Physical properties of monosaccharides

There is a great variety in structure as well as chemical and physical properties of monosaccharides. There is no single method that is applicable to the qualitative and quantitative analysis of all monosaccharides instead, the method must be chosen according to the chemical and physical characteristics of the solutes of interest. Borate complexes of monosaccharides can be separated using strong (quaternary amine, Q-type) anion-exchange columns. Alternatively, if the monosaccharide is acidic... 

In this article, the authors have endeavored to summarize the methods of synthesis and the proofs of constitution of all the known methyl ethers of D-glucopyranose and D-glucofuranose. Acyclic glucose ethers are not considered in this review. Later articles will deal with monosaccharides other than glucose. It has not been possible to discuss in full all the reactions involved, but to offset this disadvantage the bibliography has been made as complete as possible and tables have been compiled of the physical properties of the methyl-D-glucoses and of their more important derivatives. 

The physical properties and many chemical properties of monosaccharides depend on the molecular shape. Equilibria of pyranoid compounds depend largely upon the axial-equatorial relationship between substituents on the rings. Thus, the alp ratio of pyranoses is governed to some extent by the tendency of the anomeric hydroxyl group to occupy the less hindered equatorial substituent orientation. 

During the past ten years, the l,6-anhydro-/3-D-hexopyranoses have found wide application in the synthesis of hexoses and their derivatives, and of oligosaccharides, and for polymerization to polysaccharides. They can be used as model compounds in studying the physical and chemical properties of monosaccharides, as has been shown, for example, by nuclear magnetic resonance (n.m.r.) studies, and also by studies of (a) their chiroptical properties, (b) the partial reactivity of hydroxyl groups, and (c) their ability to form complexes. 

Recently, much attention has been given to the production of liquid sweeteners as an alternative to cane sugar using inexpensive starch-containing natural materials as the primary feed stock. This situation exists in the United States as this country is not self sufficient in the production of cane, but must rely heavily on importation mainly from South America and the Caribbean. The main source of sta rch in the United States comes from corn (Zea mays) and the liquid sweetener commercially produced from this material is called high fructose corn syrup (HFCS). The current method of production of HFCS is via wet milling which exploits the physical properties of the whole corn constituents (oil, starch, gluten, and fiber) for their separation coupled with enzymatic hydrolysis of the starch fraction to monosaccharides. 

Two monosaccharides may be combined with the loss of one molecule of water to form a disacchaiide. Polysaccharides and other complex carbohydrates are then produced by the condensation of more monosaccharide subunits with the loss of a molecule of water for each additional monosaccharide. Depending upon its constitution, hydrolysis of a polysaccharide yields either a single monosaccharide or a mixture of monosaccharides. In this chapter, some of the fundamental chemical and physical properties of carbohydrates will be investigated using simple mono-and disaccharides several classic qualitative tests to characterize and classify carbohydrates will also be performed. 

An understanding of the carbohydrate functionality requires an understanding of the structure, chemical, and physical properties of carbohydrates. Carbohydrates in food comprise anything from a simple carbohydrate (simple sugar or monosaccharide) to highly complex carbohydrates (polysaccharides). Because each of these carbohydrates has certain properties, the structural diversity found in food carbohydrates offer different functional properties. The functional properties are generally derived from the carbohydrate content and are directly related to the carbohydrate structure. Let us take a look at the various carbohydrates found in food. 

The change brought about by dietary fibre in faecal bulk illustrates several things about fibre. Perhaps the most important is that not all types of dietary fibre are the same. Each fibre source is unique in its botanical structure, its physical properties, its monosaccharide composition so far as they have been tested, each is unique in its ability to affect human physiology. It is clearly most unwise to extrapolate from the effects of one type of fibre to the likely effects of another. 

Fischer projections are however, unsatisfactory when considering the physical properties and chemical reactivity of monosaccharides for which definitive spatial formulations are necessary. These are given below for D-glyceraldehyde, D-erythrose and D-threose, for which the (/ ,S configuration may be readily assigned at the appropriate chiral carbons. 

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