Open-chain form of glucose

We should first consider the open-chain form of glucose 6-phosphate, rather than its pyranose hemiacetal form (see Section 12.2.1). The open-chain aldose has the requirements for enolization, namely a hydrogen a to the aldehyde carbonyl group. Enolization produces in this case an enediol, which can revert to a keto form in two ways, i.e. reforming... 

Order the following substances from the least to most oxidized carbon Formaldehyde, carbon dioxide, methane, formic acid, methanol. Use the open-chain form of glucose and the structural formula for decanoic acid and this scheme to determine the aver-... 

Although the open-chain form of glucose has four chiral centers, formation of the ring creates a fifth chiral center, which is, of course, why there are two anomers that differ in optical rotation. When solid a-D-glucose is dissolved in water, [a]o is +112°. When solid /3-D-glucose is dissolved in water, [c ]d is +19°. 

Question How do we translate the open-chain form of glucose into five-membered Haworth projection formulas and assign the symbols a and p to the appropriate formula ... 

In the cyclization of the open-chain form of glucose to form the stable hemiacetal, it may be difficult to work out what has happened. Number the carbon atoms in the open-chain form and put the same numbers on the hemiacetal so that you can see where each carbon atom has gone. Then draw a mechanism for the reaction, glucose open-chain form cyclic form... 

The open-chain form of glucose is in equilibrium with both pyranose and furanose forms by hemiacetal formation with the black and green OH groups, respectively. Normally, the pyranose form is preferred, but the furanose form can form a double acetal with acetone, one acetal having as-fused 5/5 rings and the other being on the side chain. This is the product. 

For an aldohexose such as glucose, the C-1 aldehyde in the open-chain form of glucose reacts with the C-5 hydroxyl group to form an intramolecular hemiacetal. The resulting cyclic hemiacetal, a six-membered ring, is called pyranose because of its similarity to pyran (Figure 11.4). Similarly, a ketone can react with an alcohol to form a hemiketal. 

Figure 11.4 Pyranose formation. The open-chain form of glucose cydizes when the C-5 hydroxyl group attacks the oxygen atom of the C-1 aldehyde group to form an intramolecular hemiacetal. Two anomeric forms, designated a and (i, can result.

How man/ chiral carbon auoms aie there in the open-chain form of glucose (Figure 24.21) SOLUTION... 

The open-chain form of glucose constitutes only a small fraction of any glucose sample. Yet, when Cu is used to oxidize the open-chain form, nearly all the glucose in a sample reacts. Use Le Chatelier s principle to explain this observation. 

FIGURE 1. Protein glycation. The open chain form of glucose can react with protein reversibly, forming a Schiff base. This may then rearrange to form the Amadori product, which in turn can form advanced glycation end products (AGE). The formation of AGE, attached or unattached to protein, occurs in a transition metal-dependent oxidative process. This process has also been termed glycoxidation. 

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