Practice Exam

Dec 11 and Dec 12 2008 Final Review - Exam is tomorrow

How to make

The following three things are major starting materials that can attacks halide that yield a much longer chain. So in case you have to think for multi synthesis, for the nucleophile ( the attacker) these three should be always in mind.

So who will be attacked? The following 4 can be attacked.

The first two are ketone aldeyhde.

The last two are ester and acyl chloride.

How to make two repeat groups on a multi-synthesis? Always starts from acyl chloride or ester.

1. Why Bromoration is more selective than chlororation?   The transition states in bromoration is more resemble to the product whereas chlororation’s transitional states is more close to the reactants.

2. In E2, if the nucleophile is bulky, the product favors Hoffman. Hoffman product is the alkene that has least substitutes.

3. I-   = it is a weak base, strong nucleophile and good leaving group

4. Comparison on most stable major product on the 2 resonance structures – When you determine what is the most stable resonance structure at the first structure and second structure.  

     Rule 1: octet rule has to go first. Rule 2: the negative charge should be placed on most electronegative atom. Rule 3: A neutral molecule is better than a charge molecule. The trick is that – one may have positive charge on oxygen and another resonance structure has positive charge on carbon. What do you usually do? You would pick the carbon as the major product because we thought that the carbon is the least electronegative. But in this case, we have to look at the octet rules first!! Does oxygen has 8 electrons when it is positive charge? Yes. How about the carbon that has a positive charge? No! The first rule now will go before the second rule. That is why we will pick the oxygen positive in this questions as a major product even thought initially it looks like the positive charge should place on carbon.  

1. aLkyne + SiaB… -> anti-mark. It makes aldeyhde   ( Double O bond on the carbon that is bonds to hydrogen.

2. Alkyne + HgSO4, H2SO4, H2O -> markovnikov. It makes ketons.  ( the carbon bonds to the carbon that has more substitutes.

3. KMnO4 in cold OH- for alkene. It makes diols ( glycols) – two OH group.

4. KMnO4 in warm condition – It makes alkene cleavage.  Review the cleavage. http://www.yourformulasheet.com/Alkene-Reaction.htm.  Make sure if you see aldehyde when alkene reacts with KMnO4, it has to go to carboxylic acid. If OsO4 is used, it stops at aldeyhde. 

Exam review for FINAL - Dec 9, 2008.

1. Naming – please look this example. http://www.yourformulasheet.com/organic-chemistry-nomenclature.htm ( If you have the same substitution at the same lowest number, you go by this rules)

2. How to make a internal alkyne from terminal alkyne? KOH at 200 degree. The triple bond in the terminal alkyne will switch over next to it.

3. NaNH2 can chop off two ends of C2H2 ( the simple alkyne) – this is for the multi-synthesis. Very useful on the questions. In other words, if you see the beginning the materials is C2H2, and the products is some kind of internal alkyne, you know you form a acetylide ion ( C triple bond C minus sign) on the two ends and mostly likely attacks C=O group and other groups to enlogate the structure.

4. PCC can make primary alcohol to aldehyde and it can also make the secondary alcohol to ketone.

5. Compounds that has two asymmetric carbon but achiral compound – that is meso compound

6. Compound that has no chiral carbon but chiral compound – certain alkene can do the tricks.

7. What can make a primary alcohol in the synthesis? Something attacks  epoxide.

8. How to make an epoxide? Alkene plus  MCPBA or CH3COOOH. ( peroxylic acid) However, if you have alkene add MCPBA +H3O, that will give you anti-hydroxylation – two OH on different sides of alkene  http://www.yourformulasheet.com/Alkene-Reaction.htm  (scroll all the way down)

9. Solvent: if “heat” is seen, it is SN1 or E1. ( they helps ions flowing)