Study guides › C/P › Organic Chemistry
Structure, Nomenclature & Isomerism
Organic chemistry starts with reading structures. You will recognize the common functional groups, name compounds by IUPAC rules, count degrees of unsaturation, and use hybridization, resonance, and pKa to judge acidity and basicity.
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What this chapter covers
- Functional Groups. A functional group tells you how a molecule reacts. Recognizing them on sight is the first skill in every organic question.
- IUPAC Nomenclature. The MCAT gives you a structure and asks for a name, or the reverse. A fixed sequence of steps makes it routine.
- Constitutional Isomers & Degrees of Unsaturation. A molecular formula alone can hide many structures. Degrees of unsaturation narrow them down fast.
- Hybridization, Bonding & Resonance. Hybridization sets geometry, bond length, and acidity. Resonance explains why amides are flat and carboxylates are stable.
- Acidity, Basicity & pKa. Deciding which proton comes off, and which way an acid-base reaction runs, is worth points across all of organic chemistry.
Key points to know
- Acid > anhydride > ester > acid halide > amide > nitrile > aldehyde > ketone > alcohol > amine
- Aldehyde C=O has an H; ketone C=O has two carbons
- Longest chain containing the principal group, then lowest locant for that group
- Alphabetize substituents, ignoring di-, tri-, tetra-
- Constitutional isomers differ in connectivity; stereoisomers do not
- DoU = (2C + 2 + N − H − X)/2; ignore O and S
- sp³ = 109.5°, sp² = 120°, sp = 180°
- More s character: shorter bonds and more acidic C–H
Try a practice question
Which structure contains an amide?
- mol:CC(=O)OC
- mol:CC(=O)NC
- mol:CCC#N
- mol:CC(=O)Cl
Show the answer
B. An amide has a carbonyl carbon bonded directly to nitrogen. The first choice is an ester, the third a nitrile, and the fourth an acid chloride.
Common questions
What does this chapter cover?
Structure, Nomenclature & Isomerism covers Functional Groups, IUPAC Nomenclature, Constitutional Isomers & Degrees of Unsaturation, Hybridization, Bonding & Resonance, Acidity, Basicity & pKa.
What should I know first?
Acid > anhydride > ester > acid halide > amide > nitrile > aldehyde > ketone > alcohol > amine Aldehyde C=O has an H; ketone C=O has two carbons Longest chain containing the principal group, then lowest locant for that group
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.