An organic chemistry reaction cheat sheet serves as a compact reference that highlights essential mechanisms, reagents, and conditions. By organizing named reactions, functional group transformations, and common patterns, this tool helps you quickly recall how bonds break and form during problem solving.
Use this structured overview to build intuition for reactivity trends and to streamline your study or workflow sessions. The table below pairs each key reaction type with its core reagent, primary mechanism, and typical conditions for rapid lookup.
| Reaction Category | Key Reagent or Condition | Typical Mechanism | Common Conditions |
|---|---|---|---|
| Electrophilic Addition to Alkenes | HBr, Br2, H2SO4 | Carbocation intermediate, Markovnikov addition | Room temperature, inert solvent |
| Nucleophilic Substitution | NaOH, KCN, SN1 vs SN2 conditions | SN1 (carbocation) or SN2 (concerted) | Polar protic or aprotic solvent, temperature control |
| Elimination Reactions | KOH in ethanol, heat | E1 or E2, Zaitsev orientation | Heat, strong base, aprotic or protic solvent |
| Carbonyl Addition and Condensation | Grignard, NaBH4, LDA | Nucleophilic addition, enolate chemistry | Anhydrous solvent, low temperature then workup |
| Aromatic Substitution | HNO3/H2SO4, FeBr3 | Electrophilic aromatic substitution | Controlled temperature, avoid overreaction |
Electrophilic Addition Mechanisms
Alkene Reactivity Patterns
Electrophilic addition to alkenes often follows Markovnikov orientation, where the hydrogen adds to the less substituted carbon. Common reagents such as HBr, Br2, and acid-catalyzed hydration provide rapid access to alkyl halides and alcohols when conditions are controlled.
Regioselectivity and Stereochemistry
Carbocation rearrangements can shift the site of addition, so always evaluate possible hydride or alkyl shifts. Stereochemistry is influenced by anti addition in halogenation and syn addition in catalytic hydrogenation, which affects the final 3D structure of the product.
Nucleophilic Substitution Strategies
SN1 versus SN2 Pathways
Substrate structure, nucleophile strength, and solvent polarity determine whether you follow an SN1 or SN2 route. Primary substrates favor SN2, while tertiary substrates prone to rearrangement typically proceed via SN1 with a racemic outcome.
Leaving Group and Base Effects
Good leaving groups such as tosylate, mesylate, and halides enable smoother substitution. Strong bases may instead trigger elimination, so balancing base strength, temperature, and solvent helps steer the reaction toward the desired substitution product.
Elimination and Rearrangement Considerations
E1 and E2 Competition
Strong, bulky bases at elevated temperatures favor E2 and can enhance selectivity for the more substituted alkene per Zaitsev’s rule. Weaker bases and carbocation-prone conditions promote E1, where rearrangements may alter the final alkene distribution.
Steric and Substrate Control
Bulky bases and hindered substrates steer elimination toward less substituted alkenes, while heat and solvent polarity influence elimination over substitution. Mapping these factors helps predict product ratios and suppress side reactions.
Carbonyl and Redox Transformations
Grignard and Organometallic Additions
Grignard reagents add to aldehydes, ketones, and esters, enabling stepwise construction of complex alcohol frameworks. Strict exclusion of moisture and careful quenching are essential to prevent quenching of the organometallic reagent or undesired side products.
Selectivity with Reducing Agents
NaBH4 reduces aldehydes and ketones under mild conditions, while LiAlH4 extends reductions to esters and carboxylic acids. Choices in reducing agent, solvent, and temperature determine speed, selectivity, and the ease of downstream workup.
Optimizing Reaction Planning and Execution
Treat your organic chemistry reaction cheat sheet as a dynamic map that you refine as you encounter new substrates and conditions. Regularly cross check reagents, mechanism, and workup procedures to reinforce reliable habits and avoid recurring mistakes.
- Classify each target transformation by reaction type before selecting reagents.
- Check solvent compatibility and temperature limits for sensitive functional groups.
- Monitor reaction progress using TLC or spectroscopy to avoid overreaction.
- Plan workup and purification steps in parallel to minimize side reactions during quenching.
- Document conditions, anomalies, and yields to build a personalized reference library.
FAQ
Reader questions
Which reagent set should I use for converting an alkene to an anti diol?
Use bromine in water or a bromohydrin formation followed by hydrolysis to install an anti diol with predictable regiochemistry and stereochemistry.
How do I minimize rearrangements when performing an SN1 reaction?
Choose substrates with stable carbocations, use mild conditions, and consider alternative pathways such as SN2 where feasible to limit carbocation rearrangements.
What conditions favor elimination over substitution in secondary substrates?
Employ strong, bulky bases at higher temperatures in aprotic solvents to favor E2 elimination and steer the reaction away from substitution products.
Can I directly convert an ester to a primary alcohol using a single reagent?
Apply excess LiAlH4 followed by careful aqueous workup to reduce escyl groups directly to primary alcohols in a single step transformation.