Isomers – Epimers | MCAT Organic Chemistry Prep
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Need help preparing for the Organic Chemistry section of the MCAT? MedSchoolCoach expert, Ken Tao, will teach everything you need to know about epimers for isomers. Watch this video to get all the MCAT study tips you need to do well on this section of the exam!
Epimers are a subtype of diastereomer, a case in which a set of diastereomers differs at only a single chiral center. D-glucose and D-galactose are a pair of epimers well worth being aware of for the MCAT.
Both the Fischer and Haworth projections have been provided for both structures. Notice how the two molecules are identical at all except one chiral center, namely the one on carbon 4. This is the only criterion necessary to be deemed an epimer rather than simply a diastereomer.
Anomers are a special subtype of epimers. Two anomers of a single compound differ only at a single chiral center, and logically, must therefore belong to the category of epimers. More on anomers can be found in our sections on the structure of carbohydrates.
Observe how again all chiral centers are in the same absolute configuration, except for a single one. In this instance that is carbon #1, the anomeric carbon of all aldoses. As a useful reminder: In a standard projection, down-facing anomeric hydroxyl groups indicate the α-anomer and up-facing ones indicate the β-anomer. If structures are presented in non-standard orientation, comparison between the absolute configuration of the anomeric carbon and the final carbon of the ring structure is necessary. If the two match in absolute configuration, the α-anomer is present. If the two are opposite, the β-anomer is present.
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Epimers are a subtype of diastereomer, a case in which a set of diastereomers differs at only a single chiral center. D-glucose and D-galactose are a pair of epimers well worth being aware of for the MCAT.
Both the Fischer and Haworth projections have been provided for both structures. Notice how the two molecules are identical at all except one chiral center, namely the one on carbon 4. This is the only criterion necessary to be deemed an epimer rather than simply a diastereomer.
Anomers are a special subtype of epimers. Two anomers of a single compound differ only at a single chiral center, and logically, must therefore belong to the category of epimers. More on anomers can be found in our sections on the structure of carbohydrates.
Observe how again all chiral centers are in the same absolute configuration, except for a single one. In this instance that is carbon #1, the anomeric carbon of all aldoses. As a useful reminder: In a standard projection, down-facing anomeric hydroxyl groups indicate the α-anomer and up-facing ones indicate the β-anomer. If structures are presented in non-standard orientation, comparison between the absolute configuration of the anomeric carbon and the final carbon of the ring structure is necessary. If the two match in absolute configuration, the α-anomer is present. If the two are opposite, the β-anomer is present.
MEDSCHOOLCOACH
To watch more MCAT video tutorials like this and have access to study scheduling, progress tracking, flashcard and question bank, download MCAT Prep by MedSchoolCoach
IOS Link: https://play.google.com/store/apps/de...
Apple Link: https://apps.apple.com/us/app/mcat-pr...
#medschoolcoach #MCATprep #MCATstudytools
4 سال پیش
در تاریخ 1399/08/06 منتشر شده
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