Nomenclature

I said that I would post something today, and I am. However, since I’ve been busy with this and that, I don’t have a comic to put up. Since I’m buried in my chem books (and my science post generates a surprising amount of traffic) I decided to do another chem basics post. I’m sorry if I botch some capitalization conventions, this is a quick note.

Today I’ll be talking about nomenclature, the general rules for naming chemicals. There are many, many exceptions and “common names” that have to be more or less memorized case-by-case, so I’ll just be covering the International Union of Pure and Applied Chemistry rules for organics, or IUPAC for short.

I’m sure that everyone has come across one of those incredibly complex chemical names before. However, they’re deceptively simple. Well, relatively simple at least.

Being carbon-based (as you might have heard), organic chemistry revolves around the organization of “functional groups” around carbon chains. These chains form the base of the names as well, based on how many carbons there are.

Starting from one carbon and moving to ten, we have methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane.

For example: propane, the staple of barbecue cooking, has three carbons in a chain. Since carbon can form four bonds, the formula is CH3CH2CH3. The outer carbons have three bonds to hydrogen and one to the center carbon, and the center has two bonds to hydrogens and one to each of the other carbons.

If you have a double bond then a few things change. First off, the “-ane” ending will become and “-ene” instead (“-yne” for triple bonds). If the bond is not present on the first carbon then you must designate which carbon the bond starts on. For example, a chain with five carbons that has the bond on the second (C-C=C-C-C) would be called “2-pentene”. You always count from the side that results with the lowest number; the previous structure wouldn’t be “3-pentene”.

After we have established the backbone, we can start adding functional groups. These are parts that branch off of the main chain, and can be any number of different things. I’ll only cover a few, of course.

A second carbon chain

You can attach a second bunch of carbons to the main chain. These carbons will use the same naming conventions as the base, except instead of ending with an “-ane” it will end with a “-yl”. Example: Methyl group.

A six-chain with a CH3 group (methyl) coming off the chain on the third carbon would therefore be called “3-Methylpentane”.

An oxygen in hydroxyl form

An oxygen can be attached to a carbon in multiple ways, but the easiest one is the hydroxyl group (OH). Attaching a hydroxyl group to a normal chain turns it into an alcohol, easy as that. To designate this, we replace the ending of the chain name with “-ol” to indicate an alcohol.

For example, the supposedly “green” fuel ethanol (which ignores all the resources put into actually growing the crops when calling itself “green”) is an ethane group with a hydroxyl group attached. That’s all there is to it, CH3CH2OH.

A nitrogen group

A nitrogen group attached to a carbon chain is called an “amine”, and can be found with two hydrogens attached.

When this occurs, the carbon keeps its original name and the word “amine” is put before it along with a placement number if necessary. It’s basically the same process as with the carbon group, just instead of the carbon name you have “amine”.

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That’s all I’m going to put up for now; there’s a lot to nomenclature and, well, let’s just say that there’s a reason why textbooks are so thick.

I wanted to do this because I realize that people are turned off from chemicals because of their scary names. IUPAC exists because we needed a common chemical language that could be understood in any country, regardless of normal language. It’s not intended to confuse consumers and hide the truth from you, not at all. It’s just the best that we could come up with. Hell, a large part of it isn’t even English; the E and Z isomer designations are born out of German terms.

What am I saying? I’m not sure I know. Let’s just sum it up and say that “many chemicals aren’t bad for you, they’re just confusing. Don’t believe the nutjobs at the health food store”.