Rules of the Day

1. When doing synthesis problems (enhanced edition):

A) You must have your entire roadmap learned so you can recite the NIRRS parameters for each reagent, i.e. Nature of overall transformation ("locations" on the roadmap), the Intermediate or transition state (carbocation, anti-periplanar etc.), the Reagents and how to designate them, as well as any Regiochemistry (Markovnikov, etc.) and any appropriate Stereochemistry (syn, anti, InVERSiON, scrambled, etc).

B) Work backwards (learn to RECOGNIZE the appropriate reagents and starting materials by looking at the products) from the final product. DO NOT try to work forward from the starting materials. Please trust me on this.

C) Count carbons in the starting material(s) and product(s) to see if any carbon-carbon bonds need to be broken or made, thereby zeroing in on key steps. This will be far more important next semester, so you should get used to doing this now.

D) Pretty much all synthesis problems in OChem 1 involve traveling "north or south" on the so-called "I-35" reactions (alkanes SA, haloalkanes NB/SM, alkenes ATX, vicinal dihaloalkanes Waco, alkynes DFW) at least part way at some point during the synthesis. This is not a promise or a rule, just an observation.

3. The general rule of solvation is "like dissovles like", so polar, hydrogen bonding solvents dissolve polar, charged, or hydrogen bonding molecules and non-polar hydrocarbons dissolve nonpolar hydrocarbons. Non-polar material does not dissolve in polar solvents because the polar molecules stick to each other too well.

4. Alcohols are realtively weak acids with pKa's in the 15-19 range. Thiols are more acidic, with pKa's in the 8-12 range since the larger S atom can more easily accomodate the negative charge.

5. Alcohols react with Na° metal to form H2 and alkoxides, which are interesting because they are strong nucleophiles and strong bases.

6. 3° and 1° alcohols react with H-X to give haloalkanes via protonation followed by SN1 and SN2 mechanisms, respectively. 2° alcohols give too much rearrangement to be useful. Note the stereochemistry is scrambled for the 3° alcohols (SN1).

7. Alcohols react (dehydrate) with strong acid to give alkenes. 2° and 3° alcohols react via a combination of protonation and an E1 mechanism (carbocation rearrangements possible!) and 1° alcohols react via a combination of protonation and E2. In both cases, remember to make the Zaitzev product when there is a choice.

8. Alcohol dehydration is just the functional reverse of acid-catalyzed alkene hydration. The process is actually an equilibrium, the position of which depends on the reaction conditions.

9. 1° and 2° alcohols react with PBr3 and SOCl2 to give bromo alkanes and chloroalkanes, respectively, via a mechanism involving SN2 attack and thus InVERSiON of stereochemistry. The reagent SOCl2, reacts with alcohols to give chloroalkanes in a mechanism analogous to PBr3.