Carbohydrates chemical conversions

The carbon cycle, one of the most essential of all biological processes, involves the chemical conversion of carbon dioxide to carbohydrates in green plants by photosynthesis. Animals consume the carbohydrates and, through the metabolic process, reconvert the carbohydrates back into carbon dioxide, which is returned to the atmosphere to continue the cycle. 

Beyond this careful selection of platform chemicals, the production of a number of other polymer building blocks, chemical intermediates, and end products from carbohydrates has been reported. Due to the unique oxygen-rich composition of carbohydrates, their conversion into renewable chemicals that preserve the functional groups is an advantage over the current petroleum and natural gas conversion routes. Biomass conversion with high atom efficiency is a key aspect of the competitive synthesis of chemicals and chemical-based products. 

In this volume we begin with an introduction to identify and assess the value of potential chemical conversions of biomass feedstocks. This is then followed by several chapters from leaders in the field covering various catalytic methods for oxygen-removal and refunctionalization of polyoxygenates, including selective dehydration to multipurpose furan derivatives, carbohydrate retroaldol/... 

Fructose Sugar obtained Irom certain trulls or from the chemical conversion of dextrose (glucose). As 3 substitute for table sugar, because it is sweeter and loss Is needed. Same ealoric and carbohydrate values as mo other pure srrgars. There Is little evidence lo support the use ot fructose tp treating blood sugar disorders. 

Chemical conversion of carbohydrates-including esterification often leads to colour formation. A new work-up procedure is capable of removing the color and byproducts until a near waterwhite product of 45 hazen is obtained. 

Chatteijee, C., Pong, F., Sen, A., 2015. Chemical conversion pathways for carbohydrates. Green Chemistry 17, 40—71. 

The exact processes by which carbohydrates and fats are converted to CO2 and H2 O depend on the conditions and the particular needs of the cell. Each possible route involves a complex series of chemical reactions, many of which are accompanied by the conversion of ADP to ATP. One molecule of glucose, for example, is oxidized to CO2 and H2 O in a sequence of many individual reactions that can convert as many as 36 ADP molecules into ATP molecules H12 Og + 6 O2 + 36 ADP + 36 H3 PO4 6 CO2 + 36 ATP +42 H2 O... 

Electron-transfer reactions occur all around us. Objects made of iron become coated with mst when they are exposed to moist air. Animals obtain energy from the reaction of carbohydrates with oxygen to form carbon dioxide and water. Turning on a flashlight generates a current of electricity from a chemical reaction in the batteries. In an aluminum refinery, huge quantities of electricity drive the conversion of aluminum oxide into aluminum metal. These different chemical processes share one common feature Each is an oxidation-reduction reaction, commonly called a redox reaction, in which electrons are transferred from one chemical species to another. 

The same group has developed the enantiospecffic synthesis of a-hydroxy [5-lactams 224 from readily available carbohydrates (Scheme 9.72) [123]. Microwave-assisted chemical reactions have been utilized for the preparation of these 3-hydroxy-2-azetidinones 224 and their subsequent conversion to enantiomeric forms of intermediates for natural products. 

The initial conversion of light into chemical energy takes place in the thylakoid membrane. Besides the chlorophylls and series of electron carriers, the thylakoid membrane also contains the enzyme adenosine triphosphate (ATP) synthase. The enzymes that are responsible for the actual fixation of C02 and the synthesis of carbohydrate reside in the stroma that surround the thylakoid membrane. The stroma also contains deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and ribosomes that are essential for protein synthesis [37]. 

Looking into the future, we expect that hydrogenation reactions will also be tremendously important for the conversion of renewable resources. Going from carbohydrates to valuable chemicals will require deoxygenating reactions. Thus, hydrogenation of alcohols, aldehydes and carboxylic acids will become very important topics. 

This chapter surveys different process options to convert terpenes, plant oils, carbohydrates and lignocellulosic materials into valuable chemicals and polymers. Three different strategies of conversion processes integrated in a biorefinery scheme are proposed from biomass to bioproducts via degraded molecules , from platform molecules to bioproducts , and from biomass to bioproducts via new synthesis routes . Selected examples representative of the three options are given. Attention is focused on conversions based on one-pot reactions involving one or several catalytic steps that could be used to replace conventional synthetic routes developed for hydrocarbons. 

The catalytic conversion of platform molecules produced by bioconversion of renewables into bioproducts. This is already the basis of many industrial processes, leading to important tonnages of chemicals and polymers from carbohydrates and triglycerides and fine chemicals from terpenes. This approach needs to be extended and process efficiency should be strengthened by designing more active and selective catalysts. 

Special attention is given to the integration of biocatalysis with chemocatalysis, i.e., the combined use of enzymatic with homogeneous and/or heterogeneous catalysis in cascade conversions. The complementary strength of these forms of catalysis offers novel opportunities for multi-step conversions in concert for the production of speciality chemicals and food ingredients. In particular, multi-catalytic process options for the conversion of renewable feedstock into chemicals will be discussed on the basis of several carbohydrate cascade processes that are beneficial for the environment. 

The particular wood species we chose for this study is aspen (Populus tremuloides), which is plentiful in Canada and in the northern U.S.A. The chemical composition we found to be glucan 53.4%, xylan 14.9%, total carbohydrate 79.0%, lignin 17.1% and extractives 3.8%. We would expect total fermentable sugars of about 56% in this sample of aspen in anhydro form (Timell has reported about 60% in another sample (15)) which upon hydrolysis would yield about 1,250 lb wood sugars per ton of wood (dry basis), from the stoichiometry. Theoretical conversion of this sugar to ethanol would yield 640 lb or 81.1 gallons of anhydrous... 

Abstract Polyfunctionality of carbohydrates and their low solubility in conventional organic solvents make rather complex their conversion to higher value added chemicals. Therefore, innovative processes are now strongly needed in order to increase the selectivity of these reactions. Here, we report an overview of the different heterogeneously-catalyzed processes described in the literature. In particular, hydrolysis, dehydration, oxidation, esterification, and etherification of carbohydrates are presented. We shall discuss the main structural parameters that need to be controlled and that permit the conversion of carbohydrates to bioproducts with good selectivity. The conversion of monosaccharides and disaccharides over solid catalysts, as well as recent advances in the heterogeneously-catalyzed conversion of cellulose, will be presented. 

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