March 6, 2022

Spectroscopy, Coca-Cola, and the Center of the Universe: An Overview of Basic Spectroscopy

Recently, a new beverage from Coca-Cola came out that claimed to be "space flavored". This drink, known as Coca-Cola Starlight, made me ponder how the company would manage to make a drink that tastes like something no human has tasted before. Doing some research into the subject at hand, I stumbled upon a random fact that I've never known. According to research, dust clouds at the center of our galaxy have a known flavor: raspberries and rum! This discovery, while not terribly important to the average person, brought up the question of how astrophysicists figured out such a fact.

Coca-Cola Starlight, a new limited-time flavor!

To be able to make this conclusion, the astrophysicists first determined the molecular structure of the dust using waves emitted. This technique, known by the umbrella term of spectroscopy, allowed the researchers to piece together a molecule that correlated to the different waves. While the idea of spectroscopy seems simple at first, it dives deep into the chemistry and physics of molecules. Of the many different types of spectroscopies I've learned, some of the introductory techniques include Mass Spectroscopy, IR Spectroscopy, and C/H-NMR Spectroscopy.

Mass Spectroscopy

The simplest of the techniques I've learned, mass spectroscopy measures the ratio of mass to the charge of molecules present in a sample (m/z). As one may infer from the name, we can use this type of spectroscopy to get an accurate idea of the molecular weight of the sample being tested, which can help us predict the molecular structure of the sample.

Mass Spectra of Mesityl oxide - MSU Chemistry

The output of mass spectroscopy is a mass spectra; this is a type of graph that shows the relative abundance of molecule fragments at a given m/z. The most important takeaways from this graph are the parent peak (the tallest peak on the graph that all other peaks are relative to), and the molecular ion peak. The molecular ion peak is particularly important since it tells us the weight of the entire molecule and is almost present in every mass spectra.

IR Spectroscopy

Of the different methods to be shown, IR spectroscopy has to be my favorite. This is because IR spectroscopy can determine the functional groups present in a molecule. This spectroscopy works by detecting the different vibrational patterns that are unique to different functional groups. Think of this as scanning unique barcodes that every molecule possesses.

IR Spectra of Vanilla - MSU Chemistry

What's outputted is a graph of transmittance at different wavelengths. By looking at this graph, certain patterns can allow us to pick out certain parts of the molecule. The only big downside to this spectroscopy, however, is that the placement of different functional groups may be difficult since we have no idea of the relative position of the different parts, let alone how many of each functional group there is. This is why IR spectroscopy is often paired with mass spectroscopy and NMR spectroscopy; it allows for the researcher to have every clue necessary to put together the puzzle of determining structure.

NMR Spectroscopy

While being far from my favorite spectroscopy, NMR tells us the most information. It can determine the carbon or hydrogen environment in the molecule by analyzing the spin of those atoms under a magnetic field. Measured in intensity given a specific number of parts per million (ppm), NMR conveys the presence of certain environments by how deshielded/shielded something may be in a fashion similar to IR spectroscopy. NMR goes further, however, by allowing us to determine the specific carbon skeleton structure and the more intricate parts of the skeleton (such as the presence of rings compared to a simple hydrocarbon chain).

H-NMR Spectra of Butanol - UCLA Chemistry and Biochemistry

Closing Remarks

Spectroscopy is a vital part of organic chemistry as it becomes the basis of confirming whether you've got your desired molecule. To be completely honest, I didn't like spectroscopy when I first learned it and I still don't completely love it today. However, with enough dedication to mastering the art of reading spectroscopy outputs and piecing together the information, it can almost become second nature. And with this newfound information, you too can confirm the composition of the center of the galaxy and enjoy the refreshing flavors of raspberries and rum!

And for those of you who are wondering (which I doubt is any of y'all), Starlight smells like Smores and tastes like a slightly more toasty Coke. I can confidently say it wasn't worth it. What is worth it, however, was writing this blog post!