Rules of the Day 320N

1. The anions of terminal alkynes add to aldehydes and ketones to give tetrahedral alkoxide intermediates (can be isolated). These alkoxides are protonated when the chemist opens the flask and adds acid to give alkyne alcohols. Mechanism A. Carbon-carbon bond forming! See the movie by clicking here

2. HCN is in equilibrium with H+ and CN-. CN- reacts with aldehydes and ketones to give a tetrahedral alkoxide intermediate that cannot be isolated becuase it is immediately protonated to give a cyanohydrin product. Mechanism A. Carbon-carbon bond forming! Time Capsule: Cyanohydrins are hydrolyzed in strong H3O+ to give alpha-hydroxy carboxylic acids. See the movie by clicking here

3. Wittig reactions form C=C bonds from C=O bonds through reaction of the nucleophilic ylide via the famous four-membered ring intermediate (See Pictures of the Day). This is a useful reaction because carbonyl compounds are easily made, and the ylides are made from haloalkanes, also easy to make. Unique mechanism! (See Pictures of the Day) Carbon-carbon bond forming!

4. Alkyl Wittig reagents give predominantly "Z" (cis) alkene products, while Wittig reagents with a carbonyl adjacent to the negative charge give predominantly "E" (trans) products.

Homework:

Read: Sections 16.7, 16.8 in the ebook textbook. This text is part of the Longhorn Textbook access program.

Take the Daily Quiz 4 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture. Together, they will count as 3% of your final grade.

Continue working on the Homework Problem Set 2, due at 10 PM on Monday, Juanuary 29. Click here to access the Homework Problem Set 2. Note there are Aktiv Learning and Gradescope Questions, and you MUST DO BOTH. Homeworks will be worth 10% of your final grade (20% from the Aktiv Learning and 80% from the Gradescope portions of the homework.

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