The maximum melting temperatures in strain-crystallized van der waals networks

A theory of strain-crystallization of random networks comprised of stereoregular chains is developed. The crosslinks are assumed to be expelled from crystal cores. For this reason, the rubber is considered to be represented as a random eutectoid copolymer, the thermodynamics of strain crystallisation of which is described by the use of the van der Waals model of networks. The strain dependence of the maximum melting temperatures, the degree of crystallinity and the average thickness of the crystallites calculated are shown to be in fair accord with experimental data.Dedicated Prof. Dr. R. Bonart on the occasion of his 60th birthday.     

Thermodynamische (maximale) Schmelzpunkte von oligomeren und polymeren Einstoff- und Mehrstoffsystemen

Colloid and Polymer Science - Mit Hilfe des Gittermodells von Flüssigkeiten wird in Anlehnung an bekannte Ansätze die Entropie von ideal athermischen polymeren Vielkomponentenmischungen...     

Chlorides, oxochlorides, and oxoacids of 1,8-diphosphanaphthalene: a system with imposed close p...p interaction

Several new 1,8-diphosphanaphthalene oxochloro compounds and oxoacids were prepared and fully characterized. The new compounds are discussed in the broader context with other known congeners to demonstrate the variability of the diphosphanaphthalene scaffolding's bonding patterns. Three principal modes of interaction of the phosphorus moieties were observed in the series: bonding, bridging, and repulsive, resulting respectively in none, moderate, and substantial crowding and distortions. The unexpected dimeric diphosphaacenaphthene anion has been obtained from disproportionative hydrolysis of Nap(PCl(2))(2) (Nap = naphthalene-1,8-diyl).     

New mode of sterically imposed phosphorus hyperco-ordination

The sterically imposed electronic interaction in Nap (POCl2)(PCl4) (Nap = naphthalene-1,8-diyl) results in hyperco-ordination of the P atom by the O donor in the bridging position between the two peri-substituents.     

Demonstration of the utility of DOS-derived fragment libraries for rapid hit derivatisation in a multidirectional fashion

Organic synthesis underpins the evolution of weak fragment hits into potent lead compounds. Deficiencies within current screening collections often result in the requirement of significant synthetic investment to enable multidirectional fragment growth, limiting the efficiency of the hit evolution process. Diversity-oriented synthesis (DOS)-derived fragment libraries are constructed in an efficient and modular fashion and thus are well-suited to address this challenge. To demonstrate the effective nature of such libraries within fragment-based drug discovery, we herein describe the screening of a 40-member DOS library against three functionally distinct biological targets using X-Ray crystallography. Firstly, we demonstrate the importance for diversity in aiding hit identification with four fragment binders resulting from these efforts. Moreover, we also exemplify the ability to readily access a library of analogues from cheap commercially available materials, which ultimately enabled the exploration of a minimum of four synthetic vectors from each molecule. In total, 10–14 analogues of each hit were rapidly accessed in three to six synthetic steps. Thus, we showcase how DOS-derived fragment libraries enable efficient hit derivatisation and can be utilised to remove the synthetic limitations encountered in early stage fragment-based drug discovery.

Fragment-based screening of a shape-diverse collection yielded four hits against three proteins. Up to 14 analogues of each hit were rapidly generated, enabling four fragment growth vectors to be explored using inexpensive materials and reliable synthetic transformations.     

Novel small organo-P-S/Se heterocycles

Oxidative addition of elemental sulfur and selenium to cyclomonocarbatetraphosphines (PhP)4CR2 (R = H, Me) afforded novel five- and four-membered heterocycles PhP(E)CH2PhP(E)E2(E = S, Se) and PhP(Se)CMe2-PhP(Se)Se.     

Universality and individuality as complementary factors to optimize and reproduce cell populations

Irreversible thermodynamics allows us to formulate the law of mass action for a large number of reactions running off in open systems. By applying it to cell populations, these ensembles are supposed to be installed by defined increments. Stationary ensembles are then predicted to be optimized in the sense of thermodynamics of irreversible processes. General relations for describing the cell size distribution or the intracellular length distribution of proteins are deduced. During cell growth and multiplication, the cell size distributions change systematically in the course of time; yet, they are all reproduced by only adjusting the standard energy. This phenomenon is considered to originate with process-dependent constraints according to irreversible thermodynamics characterized by hidden variables. In agreement with the theoretical demands, all the different realizations belong to the same universal cell size distribution. Moreover, the universal stationary cell size distribution is classified by a single parameter, p. It is then of great importance that the stationary size distributions of cells of bacteria, yeast and human melanocytes all belong to the p=3 type, irrespective of the external conditions and of the individual chemical structure of the constituents. Universality also classifies the intracellular length distribution of proteins. The results discussed are enough to uncover as to how the genetically perfect production of the individual constituents and the thermodynamic optimization of the whole cell population are logistically coordinated.     

Zur Kenntnis des Verhaltens der Oxidsulfate der Seltenen Erden gegen Chlorwasserstoff. III. Darstellung und thermisches Verhalten der Chloridsulfate der Seltenen Erden

Treatment of chlorination products of rare earths oxidesulphates with methanol yields chloride-sulphates M^IIIClSO₄ as residues. Thermal decomposition of chloride-sulphates yields oxide-sulphates MO₂SO₄; as intermediates, mixtures of the composition MO₂SO₄? M(SO₄)₃ are obtained.     

Road maps for nitrogen-transfer catalysis: the challenge of the osmium(VIII)-catalyzed diamination

Although the Sharpless dihydroxylation has been used on laboratory and industrial scales for several decades, an analogous osmium-catalyzed diamination is unknown. To explore the reaction of osmium(VIII) oxo-imido complexes with C=C bonds, density functional calculations have been performed. The calculations predict a chemoselective and perispecific [3+2] addition of the NH=Os=NH moiety of diimidodioxoosmium(VIII) to ethylene, yielding dioxoosma-2,5-diazolidine. At first sight, this metallacycle seems extremely stable; it is more stable than diimidoosma-2,5-dioxolane by 40 kcal mol(-1). However, a comparison of the thermodynamic reaction profiles for catalytic model cycles of dihydroxylation, aminohydroxylation, and diamination reveals that, contrary to common belief, the instability of the metal=N bond in the osmium(VIII) imido complex rather than the stability of the metal-N bond in the osmium(VI) intermediate causes most of the energy difference between the metallacycles. Substituents on the substrate have a small effect on the thermodynamic reaction profiles, whereas substituents on the imido ligands allow steric and electronic control of the reaction free enthalpies in the range of up to 25 kcal mol(-1). The results of this study help identify potential challenges in the development of the as-yet hypothetical title reaction and provide a modular concept for exploring novel catalytic routes.