Here is where Organic Chemistry Simplified Comes Together
In the last section (Organic Chemistry Simplified Part 5), we discussed the reaction scheme and how to find what is most important. Now, we will put everything together and see how all this will help us solve organic reaction questions. Let’s look at the following example:
We will first break down the functional group (alkene):
In this case, the charges can be put on either carbon (same electronegative value).
The reagent (HCl) has a hydrogen in the front; therefore it acts as an H+. Now, we just need to put the charges together:
Well, does it ever matter where we put the charges?…..Absolutely!
The following example will demonstrate this:
Now, let’s look at the charges on the carbons and see what is different.
The charge we want to pay attention to is the positive charge. When talking about carbocations, the stability is as follows:
3O > 2O > 1O
Therefore, the structure on the right has the more stable carbocation (3O vs. 2O).
Finally, we match up our charges:
OK, here is our next example involving a carbonyl group:
As we saw before, the carbonyl group only has one charged structure (due to electronegativity values):
Now, we only need to worry about what is above the arrow:
Since we are dealing with a metal atom, the carbon chain will have the negative charge and the metal will have the positive charge. Finally, put the charges together…
…But wait…Where did the hydrogen come from on the oxygen?? This is a common question I get from students. The more accurate reaction scheme would like this:
When you are using a negative charge (base or nucleophile), a proton source needs to be added to get rid of the negative charge. Some professors allow students to leave this step out while others do not. My best advice is to ask your professor what he or she prefers.