Compatibility of polymers with highly energetic materials by DTA

An areal method previously developed by the author for the estimation of kinetic parameters during polymer pyrolyses, i.e., activation energy (E) and reaction order (n), was extended for the assessment of compatibility of various polymers with highly energetic materials by DTA. Thus, reproducible overall values of E and n were estimated for cellulose nitrate and cyclotrimethylene trinitramine and changes in values of these parameters were used as reliable indices for judging compatibility of highly energetic materials in various admixtures of polymers.     

Schnelle Bestimmung von radioaktivem Tellur in Jodpr?paraten-131J

Zusammenfassung Eine Bestimmungsmethode von radioaktivem Tellur in Jod-131-Präparaten wird vorgeschlagen. Zur Trennung der sich teilweise überschneidenden Aktivitäten werden Jod im alkalischen und Tellur im sauren Medium an Quecksilber(I)-chlorid mitgefällt. Die Methode liefert befriedigende Ergebnisse.

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Summary A method for the determination of radioactive tellurium in iodine-131 preparations is proposed. In order to separate the partly overlapping activities iodine is co-precipitated on mercurous chloride in alkaline and tellurium in acid medium. Satisfactory results are obtained.

     

Über die Synthese von substituierten Thieno[3,4—b]chinolin-9(4H)-onen

The synthesis of in position 4 substituted thieno[3.4-b]quinoline-9(4H)-ones (6) by aromatization of 1.4-dihydrothieno[3.4-b]quinoline-9(3H)-ones (4) and attempts to cyclize 4-phenylamino-3-thiophenecarboxylic acid (3c), or derivatives thereof, to compounds of type6 are described.     

Über die Reaktion von CH3N(PCl3)(BCl3) und [(CH3)2NPCl3] [BCl4] mit AsF3

Products of the reaction between CH₃N(PCl₃)(BCl₃) and AsF₃ are BF₃, AsCl₃ and N,N′-dimethyldiazafluorophosphetidine IV. [(CH₃)₂NPCl₃][BCl₄] reacts with AsF₃ to give dimethylaminotetrafluorophosphorane VI. Preparation and NMR data of IV and VI are given.     

Conformational restriction of nucleosides by spirocyclic annulation at C4' including synthesis of the complementary dideoxy and didehydrodideoxy analogues

The concept of spirocyclic restriction, when generically applied to nucleoside mimics, allows for the preparation of diastereomeric pairs carrying either a syn- or anti-oriented hydroxyl at C-5'. Reported herein are convenient synthetic routes to enantiomerically pure 1-oxaspiro[4.4]nonanes featuring fully dihydroxylated end products as well as congeners having dideoxy and didehydrodideoxy substitution patterns. Notable use is made of the capacity for introducing unsaturation in the furanose sector via phenylsulfenylation and the incorporation of uracil and thymine by way of their silylated derivatives under catalysis with stannic chloride.     

pi-Facial stereoselectivity in Diels-Alder cycloadditions to 1-oxaspiro[4.5]deca-6,9-dien-8-one. The strong directive effect of ether oxygen in a cross-conjugated ketone setting

[reaction: see text] The title compound 1, prepared from 1,4-cyclohexanedione monoethylene ketal, was treated with several reactive dienes, including diphenylisobenzofuran and 9,10-dihydro-11,12-dimethylene-9,10-ethanoanthracene. These [4 + 2] cycloadditions proceed with a strong kinetic bias for bonding to the dienophile from the direction syn to the tetrahydrofuranyl oxygen and consequently hold value in stereoselective synthesis.     

Polymeric Antitumor Agents on a Molecular and on a Cellular Level?

“Chemistry has become a mature science, with all the advantages and handicaps of maturity: harvest is abundant, but many people think future and adventure are to be found elsewhere”^[1a]. This holds true—in 1981, the year of Hermann Staudinger's 100th birthday—for macromolecular chemistry, too. Where can the polymer chemists seek adventures? Unsolved problems in neighboring fields like medicine and molecular biology attract his zeal. Cancer chemotherapy is such a field. Can the polymer chemist help to solve its problems? Polymers may be pharmacologically active as such. If used as carriers, they may, due to their intrinsic properties, influence body distribution, excretion or cell uptake of the pharmaca they carry. Hence, there is a chance for new ways in therapy, including affinity chemotherapy using synthetic macromolecules. Our own body has a perfect biological system for affinity therapy: immune response to infection selectively attacks foreign cells, It is fascinating to observe what the immune system does to a tumor cell which could not escape immune surveillance (cf. Fig. 14). Can these specific cell-cell interactions be mimicked? What do we have to learn for an experimental approach to this adventure? Stable membrane and cell models can be synthesized, a first step towards this goal. Macromolecular chemistry is far from being able to offer satisfying solutions for a specific tumor therapy; striving for it, polymer chemists can learn lots of things. In order to do so, they will have to enter neighboring fields and they will have to be willing and able to cooperate.     

trans,anti,trans-Tetra(spirotetrahydrofuranyl)cyclohexane-1,2-dione. Stereocontrolled Synthesis and Definition of Its Susceptibility to Photoisomerization

The title alpha-diketone (18) has been synthesized in stereocontrolled fashion. The ability to introduce the four contiguous spirocyclic ether oxygens in extended trans fashion rests on the ability of the Normant reagent (ClMgCH(2)CH(2)CH(2)OMgCl) to engage in chelation control during 1,2-addition to an alpha-oxy substituted cyclohexanone. The successful pathway is dependent on the ability of osmium tetraoxide to add (slowly) across the double bond of the cyclohexene precursor. The highly substituted 1,2-cyclohexanedione is quite sensitive to light and rearranges by means of an interesting photoisomerization process to a laterally fused pyran system. A likely mechanistic pathway for this intramolecular isomerization is presented.     

Trends in R-X bond dissociation energies (R = Me, Et, i-Pr, t-Bu; X = H, CH3, OCH3, OH, F): a surprising shortcoming of density functional theory

The performance of a variety of high-level composite procedures, as well as lower-cost density functional theory (DFT)- and second-order perturbation theory (MP2)-based methods, for the prediction of absolute and relative R-X bond dissociation energies (BDEs) was examined for R = Me, Et, i-Pr and t-Bu, and X = H, CH(3), OCH(3), OH and F. The methods considered include the high-level G3(MP2)-RAD and G3-RAD procedures, a variety of pure and hybrid DFT methods (B-LYP, B3-LYP, B3-P86, KMLYP, B1B95, MPW1PW91, MPW1B95, BB1K, MPW1K, MPWB1K and BMK), standard restricted (open-shell) MP2 (RMP2), and two recently introduced variants of MP2, namely spin-component-scaled MP2 (SCS-MP2) and scaled-opposite-spin MP2 (SOS-MP2). The high-level composite procedures show very good agreement with experiment and are used to evaluate the performance of the lower-level DFT- and MP2-based procedures. The best DFT methods (KMLYP and particularly BMK) provide very reasonable predictions for the absolute heats of formation and R-X BDEs for the systems studied. However, all of the DFT methods overestimate the stabilizing effect on BDEs in going from R = Me to R = t-Bu, leading in some cases to incorrect qualitative behavior. In contrast, the MP2-based methods generally show larger errors (than the best DFT methods) in the absolute heats of formation and BDEs, but better behavior for the relative BDEs, although they do tend to underestimate the stabilizing effect on BDEs in going from R = Me to R = t-Bu. The potentially less computationally expensive SOS-MP2 method offers particular promise as a reliable method that might be applicable to larger systems.