Rules of the Day 2-13-08

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

1. Write an original poem on a card you make, then take your sweety to a nice dinner. That beats flowers or candy everytime!!!

2. Cyclic acetals are good protecting groups for use with Grignard reagents, since the cyclic acetals can be reversibly attached, and they have an sp3 carbon atom that won't react with nucleophiles like carbonyls do.

3. Imines are formed when a primary amine or ammonia reacts with an aldehyde or ketone with some acid around. The mechanism involves mechanism C to make a aminal, followed by protonation of the OH group then loss of water at the same time a proton is lost from the nitrogen atom. Like acetal formation, this process is reversible and can be run in either direction depending on the ratio of amine (ammonia) to water in the solution.

4. Imines can be reduced as they are made to give amines if H2/Pd is added to the reaction.

5. Aldehydes are easily oxidized to carboxylic acids using H2CrO4 in H2O.

6. Aldehydes and ketones can be reduced by H2/Pd to give alcohols. (Watch for racemic mixtures!) Note that this method will also reduce any carbon-carbon double or triple bonds that happen to be in the molecule.

7. Metal hydride reagents can be used to reduce aldehydes and ketones to alcohols, but in this case carbon-carbon double or triple bonds are NOT reduced. In these reagents, NaBH4 (less reactive) and LiAlH4 (more reactive), the hydrogen atom is the nucleophile, that attacks a carbonyl carbon atom to give a tetrahedral intermediate, followed by addition of water to the reaction flask that protonates the oxyanion to give the alcohol product. Mechanism A.

Homework: Start working on a practice homework problem set that is meant as a helpful recview. You will NOT turn it in. Click here to download the pdf.

Read: 16.10-16.12 Problems: 16.11-16.13, 16.43, 16.46, 16.51