Mutarotation maltose

The two stereoisomeric forms of maltose just mentioned indergo mutarotation when dissolved in water What is the structure of the key intermediate in this process ... 

Maltose, l- 4- -link in, 998 molecular model of, 998 mutarotation of, 998 structure of, 998 Manicone, synthesis of. 805 Mannich reaction. 915 Mannose, biosynthesis of, 1011 chair conformation of, 126 configuration of, 982 molecular model of, 126 Margarine, manufacture of, 1063 Markovnikov. Vladimir Vassilyevich. 192... 

In polarimetric determinations, the mutarotation must always be taken into account, this being greatest in glucose and less marked in levulose, invert sugar, maltose and lactose. Solutions of these sugars do not assume constant rotations until they have been prepared about 24 hours or kept at a high temperature for a short time. 

Carbon-1 of the second (right hand) glucose unit in maltose is a hemiacetal carbon. Thus, the a and p forms at this carbon atom can equilibrate via the open-chain aldehyde form. Mutarotation is, therefore, possible. Note that carbon-1 of the first (left-hand) glucose unit is an acetal carbon. Its configuration is, therefore, fixed (as... 

Like cellobiose, maltose has a free hemiacetal ring (on the right). This hemiacetal is in equilibrium with its open-chain form, and it mutarotates and can exist in either the a or jS anomeric form. Because maltose exists in equilibrium with an open-chain aldehyde, it reduces Tollens reagent, and maltose is a reducing sugar. 

Draw the structures of the individual mutarotating a and (i anomers of maltose. 

Yes. Although it is a glycoside, the second glucose unit possesses an anomeric carbon atom and its ring can open to give an aldehyde. For the same reason, solutions of maltose display mutarotation. 

Maltose is 4-a-D-glucopyranosyl-p-D-glucopyranose. It is the major end product of the enzymic degradation of starch and glycogen by p-amylase and has a characteristic flavor of malt. Maltose is a reducing disaccharide, shows mutarotation, is fermentable, and is easily soluble in water. 

Maltodextrins a-amylase action on, 315 from amylose, 318,321,323 salivary a-amylase action on, 319 Maltose, /3-, mutarotation of, 23 —, l,2,2, 3,3, 4 -hexa-0-acetyl-6,6 -di-0-p-tolylsulfonyl-/3-, 241 Maltoside, methyl 6,6 -di-0-p-tolylsulfo-nyl-/3-, 241 Mannans... 

Like maltose, lactose also contains a hemiacetal, so it exists as a mixture of a and P anomers. The P anomer is drawn. Lactose undergoes mutarotation, and it reacts with oxidizing agents, making it a reducing sugar. 

Before mutarotation After mutarotation D-Glucose, % Maltose + maltotriose, %... 

Maltose a-D-glucose + a-D-glucose a(1 -+4) Germinating cereal and malt Forms osazone with phenylhydrazme. Fermentable by enzyme maltase present in yeast. Hydrolysed to two molecules of D-glucose. Undergoes mutarotation. 

Maltose behaves as a normal reducing sugar, showing mutarotation and existing finally in aqueous solution as an equilibrated mixture of the a-form and the S-form Modern ideas about connections between optical rotation and structure are reported in the literature [105]. 

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