MCAT Mnemonics: 5, 10, 15, 20 Rule

Ken Tao is the MedSchoolCoach expert on MCAT, and will discuss the organic functional groups which are what we call the 5, 10, 15, 20 rule. You’ll learn, specifically, about the pKa of Carboxylic Acid, Phenol, Alcohol, and Alpha Hydrogen used in organic chemistry.

Full Transcription

Welcome back to another episode of MCAT Mnemonic Monday. My name is Ken and I’m an expert with MedSchoolCoach. Today we have an organic chemistry mnemonic for you and it’s on the organic acid functional groups and their pKas. It’s what we call the 5, 10, 15, 20 rule. For the MCAT, you need to know the 4 organic acid functional groups. These are the carboxylic acid, phenol, alcohol, and alpha hydrogen from carbonates. What the 5, 10, 15, 20 rule describes is the pKas of these four organic acid functions.

Remember, pKa is inversely proportional to acidity. So that means the lower the pKa, the more acidic the functional group. So the way the world works is that carboxylic acids have a pKa of about 5. Phenols have a pKa of about 10. Alcohols have a pKa of about 15. And alpha hydrogens off of carbon fuels have a pKa of about 20. That’s it for the mnemonic. And it will be very helpful for you on the MCAT exam.