Publisher Summary This chapter states that the reaction of carbohydrates in alkaline or acidic aqueous solutions results in a myriad of products, many of which have been recognized for well over a century. With the exception of anhydro sugars and oligosaccharides, found as concentration-dependent, equilibrium constituents in acidic solutions, all of the products result from reactions of intermediates. The dehydration reactions initiated by eliminating a hydroxyl group from an enediol are discussed in the chapter. The products of these eliminations are normally transient intermediates, and undergo further reaction. The final products formed are determined by the carbohydrate reacting, the conditions of reaction, and the character of the medium. In the degradation reactions of sugars, major structural differences exist between products and reactants: in acidic solution, pyranoses produce furan compounds; in basic solution, acyclic saccharinic acids are formed. The acyclic enediols produced from acyclic sugars, which are the intermediates in the isomerization, are also the reactive components that initiate the degradation reactions and the dehydration products may be regarded as products of a side reaction of the transformation.

Dehydration Reactions of Carbohydrates

In den letzten Jahren wurde, hauptsachlich bei Bakterien, eine neue Klasse von Desoxyzuckern aufgefunden und — gemeinsam mit den Arbeitskreisen von A. M. Staub und E. Lederer — als 3.6-Didesoxyhexosen aufgeklart. Von den theoretisch moglichen acht Stereoisomeren sind bislang wenigstens funf naturliche Vertreter, darunter zwei Paare von optischen Antipoden, bekannt. Ihre Isolierung, Strukturaufklarung und Synthese sowie Nachweisverfahren werden beschrieben. In Zusammenarbeit mit F. Kauffmann wurden umfangreiche Zuckerbaustein-Analysen von Polysacchariden (O-Antigenen) bei Salmonellen u. a. durchgefuhrt; 3.6-Didesoxy-hexosen treten haufig auf und sind charakteristisch fur bestimmte Serogruppen. Als Bausteine spezifischer Polysaccharide in der bakteriellen Zellwand besitzen die jeweils terminal gebundenen 3.6-Didesoxy-hexosen vielfach immunologische Funktion als determinante (spezifitats-bestimmende) Endgruppen (mit A. M. Staub und R. Tinelli). Dies wurde u. a. durch Darstellung eines kunstlichen Antigens mit Colitose (3-Desoxy-L-fucose) als determinanter Gruppe demonstriert. Die Immunisierung geeigneter Tiere fuhrte nicht nur zu Antikorpern gegen Colitose, sondern auch gegen einige pathogene Bakterien, welche colitose-haltige Zellwand-Polysaccharide bilden (E. coli O 111 u. a.). Einige biochemische und genetische Aspekte im Zusammenhang mit 3.6-didesoxyhexose-haltigen bakteriellen Zellwand-Polysacchariden werden erortert und diskutiert.

3.6-Didesoxy-hexosen - Chemie und Biologie†

Publisher Summary This chapter presents the chemistry of furans and shows that there are still many possibilities for further investigation. Furans undergo electrophilic substitution with exceptional ease, if there are no electron-withdrawing groups in the ring. The decarbonylation of furfural to give furan is best carried out at high temperatures. Catalytic dehydrogenation of dihydrofurans is unsatisfactory as in several cases secondary reactions take place. The addition reaction to the furan ring that has been by far the most studied is certainly the catalytic hydrogenation of the ring. It has been shown in the numerous publications on this reaction that various classes of compounds can be obtained-alcohols, ketones, hydrocarbons, ethers, and others. The chapter explores two elimination processes that go through the furan ring and lead to aromatization. Ring cleavage in the furan system is usually obtained by catalytic hydrogenolysis. The chapter presents the examples of addition reactions and conversion reactions and discusses the oxidative ring opening.

The development of the chemistry of furans, 1952-1963*

I. INTRODUCTION The furfuryl alcohol and furan resins comprise a group of polymeric liquids derived from furfuryl alcohol or compounds containing the basic furan ring structure. As liquids they have viscosities ranging from approximately 100 to 300,000 cP. They can be resinified further by conventional acid catalysis and cured to provide infusible solid products having high hardness, flexural strength, and chemical resistance to most acids, alkalies, and solvents. They may also be converted to flexible solids by cross-linking with suitable catalyses such as polyfunctional amines [1] or by the use of modifying copolymers and controlled curing conditions [2,3].

Polyfurfuryl Alcohol Resins

Renewable agricultural biomass derived chemicals, their modifications and uses have seen multiplicity in numerous applications and important processes with major impacts on the pursuit for eco-sustainability. Such applications range include the energy sector, chemistry, pharmacy, the textile industry, paints and coatings, plastic industry, to name but a few. This field of lignocellulosic derived chemicals interconnects several scientific disciplines ranging from agriculture, biochemistry, engineering, environmental sciences, forestry, pharmacy, medicine, etc. hence making it difficult to have a single expert view on these complicated interactions. Therefore, the idea to create a focused review, specifically, on FA (an important furanic compound) is the main objective of this article. FA and its resultant derivatives exhibits an array of capabilities and fascinating properties in various fields of applications. As a compound or with co-reactants, it finds interesting applications as base and/or intermediate chemical compound, hypergolic rocket fuels, in flame resistant composites and coatings used in aerospace, auto, and the built environment; it also finds application as mortars, cementitious grouts, impregnating materials, and sealants due to its exceptional resistance to common corrosive chemicals such as acids, alkalis and other solvents when it is cross-linked. Coupled with its environmental and economic benefits FA has proved to be a remarkable eco-sustainable bio-derived compound.

Wilhelm Gump

Papers

Über die Aufspaltung des Furfuralkohols und den Mechanismus der Lävulinsäure‐Bildung aus Hexosen