Ch_322b_22.07

Ch_322b_22.07 - Some carbohydrates have the ketone function...

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Nomenclature of the Monosaccharides Not all carbohydrates cyclize to six-membered hemiacetal rings. Five-membered rings are also common. The size of the ring is indicated in the root of the name of the carbohydrate. The root for the name is based on the oxygen heterocycles: O pyran O furan A six-membered hemiacetal is a pyranose . A five-membered hemiacetal is a furanose . The full descriptive name of the glucose hemiacetal structure is: ! - D -(+)- gluco pyranose anomer D-family rotatory power glucose six-membered hemiacetal
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Examples The aldopentoses cyclize to five-membered furanoses. The cyclization process may be described using the step-by-step procedure to the Haworth projection formula. CHO OH OH OH CH 2 OH H H H D-(-)-ribose CHO OH OH OH HOCH 2 H H H OH OH O HOCH 2 H H H OH H ! " D-(-)-ribose 1 4 O HOCH 2 1 4 OH H OH HO H H H D-(-)-ribofuranose
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Unformatted text preview: Some carbohydrates have the ketone function (ketose) that is involved in forming cyclic hemiketals. HO OH OH CH 2 OH H H H =O CH 2 OH 1 2 3 4 5 6 D-(-)-fructose a ketohexose HO OH OH HOCH 2 H H H =O CH 2 OH 1 2 5 HO OH O HOCH 2 H H H 1 2 5 OH HOCH 2 D-(-)-fructose hemiketal structure O HOCH 2 1 OH HO HO H H H CH 2 OH 2 5 D-(-)-fructofuranose Quiz 22.07 Draw D-(+)-mannose in its cyclic hemiacetal conformational structure as the !-anomer. Provide the complete descriptive name of this carbohydrate structure. CHO CH 2 OH OH OH HO HO H H H H D-(+)-mannose CHO HOCH 2 OH OH HO HO H H H H HOCH 2 OH HO HO H H H H O HO H !-anomer hemiacetal 1 5 O CH 2 OH HO HO HO OH 1 5-D-(+)-mannopyranose...
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This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.

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Ch_322b_22.07 - Some carbohydrates have the ketone function...

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