First blog of 2023!
Diverging from technology, I’d like to discuss a bit of chemistry today. Having taken Advanced Chem last semester (and not knowing what I can write 750 words about), I figured describing the very convoluted and backward way organic chemists name molecules would be a great thing to do.
Before we start, there are a few prefixes that you need to know:
Here, Meth- means 1, eth- means 2, prop- means 3, so and so forth.
Let’s start with the most basic molecules, Alkanes. These are single bonded Carbon molecules. Not bad!
Here’s an example below:
C’s denote carbons. Now how do we name this molecule?
We simply count up the amount of carbons (here there are 5), find the corresponding prefix from our handy chart (in this case pent-), and simply add the suffix -ane since this is an Alkane molecule (single bonds connecting the carbons, seen above by the single dashes), this molecule is pentane.
That wasn’t bad! But a majority of molecules have branches of either carbon chains (like what we see above), or different elements.
Here is a slightly harder molecule:
I’ll explain the Iodine (I) and bromine (Br) seen here. There are a few molecules that are often attached to these carbon molecules, which we denote with the prefix Iodo- for iodine, bromo- for bromine, fluoro- for fluorine, etc. Since this molecule is more than just a simple chain, we need to order our branches.
We start ordering from the end with the closest branch. Since with this molecule, either end has a Iodo- molecule or a bromo-molecule 1 carbon in, this is a tie and results in us using the very backwards approach organic chemists take to order these molecules: going by the alphabet.
Which letter comes first, I (like iodo-) or B (like bromo)? Bromo, so we start ordering our molecule from that end. So from right to left, we name each carbon with a number, starting with 1, then 2, then 3, then 4, up to 6.
Lastly, we have a carbon branch. Referring to our table, this is a single carbon, so it should start with the prefix Meth-. Since it’s a branch, we end it with -yl, so we call this branch methyl.
Now taking all those parts together, we have our right to left ordered carbon, bromo, iodo, and methyl branches, now it’s time to name! Here’s a picture below, with the carbons ordered and the branches circled.
Again, going by the alphabet, we name the branches before the base molecule, so bromo, iodo, then methyl.
Bromine is attached to the second carbon, so we name this branch as 2-bromo. Iodine is attached to the 5th carbon, so we name it as 5-iodo. (Note here, while the methyl is the next molecule we should name, organic chemists chose to do it alphabetically so we have to name the iodine branch first!). Lastly, we have the methyl branch, attached to the 3rd carbon, so we call it 3-methyl.
Finally, since we have 6 carbons, consulting our handy chart this works out to be hex- as a prefix, so hexane as the base chain of 6 molecules.
Put it all together, and this molecule is 2-bromo 5-iodo 3-methyl hexane.
Nice! We can name linear molecules, but what about circular ones?
Here’s a more complex molecule. Note how the red donut of 5 carbons are connected to each other in a circular fashion. Since they are this way, we add the prefix cyclo- to the ending bit of the molecule. Since this central (red) ring of carbons contains 5 of them, referring to our table this molecule should have pent- in it. Furthermore, we can see the “bonds” or lines around the 4 o’clock region of the molecule are double instead of single, this denotes a double bond, which would mean this molecule is an alkene, slightly different from the Alkanes we named earlier. This means the molecule above would end with the conventions cyclopentene.
Onto ordering the carbons! We found with the previous molecule that we need to order the carbon order so that the branches are in the right places. Since this is a alkene, we must start at a double bond (more organic chemistry backwardness). Yet do we name our carbons clockwise or counterclockwise?
It turns out here that we should follow the red number order, since each way you start naming you name a branch on the 3rd carbon. Since the E in Ethyl comes before the F in fluoro, we name with the red numbers.
All in all, this makes the molecule 3-ethyl 5-flouro 4-iodo cyclopentene.
Here’s Mrs. Brucker’s youtube channel for further information: https://www.youtube.com/watch?v=GJVvOixr–c&list=PLQAytuMyLyMVTdfLoCTSCEsGr6Qb46OMs. She is infinitely better than me at teaching this material!
-Max