Integrated SequencePhysics Chemistry Organic Biology

Web Resources

Virtual Textbook of Organic Chemistry - Hydration and Hemiacetal Formation

Virtual Textbook of Organic Chemistry - Acetal Formation

Purdue University - Nucleophilic Attack by an Alcohol
Good coverage of the mechanism with some nice supplementary discussion of the importance of hemiacetal and acetal formation in biochemistry.



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Special points of emphasis

Chemical Kinetics

Organic Acids and Bases

Reactions of Aldehydes and Ketones

Acid catalysis occurs twice in acetal formation. First, the carbonyl group is activated for nucleophilic attack by protonation, and, later, the hydroxyl group of the tetrahedral intermediate is protonated, making it a better leaving group.

This is the kind of little fact that isn't so much in itself, but is really helpful for remembering the mechanism. The more networked your knoledge is with associations, the more you will retain the fundamentals.




Reactions of Aldehydes and Ketones

Carbohydrates

Nucleic Acids

Hemiacetal formation is the mechanism by which pentoses and hexoses assume their cyclic forms. Nucleophilic attack by typically the #4 or #5 carbon's hydroxyl group onto the carbonyl group (the anomeric carbon) of the noncyclic form leads to hemiacetal formation. Another nucleophile can act out the second part of the acetal formation mechanism upon the anomeric carbon forming a mixed acetal, termed a glycoside. The nucleophile may be adenine, guanine, cytosine, thymine, or uracil, in which case the glycoside product is a nucleoside, a fundamental building block of the nucleic acids DNA and RNA. If the nucleophile is another sugar, the process leads to the formation of a disaccharide (or polysaccharide). In other words, disaccharides are glycosides with the nucleophile being another sugar molecule.







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