“Breaking” Chemical Bonds to Simplify Organic Chemistry
In Organic Chemistry Simplified Part 1, we talked about how to figure out the number of bonds to each atom. Now, let’s look at some chemical bonds and see what they’re made of…
Chemical bonds are simply 2 electrons
Any bond that we look at can be thought of in terms of two electrons (dots). When we break a bond apart, we can either leave an electron on each atom (homolytic)
or move both electrons to one of the atoms (heterolytic).
This is not how you will typically see this. Therefore, let’s rewrite it as the following:
Keeping an electron on each atom yields two neutral molecules. Placing both electrons on a one atom leaves two oppositely charged molecules.
In your class, you will mainly be dealing with a positively or partially positively charged molecule (electrophile) and a negatively or partially negatively charged molecule (nucleophile). And it is this nucleophile and electrophile pair that is key to every reaction you will learn.
Let’s apply this “breaking bonds” to the functional groups you are learning.
Functional groups and Breaking Lines
Functional groups are what allow you to “do something” in organic chemistry. And the group will either be your nucleophile or your electrophile. This is what they look like when we break them apart:
C-C Single Bond
C=C Double Bond
C=O double bond
C-Halogen Single bond
With carbon-carbon bonds (double and single), the positive and negative charges can be on either atom. Both atoms are obviously carbon; therefore there is no real difference in electronegativity.
However, this is not always the case. If you have a difference in how the carbon is substituted, you always place the positive charge (carbocation) on the more substituted atom.
When you have bonds that contain atoms more electronegative that carbon (essentially everything other than hydrogen), the negative charge will always go with the non-carbon atom. You can see this with the C=O double bond and C-Cl Single bond
So…how will this help you with organic chemistry?
Since every reaction essentially involves a nucleophile and an electrophile, this will help you identify what is attacking (nucleophile) and what is being attacked (electrophile).
In the next section (Organic Chemistry Simplified Part 3), I will show you how to apply this in general way.