Proton NMR

Just as doctors use this tech to identify issues, scientists use the same principals to identify chemicals. Its good to know the rules and conventions of organic chemistry, but how do researchers even identify the compounds they create? Most the time these chemicals are just odorless, clear liquids anyway. In order to sort through these, researchers use a technique called NMR, meaning nuclear magnetic resonance. Watch this video from crash course to get an understanding of the basic type of this technology, proton NMR. 

There is a a ton of information in that video, so here are some high points:

-NMR stands for nuclear magnetic resonance

-Proton NMR reads where the protons in a molecule are, and plots then on a graph

-A chemical called TMS gives off a very strong and standard signal, so all chemicals are compared to TMS on the graph (x axis is ppm)

-The integral, or area under the curve, identifies how many carbons are at that spot of resonance. Protons at the same carbon are chemically equivalent, and fit into the same peak.

-If a peak is to the right, it is referred to as upfield, it is the most shielded, and furthest from electronegative atoms

-If a peak is to the left, it is referred to as downfield, it is the most deshielded, and closest to electronegative atoms

-Coupling refers to protons effect on one another. This leads to split peaks

-To predict split peaks, use the n+1 rule. N is the number of protons on carbons adjacent to the carbon atom who's hydrogen peak you are looking at. 

-This chart from crash course gives an idea of where common groups fall

Before you start trying practice problems, watch someone identify a molecule through a NMR reading with this video. If you want to get another run down of the concept, watch this video from professor Dave. 

In the video of the practice problem above, the numbers by the peaks (3,2,3) are in reference to the number of hydrogens in that peak. These numbers are proportional to the number of hydrogen atoms in that region of the molecule. There is a way to determine these numbers through some math but that is more in depth than what this course is designed for. For now, all practice problems will have these numbers written next to the peaks, just know that they correspond to the area underneath the peaks. 

Once you feel comfortable with NMR, take this quiz.