged aromatic pi electrons as well as the helical ionic and hydrogen bond networks in the crystal contributed to the enhancement of the magnitude of these rotations.     

Extraction of tetrafluoroborate with crown ethers and its application to silicate rock analysis

Summary The extraction behaviour of tetrafluoroborate with crown ethers was studied. A high distribution ratio of tetrafluoroborate is obtained by extraction with dicyclohexano-18-crown-6 (DC18C6) in an organic solvent of high dielectric constant from potassium fluoride solution. The molar ratios of crown ether to KBF₄ in the extracted species are probably 1:1 for DC18C6, dibenzo-18-crown-6 and 18-crown-6, and 2:1 for benzo-15-crown-5 and 15-crown-5. The flow-injection extraction-spectrophotometric determination of tetrafluoroborate with Brilliant Green was worked out. Many rock reference samples were analyzed for boron (1–150 ppm).     

An efficient preparation and spectroscopic and electrochemical properties of quinodimethane derivatives with four 3-(methoxycarbonyl)azulen-1-yl groups

Reaction of methyl 1-azulenecarboxylate (8) with terephthalaldehyde (9) in acetic acid in the presence of hydrochloric acid at 25 °C for 2 h gives 1,4-bis[bis(3-methoxycarbonyl-1-azulenyl)methyl]benzene (12), in 93% yield, which upon oxidation with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in dichloromethane in the presence of hexafluorophosphoric acid at 25 °C for 1 h affords the dicarbenium-ion compound 15 in 94% yield. Furthermore, reduction of 15 with zinc powder in a mixed solvent of acetonitrile and chloroform at 25 °C for 1 h yields the target quinodimethane 18 in 90% yield. Similarly, as in the case of 18, the quinoid compounds 19 and 20 can be derived from the dicarbenium-ion compounds 16 and 17, quantitatively. A facile preparation as well as spectroscopic and electrochemical properties of 15-20 is reported.     

Electronic structures of aromatic amine N-oxides

The electronic structures of heterocyclic amine N-oxides, nitrones, and nitrile N-oxides were systematically studied by the Pariser-Parr-Pople method. In addition, the intensity of n- ^* transition pertinent to conjugated N-oxide systems has been calculated. The results of these calculations were compared with the experimental ones reported hitherto and also carried out in the present work. The electronic structure and spectra of aromatic amine N-oxides were thus discussed in detail.

---

Zusammenfassung Die elektronische Struktur heterozyklischer Amin-N-Oxide, Nitrone und Nitril-N-Oxide wird systematisch mit Hilfe der Pariser-Parr-Pople-Methode untersucht. Au\erdem wurde die IntensitÄt von n- ^*-übergÄngen konjugierter N-Oxide berechnet. Die Resultate wurden mit bekannten sowie eigenen experimentellen Ergebnissen verglichen. Die Elektronenstruktur und die Spektren aromatischer Amin-N-Oxide wurden so im Detail diskutiert.

---

Résumé La structure électronique d'amine N-oxydes, de nitrones, et de nitrile N-oxydes ont été étudiés systématiquement par la méthode de Pariser-Parr-Pople. De plus, l'intensité de la transition n- ^* des systémes N-oxydes conjugués a été calculée. Les résultats de ces calculs ont été comparés aux résultats expérimentaux rapportés précédemment et également à ceux du présent travail. La structure électronique et le spectre des N-oxydes d'amines aromatiques ont ainsi été discutés en détail.

---

---

Presented at the 21st (Osaka, April 1968) Annual Meeting of the Chemical Society of Japan, and the Symposium of Structure Chemistry and the Electronic State of Molecules (Tokyo, October 1968).     

Ammonia synthesis by means of plasma over MgO catalyst

Ammonia synthesis from H₂-N₂ mixed gas was studied at room temperature in a glow-discharge plasma in the presence of metals or metal oxides. Magnesia (MgO) and calcia (CaO), which are oxides with solid basicity, revealed catalytic activity in the plasma synthesis of ammonia, although they are catalytically inactive in industrial ammonia synthesis. The acidic oxides (Al₂O₃, WO₃, and SiO₂-Al₂O₃) lead to the consumption of the reactant, i.e., the H₂-N₂ mixed gas. No ammonia was isolated. Metal catalysts showed higher activity than the above basic oxides. They have, however, different activities. The reaction was faster over the active materials than over sodium chloride (NaCl) or glass wool or in a blank reactor without any catalyst.     

Approaching over 10 000‐fold sensitivity increase in chiral capillary electrophoresis: Cation‐selective exhaustive injection and sweeping cyclodextrin‐modified micellar electrokinetic chromatography

A novel and simple method that combines an online concentration technique with an enantioseparation technique for capillary electrophoresis—namely, cation‐selective exhaustive injection and sweeping cyclodextrin‐modified micellar electrokinetic chromatography (CSEI‐sweeping CD‐modified MEKC)—realizes the effective enantioseparation of cationic analytes while keeping a significant increase of detection sensitivity. This technique consists of a slight modification of the basic CSEI‐sweeping MEKC. The main idea is to simply add an anionic CD as a chiral selector into the micellar buffer including sodium dodecyl sulfate, but not to change any other buffers in order to preserve the online concentration mechanism. When applied to analysis of the street drug, methamphetamine, the method achieved not only a baseline enantioseparation but also limits of detection (LODs; S/N = 3) of 70–90 pg/mL (ppt) for each isomer. This translates to a more than 10 000‐fold improvement compared to the LODs by the usual injection method. The present technique, which was made from a slight modification of CSEI‐sweeping MEKC, would give an attractive approach that is applicable to almost any analytes for which CSEI‐sweeping MEKC is applicable; all that is required is the selection of an appropriate anionic CD to be added to the micellar buffer.     

Influence of the Polymer/Inorganic Filler Interface on the Mechanical,Thermal, and Flame Retardant Properties of Polypropylene/Magnesium Hydroxide Composites

The relationship between the interface structure and the macroscopic properties of composites composed of isotactic polypropylene (iPP) and magnesium hydroxide (MH) was investigated with a focus on mechanical properties, thermal stability, and flame retardancy. Surface treatment of MH was carried out using dodecanoic acid (DA) and dodecylphosphate (DP), both of which interacted with MH to form submonolayer coverages. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that both organic reagents adhere to the MH surface via ionic interactions. Even low amounts of organic reagents on the MH surface were sufficient to improve the mechanical, thermal, and flame retardant properties of the composites. The incorporation of 1.8 wt% of DP in (70/30) iPP/MH-DP composite decreased the peak heat release rate (PkHRR) to 39% compared with that of neat iPP. Since the effects of DA with the same dodecyl chains were not significant, it is concluded that the phosphate groups in DP provide flame retardancy.     

Preparation,molecular structures,and characteristic properties of (E)-1-(2-furyl)- and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylenes and (E)-1-(3-furyl)- and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylenes

Wittig reactions of 2-furaldehyde (20) [and thiophene-2-carbaldehyde (21)] with (3-guaiazulenylmethyl)triphenylphosphonium bromide (19) in ethanol containing NaOEt at 25 °C for 24 h under argon give (E)-1-(2-furyl)-2-(3-guaiazulenyl)ethylene (22E) and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylene (23E) in 53 and 36% yields. Similarly, Wittig reactions of 3-furaldehyde (29) [and thiophene-3-carbaldehyde (30)] with 19 under the same reaction conditions as for 20 and 21 afford (E)-1-(3-furyl)-2-(3-guaiazulenyl)ethylene (31E) and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylene (32E) in 32 and 46% yields. Molecular structures and characteristic properties as well as preparation of the title E (i.e., one of the geometrical isomers) forms, with a view to comparative study, are reported. Moreover, reactions of those conjugated π-electron systems with TCNE (=tetracyanoethylene) in benzene [and in DMF (=N,N-dimethylformamide)] at 25 °C for 24 h under argon yield unique products, possessing interesting molecular structures, respectively, whose characteristic properties and crystal structures are documented, also.     

Thermo-responsive polymer brush-grafted porous polystyrene beads for all-aqueous chromatography

Poly(N-isopropylacrylamide) (PIPAAm) brush-grafted porous polystyrene beads with variable grafted polymer densities were prepared using surface-initiated atom transfer radical polymerization (ATRP) for applications in thermo-responsive chromatography. Utilization of these grafted beads as a stationary phase in aqueous chromatographic analysis of insulin provides a graft density-dependent analyte retention behavior. The separations calibration curve on PIPAAm-grafted polystyrene was obtained using pullulan standards and exhibited inflection points attributed to analyte diffusion into bead pores and partitioning into grafted PIPAAm brush surfaces. Presence of these inflection points supports a separation mechanism where insulin penetrates pores in polystyrene beads and hydrophobically interacts with PIPAAm brushes grafted within the pores. Control of PIPAAm brush graft density on polystyrene facilitates effective aqueous phase separation of peptides based on thermally modulated hydrophobic interactions with grafted PIPAAm within stationary phase pores. These results indicated that PIPAAm brush-grafted porous polystyrene beads prepared by surface-initiated ATRP was effective stationary phase of thermo-responsive chromatography for aqueous phase peptide separations.     

Preparation, crystal structure, and spectroscopic, chemical, and electrochemical properties of (2E,4E)-4-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-1,3-butadiene compared with those of (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene

Wittig reaction of 3-[4-(dimethylamino)phenyl]propanal (5) with (3-guaiazulenylmethyl)triphenylphosphonium bromide (4) in ethanol containing NaOEt at 25 °C for 24 h under argon gives the title (2E,4E)-1,3-butadiene derivative 6E in 19% isolated yield. Spectroscopic properties, crystal structure, and electrochemical behavior of the obtained new extended π-electron system 6E, compared with those of the previously reported (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene (12), are documented. Furthermore, reaction of 6E with 1,1,2,2-tetracyanoethylene (TCNE) in benzene at 25 °C for 24 h under argon affords a new Diels-Alder adduct 8 in 59% isolated yield. Along with spectroscopic properties of the [π4+π2] cycloaddition product 8, the crystal structure, possessing a cis-3,6-substituted 1,1,2,2-tetracyano-4-cyclohexene unit, is shown. Moreover, reaction of 6E with (E)-1,2-dicyanoethylene (DCNE) under the same reaction conditions as the above gives no product; however, this reaction in p-xylene at reflux temperature (138 °C) for four days under argon affords a new Diels-Alder adduct 9 in 54% isolated yield. Although reaction of 6E with DCNE in toluene at reflux temperature (110 °C) for four days under argon provides 9 very slightly, reaction of 6E with dimethyl acetylenedicarboxylate (DMAD) in toluene at reflux temperature for two days under argon yields a new Diels-Alder adduct 10, in 58% isolated yield, which upon oxidation with MnO₂ in CH₂Cl₂ at 25 °C for 1 h gives 11, converting a (CH₃)₂N-4″ into CH₃NH-4″ group, in 37% isolated yield. The crystal structure of 11 supports the molecular structure 10 possessing a partial structure cis-3,6-substituted 1,2-dimethoxycarbonyl-1,4-cyclohexadiene. The title basic studies on the above are reported in detail.