If you’re leaving for an O-Chem exam in 3 minutes or less, read this.
My one-sentence advice to those about to write an exam: Number your carbons.
Now go write your exam.
If you need reasons, here they are. There’s two.
First reason: if you number all the carbons in your starting compound(s), it helps you double check that you didn’t miss any in your product. Under the high stress atmosphere of an exam, it’s easy to make little mental mistakes like drawing a 4 carbon chain as a 3 carbon chain and so on. This is a quick protocol that will help to prevent that.
Second reason: When drawing products of a given reaction, numbering all the carbons helps you avoid getting lost. It’s a shame to watch students recognize where all the electron-pushing arrows are supposed to go only to draw their product incorrectly. Figuring out where the electrons are supposed to go is the hard part. Drawing the new product should be a slam dunk. Numbering really helps with this.
2 Quick examples of what I mean:
Note that when I say “number” I don’t mean do it in the “proper”, IUPAC way. I just mean label them in some way that makes each carbon unique so you know where to stitch the pieces together.
Theseus needed a ton of skill to hunt down and defeat the minotaur in the labyrinth. But in the end it was that 99 cent ball of twine that saved his butt by helping him find his way out.
Numbering the carbons is your ball of twine.
Chapter 00 A Primer On Organic Reactions
- Leaving Groups Are Nucleophiles Acting In Reverse
- What Makes A Good Nucleophile?
- Nucleophilicity vs. Basicity
- Nucleophiles and Electrophiles
- 7 Factors That Stabilize Positive Charge in Organic Chemistry
- Curved Arrows (2): Initial Tails and Final Heads
- 7 Factors that stabilize negative charge in organic chemistry
- Common Mistakes: Formal Charges Can Mislead
- The Third Most Important Question to Ask When Learning A New Reaction
- Curved Arrows (for reactions)
Chapter 01 Acid Base Reactions
- Putting Acidity In Perspective
- Acid Base Reactions: What's the Point?
- Acid Base Reactions Are Fast
- A Handy Rule of Thumb for Acid-Base Reactions
- Walkthrough of Acid-Base reactions (4) - pKa
- Walkthrough of Acid-Base Reactions (3) - Acidity Trends
- Walkthrough of Acid Base Reactions (2): Basicity
- Walkthrough of Acid Base Reactions (1)
- Introduction to Acid-Base Reactions
- How to Use a pKa Table
Chapter 02 Alcohols, Epoxides and Ethers
Chapter 03 Aldehydes and Ketones
- Weird Nomenclature In Carbonyl Chemistry
- On Acetals and Hemiacetals
- Imines and Enamines
- Acid Catalysis Of Carbonyl Addition Reactions: Too Much Of A Good Thing?
- Breaking Down Carbonyl Reaction Mechanisms: Reactions of Anionic Nucleophiles (Part 2)
- Breaking Down Carbonyl Reaction Mechanisms: Anionic Nucleophiles (Part 1)
- Carbonyls: 10 key concepts (Part 2)
- Carbonyl Chemistry: 10 Key Concepts (Part 1)
Chapter 04 Alkanes and Nomenclature
- Common Mistakes: Drawing Tetrahedral Carbons
- Don't Be Futyl, Learn The Butyls
- Hidden Hydrogens, Hidden Lone Pairs, Hidden Counterions
- Condensed Formulas: Deciphering What the Brackets Mean
- Table of Functional Group Priorities for Nomenclature
- Summary Sheet - Alkane Nomenclature
- The Many, Many Ways of Drawing Butane
- Meet the (Most Important) Functional Groups
- Common Mistakes in Organic Chemistry: Pentavalent Carbon
- Branching, and Its Affect On Melting and Boiling Points
Chapter 05 Alkene Reactions
- Synthesis (4) - Reactions of Alkenes
- Alkyne Addition Reactions - The "Concerted" Pathway
- Alkyne Addition Reactions: The 3-Membered Ring Pathway
- Summary: Alkene Reaction Pathways
- Alkene Reactions: Ozonolysis
- A Fourth Alkene Addition Pattern - Free Radical Addition
- An Arrow-Pushing Dilemma In Concerted Reactions
- Alkene Addition Pattern #3: The "Concerted" Pathway
- Hydroboration of Alkenes: The Mechanism
- Hydroboration of Alkenes
Chapter 06 Amines
Chapter 07 Aromaticity
Chapter 08 Bonding, Structure, and Resonance
- How to apply electronegativity and resonance to understand reactivity
- Drawing Resonance Structures: 3 Common Mistakes To Avoid
- In Summary: Resonance
- Exploring Resonance: Pi-acceptors
- Exploring Resonance: Pi-Donation
- Evaluating Resonance Forms (4): Positive Charges
- Evaluating Resonance Forms: Factors That Stabilize Negative Charges
- Evaluating Resonance Forms (2): Applying Electronegativity
- Evaluating Resonance Forms (1) - The Rule of Least Charges
- How To Use Curved Arrows To Interchange Resonance Forms
Chapter 9 Carbohydrates
Chapter 10 Carboxylic Acid Derivatives
- Simplifying the reactions of carboxylic acid derivatives (part 1)
- Summary Sheet #7 - 21 Carbonyl Mechanisms on 1 page
- Carbonyl Chemistry: Learn Six Mechanisms For the Price Of One
- Carbonyl chemistry: Anionic versus Neutral Nucleophiles
- Summary Sheet #5 - 9 Key Mechanisms in Carbonyl Chemistry
- How Reactions Are Like Music
- Let's Talk About the [1,2] Elimination
- Proton Transfers Can Be Tricky
- Carbonyl Mechanisms: Neutral Nucleophiles, Part 1
- The Magic Wand of Proton Transfer