Rules of the Day 2-6-08

Click here for a copy of the mechanism sheet used in lecture today.

1. Grignard reagents 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 alcohols. Mechanism A. Carbon-carbon bond forming!

2. Aldehydes and Ketones connect to your 310M and roadmaps through alkenes (ozonolysis breaks C=C bond!) and oxidation of primary (PCC gives aldehydes) and secondary (PCC or H2CrO4 gives ketones) alcohols.

3. With some aldehydes and ketones (those without alpha hydrogens [stay tuned to find out what this means]), alkyl lithium reagents react like Grignards. Mechanism A. Carbon-carbon bond forming! However, for this class, you are better off using Grignards for reactions with aldehydes and ketones and alkyl lithium reagents as very strong bases.

4. 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!

5. 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 a-hydroxy carboxylic acids.

Homework: Start working on the fourth homework problem set, due Wed, 2-13-08, BEFORE CLASS. Click here to download the pdf.

Read: Sections 16.7, 16.8 Problems: 16.6-16.8, 16.15, 16.29, 16.30, 16.32, 16.33, 16.38 in the book. You will not turn these in but they are very helpful to PREPARE for the next lecture.