Diacid Nomenclature: Study with Video Lessons, Practice Problems & Examples

Diacids contain two carboxylic acid groups in the same chain. The simplest diacids are oxalic acid, malonic acid, and succinic acid, which can be remembered with the phrase "Oh my science" (O, M, S). Malonic acid is particularly significant in various reactions, while oxalic acid is less frequently encountered. Understanding these compounds is essential for grasping their applications in organic synthesis and biochemical processes.

Nomenclature of Diacids

I quickly just want to touch on the diacids. Anytime you have 2 carboxylic acids on the same chain, it's called a diacid. You might want to know the first three most simple diacids. The first one is called oxalic acid. The second one's called malonic acid. And the last one is succinic acid. These will have varying levels of relevance this semester. Malonic acid is huge. You're going to hear that a lot. Oxalic, not so much. Succinic comes up a little bit. The biggest thing is just these might come up so you should know at least the 3 most simple ones. If you'll notice, they start off with the letters O, M, S. I was trying to think of a way that you could remember them and then that took me back to that South Park episode where Cartman goes like 500 years in the future and it's a bunch of atheists. And instead of saying, oh my God, they say, 'oh my science' because they're like, you know, so godless. And I think that's perfect. So now you guys memorized it. That's not leaving your head, right? Oh my science, Oxalic, melonic, succinic. All right? Perfect. Let's move on to the next topic.

Provide the common name for the following compound. 

• A. oxalic acid
• B. pimelic acid
• C. succinic acid
• D. adipic acid

Provide the IUPAC name for the following compound. 

• A. 4-oxooctanedioic acid
• B. 5-oxooctanedioic acid
• C. 4-oxooctanoic anhydride
• D. 5-octanone anhydride

Here’s what students ask on this topic:

What are the simplest diacids and how can I remember them?

The simplest diacids are oxalic acid, malonic acid, and succinic acid. You can remember them using the mnemonic 'Oh my science,' which corresponds to the initials O, M, and S. Oxalic acid is the simplest, followed by malonic acid, and then succinic acid. This mnemonic is particularly useful because it helps you recall the order and names of these diacids quickly.

Why is malonic acid significant in organic chemistry?

Malonic acid is significant in organic chemistry due to its role in various reactions, particularly in malonic ester synthesis. This reaction is crucial for forming carbon-carbon bonds, which is a fundamental aspect of organic synthesis. Malonic acid's reactivity and ability to form stable intermediates make it a valuable compound in the synthesis of complex molecules.

How do the structures of oxalic acid, malonic acid, and succinic acid differ?

Oxalic acid (C₂H₂O₄) has two carboxylic acid groups directly attached to each other. Malonic acid (C₃H₄O₄) has a methylene group (-CH₂-) between the two carboxylic acid groups. Succinic acid (C₄H₆O₄) has two methylene groups (-CH₂-CH₂-) between the carboxylic acid groups. These structural differences influence their chemical properties and reactivity.

What are some common applications of diacids in biochemical processes?

Diacids play significant roles in biochemical processes. For example, oxalic acid is involved in the metabolism of certain plants and can form complexes with metal ions. Malonic acid is a key intermediate in the biosynthesis of fatty acids. Succinic acid is part of the citric acid cycle (Krebs cycle), which is essential for cellular respiration and energy production in living organisms.

How can I differentiate between oxalic acid, malonic acid, and succinic acid in a lab setting?

In a lab setting, you can differentiate between oxalic acid, malonic acid, and succinic acid using various techniques. Melting point determination can help, as each diacid has a distinct melting point. Infrared (IR) spectroscopy can identify functional groups and structural differences. Nuclear Magnetic Resonance (NMR) spectroscopy can provide detailed information about the molecular structure, helping to distinguish between these diacids based on their unique chemical environments.