Binding energies of ionized donor–exciton complexes in polar crystals

Binding energies of ionized donor–exciton complexes in crystals of CdSe, CdTe, and ZnSe are calculated using the most realistic effective potentials available for the electron–hole interaction.     

Differential thermal analysis of fluxed melts and its application to the system NiFe2O4-BaO-B2O3

The application of DTA to fluxed melts is discussed, and an apparatus for the determination of the solubility of crystalline materials in molten solutions is described. An exploratory study of the crystallization of nickel ferrite from barium borate fluxes is also described, and solubility curves are presented for fluxes which favour crystal growth. The heat of solution of nickel ferrite was found to be 73 ± 2 Kjoule mole^–1.

---

Zusammenfassung Es wurde über die Anwendung der DTA Methode bei der Untersuchung von Flußmittel enthaltenden Schmelzen berichtet und ein Apparat zur Bestimmung der Löslichkeit von kristallinischen Substanzen in Flüssen beschrieben. Eingehend wurden die Kristallisation von Nickelferrit aus Bariumborat-Flüssen untersucht und Löslichkeitskurven für den Kristallwachstum begünstigende Flüssen gegeben. Die Lösungswärme von Nickelferrit betrug 73 ± 2 Kjoule Mol^–1.

---

Résumé On a décrit l'application de la méthode ATD à l'étude des fusions avec fondant et un appareil adapté à la détermination de la solubilité des substances crystallines dans les fondants. On a étudié la cristallisation de ferrite de nickel des flux de borate de baryum. Des courbes de solubilité pour des flux favorisant les grossissement des cristaux sont présentées. La chaleur de solution du ferrite de nickel a été trouvée 73 ± 2 kjoule mole^–1.

---

A ( ). , . 73±2 ^–1.

     

The preparation of some reactive 1,6-disubstituted perfluorohexanes

Reactive 1,6-disubstituted perfluorohexanes have been prepared $\text{via}$ the reaction of 1,6-$\text{bis}$(dimethylhydrosilyl)-perfluorohexanes with alkyllithium and Grignard reagents. The resulting species may be derivatized in the same manner as organolithium reagents, but are appreciably more stable than the 1,6-dilithioperfluorohexane which is presumably generated by the halogen-metal exchange between an alkyllithium reagent and Br(CF₂)₆Br. 1,6-bis(Bromomagnesium)-perfluorohexane was also prepared in good yield by a halogen-metal exchange reaction.     

First Synthesis of 3-Mercapto-2(1H)-pyridinone, a Simple Disubstituted Pyridine Useful for Synthesis of the 4-Azaphenoxathiine Ring System and Its Novel Diazaphenoxathiine Analogs: 1,6-Diazaphenoxathiine and 2,6-Diazaphenoxathiine(1)

3-Mercapto-2(1H)-pyridinone (1) can be synthesized in three simple high-yielding steps from readily available 2-tert-butylthiazolo[4,5-b]pyridine (2). Its disodium salt condenses with o-chloronitrobenzene, 2-chloro-3-nitropyridine, and 3-chloro-4-nitropyridine 1-oxide to give respectively 4-azaphenoxathiine (10), 1,6-diazaphenoxathiine (12), and 2,6-diazaphenoxathiine 2-oxide (14) which reduces to 2,6-diazaphenoxathiine (15). The structures of these previously unreported azaphenoxathiine systems were confirmed by assignment of their respective (13)C NMR spectra.     

Growth and decay tables for radium-225 and actinium-225

To facilitate the use of²²⁵Ra as a yield tracer in radiochemical assays of²²⁶Ra and²²⁸Ra, growth and decay tables for²²⁵Ra, and its daughter²²⁵Ac, have been computed.     

Observations on the reduction of aryl nitro groups with palladium-sodium borohydride

The reduction of aryl nitro groups by the palladium-sodium borohydride system can be controlled in some instances to give products differing from those of catalytic hydrogenation. With six equivalents of borohydride added to the catalyst 2,2′-dinitrobiphenyl formed only 2,2′-diaminobiphenyl. With added sodium hydroxide and varying amounts of borohydride and catalyst, the reduction can be controlled to give benzo[c]cinnoline, benzo[c]cinnoline 5-oxide or benzo[c]cinnoline 5,6-dioxide. In a closed system, the reagents reduce both the nitro and olefin functional groups in 6-nitro-5,8-dimethoxy-1,4-dihydro-1,4-ethano-naphthalene. In an open flask flushed with argon, the reduction is confirmed to the nitro group. Reduction of 2-chloro and 4-chloronitrobenzene with palladium-borohydride gives substantial yields of the appropriate chloroanilines. In contrast, hydrogen and palladium give aniline as the major product from each of these. These results suggest that the addition of sodium borohydride to palladium on carbon produces a reductive entity differing from that of catalytic hydrogenation.     

Self-repairing polymers: poly(dioxaborolane)s containing trigonal planar boron

The molecular weight of poly(dioxaborolane)s can be controlled during the polymerization reaction or through post-polymerization processing in such a manner that hydrolytic damage to these materials may be repaired, thereby regenerating the polymer.     

OZONE, MIDDLE ULTRAVIOLET RADIATION AND THE AQUATIC ENVIRONMENT

Marine organisms in the upper layers of the sea may be endangered by increased ultraviolet radiation resulting from declines in the thickness of stratospheric ozone. Evidence supporting this hypothesis includes the fact that wavelengths of potentially damaging ultraviolet radiation can penetrate to ecologically significant depths and laboratory findings that many marine organisms are extremely sensitive to this radiation. Estimated effects of increased ultraviolet radiation on populations of marine organisms range from insignificant to catastrophic. Direct estimation of population effects have not been made, although this is the only adequate measure of the potential impact. The extreme diminution of ozone during the Antarctic spring, coupled with the dynamics of phytoplankton production in this region, may provide conditions suitable for an environmental test of the hypotheses that marine organisms are endangered by reduced stratospheric ozone. There is an urgency to the testing of this hypothesis since these populations may be directly impacted at the present time.     

The crystal and molecular structure of dodecafluorotriphenylene, C18F12

The dodecafluorotriphenylene molecule is considerably distorted from planarity by steric interactions between the “ortho” fluorine atoms which approach to within 2.41 Å of each other (or about 0.3 Å closer than the sum of the van der Waals radii for two fluorine atoms, 2.70 Å).