Acetic acid ball and stick

Acetic acid.

The acid-base behavior of various organic substances is an important theme. In many cases, the acidity or basicity of a certain species is an important factor in its reactivity. The slight acidity of primary alkynes, for example, enables their employment as nucleophiles in certain reactions of importance in organic synthesis. Furthermore, the acidity or basicity or certain functional groups, especially the acidity of the carboxyl group and the basicity of the amine group, are crucially important in biochemistry.

Beyond the acidity of the carboxyl group and basicity of the amine group, which are obviously important for the exam, the MCAT will also probe after the specific detailed knowledge in the reaction chemistry, because it is a good index of overall student mastery of organic chemistry. The MCAT likes to see if you know of the special acidity of phenol or if you understand the behavior of the acidic α-proton in keto-enol tautomerism. You will also sometimes see questions regarding substituent effects on acidity or basicity. Being able to judge the effect of a near substituent on acidity or basicity is a good indicator of the overall conceptual ground beneath your organic chemistry understanding.

WikiPremed Resources

Formation and Use of Acetylide Anion Nucleophiles
Mechanisms and explanations from the Organic Mechanisms Pocketbook

Alkoxide Ion Formation from Alcohols
Mechanisms and explanations from the Organic Mechanisms Pocketbook

Acid or Base Catalyzed Enolization
Mechanisms and explanations from the Organic Mechanisms Pocketbook

Saponification of Esters
Mechanisms and explanations from the Organic Mechanisms Pocketbook

Organic Acids and Bases Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Organic Acids & Bases
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Be able to name the organic acids and compare their relative acidities.

Understand how basicity varies for amines depending on whether the amine is primary, secondary or tertiary.

Be able to correctly predict substituent effects on the acidity of carboxylic acids.

Given the pKa of a carboxylic acid or ammonium cation, be able to predict the most common state of ionization within a sample at varying values of pH.

Have a clear sense of the acidity and basicity of alcohols and phenols.

Suggested Assignments

Review the basic terms for organic acids & bases using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Review the web resources for organic acids & bases.

Conceptual Vocabulary for Organic Acids & Bases

Acetic acid
Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell.
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of a carboxyl group.
Organic base
Amines and nitrogen-containing heterocyclic compounds are organic bases.
Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. Structurally amines resemble ammonia, wherein one or more hydrogen atoms are replaced by alkyl and aryl groups.
An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom.
An acetate, or ethanoate, is a salt or ester of acetic acid.
Phenol, also known under an older name of carbolic acid, possesses a structure consisting of a hydroxyl group bonded to a phenyl ring.
Benzoic acid
Benzoic acid is a colorless crystalline solid and the simplest aromatic carboxylic acid.
Nitrogenous base
Nitrogenous bases are organic compounds that owe their basic properties to the lone pair of electrons of a nitrogen atom.
Enols are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond.
Formic acid
Formic acid (systematically called methanoic acid) is the simplest carboxylic acid
Malonic acid
Malonic acid is a dicarboxylic acid with two carboxyl groups bound to a central carbon.
Advanced terms that may appear in context in MCAT passages
Basic aromatic ring
Basic aromatic rings are aromatic rings in which the lone pair of electrons of a ring-nitrogen atom is not part of the aromatic system and extends in the plane of the ring.
Methylamine is a derivative of ammonia, wherein one H atom is replaced by a methyl group
Harpoon base
A harpoon base is an organic base that is a very strong base but at the same time a poor nucleophile.