A statistical mechanical treatment of high polymer solutions has been carried out on the basis of an idealized model, originally proposed by Meyer, which is analogous to the one ordinarily assumed in the derivation of the ``ideal'' solution laws for molecules of equal size. There is obtained for the entropy of mixing of n solvent and N linear polymer molecules (originally disoriented), ΔS=−k[(n/β) ln v1+N ln v2] where v1 and v2 are volume fractions and β is the number of solvent molecules replaceable by a freely orienting segment of the polymer chain. This expression is similar in form to the classical expression for equal‐sized molecules, mole fractions having been replaced by volume fractions. When the disparity between the sizes of the two components is great, this expression gives entropies differing widely from the classical values, which accounts for the large deviations of high polymer solutions from ``ideal'' behavior. The entropy of disorientation of a perfectly arranged linear polymer is found t...

Thermodynamics of High Polymer Solutions

The Conservation of Orbital Symmetry

The study of biomolecules in their native environments is a challenging task because of the vast complexity of cellular systems. Technologies developed in the last few years for the selective modification of biological species in living systems have yielded new insights into cellular processes. Key to these new techniques are bioorthogonal chemical reactions, whose components must react rapidly and selectively with each other under physiological conditions in the presence of the plethora of functionality necessary to sustain life. Herein we describe the bioorthogonal chemical reactions developed to date and how they can be used to study biomolecules.

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Bioorthogonal Chemistry: Fishing for Selectivity in a Sea of Functionality

The chemistry of heterocyclic carbenes has experienced a rapid development over the last years. In addition to the imidazolin-2-ylidenes, a large number of cyclic diaminocarbenes with different ring sizes have been described. Aside from diaminocarbenes, P-heterocyclic carbenes, and derivatives with only one, or even no heteroatom within the carbene ring are known. New methods for the synthesis of complexes with N-heterocyclic carbene ligands such as the oxidative addition or the metal atom template controlled cyclization of β-functionalized isocyanides have been developed recently. This review summarizes the new developments regarding the synthesis of N-heterocyclic carbenes and their metal complexes.

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

In the investigation of efficient chemical transformations, the carbon-carbon bond-forming reactions play an outstanding role. In this context, organocatalytic processes have achieved considerable attention. 1 Beside their facile reaction course, selectivity, and environmental friendliness, new synthetic strategies are made possible. Particularly, the inversion of the classical reactivity (Umpolung) opens up new synthetic pathways. 2 In nature, the coenzyme thiamine (vitamin B1), a natural thiazolium salt, utilizes a catalytic variant of this concept in biochemical processes as nucleophilic acylations. 3 The catalytically active species is a nucleophilic carbene. 4

Organocatalysis by N-Heterocyclic Carbenes

Über hochpolymere Verbindungen, 127. Mitteil.: Über osmotische Bestimmungen an Lösungen mit stab- und kugelförmigen Teilchen

Es gibt nicht nur eine Zellulose, sondern eine polymevhomologe Reihe derselben. Die physikalischen Eigenschaften der naturlichen und technischen Zellulosen hangen vom Polymerisationsgrad ihrer Makromolekule und weiter von deren jadenformiger Gestalt ab. Durch den Nachweis des makromolekularen Baues der Zellulosen findet ihr chemisches und physikalisches Verhalten eine Erklarung. Lignin dagegen ist kein hochpolymerer Stoff.

Hermann Staudinger

Papers

Über hochpolymere Verbindungen, 127. Mitteil.: Über osmotische Bestimmungen an Lösungen mit stab- und kugelförmigen Teilchen

Über hochpolymere Verbindungen

Über hochpolymere Verbindungen. 51. Mitteilung. Über Polymerisation und Autoxydation

Über Ketene. 6. Mitteilung: Keten

Über aliphatische Diazoverbindungen