Why Some Sugars Have a Cyclic and a Chain Structure

Chemistry, Education
In your current course of organic chemistry, you're studying sugars. You notice in a text or see on the web a particular sugar, you've searched for by name. What is its true structure? You see it drawn as a chain structure with pendant groups. As you read about it, you see reference to another structure... a cyclic structure! What gives? Sugars: Example Fructose Some chemicals undergo change with the most minimal modification of environment. One example is keto-enol tautomerism. Fructose and certain other sugars experience something similar. It reacts reversibly, to form two cyclic hemiketals. Fructose Hemiketals A hemiketal forms by combination of an alcohol group with a ketone group. Fructose supplies both reactive groups, internally. For the generic reaction for hemiketal formation, see the accompanying illustration. Note the presence…
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Mono- Di- and Polysaccharides: Starches Sugars Cellulose

Biology, Chemistry
[caption id="attachment_24172" align="alignright" width="480"] This Giant Sequoia stands tall thanks to Cellulose. – Image by Tripastute[/caption] Carbon appears to be unique in its immense chemical diversity. So much so, that an entire branch is devoted to its chemical behavior – organic chemistry. Yet, the name given to this branch of chemistry indicates something of more importance than its being just another branch among many. Organic chemistry began as the chemistry of living things, the chemistry of all things organic. There are literally millions of carbon compounds incorporated into organic chemistry. The group we will consider here is the saccharides. Some among these consist of multiple saccharide units joined together. Hence, they are termed polysaccharides. What is a Saccharide? The word “saccharide” is derived from the Latin sacchararum, “meaning full of…
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