MCAT Organic Chemistry Mechanisms Summary

This MCAT Organic Chemistry Mechanisms and Reactions Summary is by no means an exhaustive review of MCAT Organic Chemistry. Our summary is only meant to highlight key mechanisms that are most helpful for the new MCAT. Understanding the basics, like electrostatics (opposites attract, like charges repel), helps to minimize memorization and maximize the understanding of MCAT reaction mechanisms.

For a list of topics for the new MCAT: MCAT Organic Chemistry Topics List. You can also access practice questions in our Free MCAT Practice Test, or our many full-length MCAT Practice Tests.

R = alkyl Et = ethyl X = halide R^- MgX⁺ = Grignard reagent R^- Li⁺ = alkyl lithium

Grignard reagents and alkyl lithiums are special agents since they can create new C—C bonds (see ORG 1.6).

*Reduction involves the addition of hydrogen or subtraction of oxygen.

• Mild reducing agents add fewer hydrogens/subtract fewer oxygens.
• Strong reducing agents add more hydrogens/subtract more oxygens.

Cross-referencing to The Gold Standard MCAT text are found below.

Most reactions presented can be derived from basic principles (i.e. ORG 1.6, 7. 1). Many of the reactions are cross-referenced for further information.

• An acid chloride reacts with a Grignard reagent to produce a tertiary alcohol. See ORG 1.6, 9.1.
• An acid chloride reacts with a primary or secondary amine to produce an amide. See ORG 9.3 & 11.2.
• A carboxylic acid reacts with SOCl₂ or PCl₅ to produce an acid chloride. See ORG 9.1
• An acid chloride reacts with an alcohol (e.g. ethanol) to produce an ester. See ORG 9.4.
• An amide reacts with LiAlH₄ to produce an amine. See ORG 8.2, 9.3.
• A carboxylic acid reacts with an alcohol (e.g. ethanol) to produce an ester. See ORG 8.2.
• An ester reacts with LiAlH₄ to produce a primary alcohol. See ORG 8.2, 9.4.
• A carboxylic acid reacts with base to produce a carboxylate anion. See CHM 6.3 & ORG 8.1.
• An ester reacts with a Grignard reagent to produce a tertiary alcohol. See ORG 1.6, 8.1.1, 9.4.
• A Grignard reagent reacts with carbon dioxide to produce a carboxylic acid. See ORG 8.1.1.
• A nitrile reacts with aqueous acid to produce a carboxylic acid. See ORG 8.1.1.
• A carboxylate ion reacts with ethyl iodide to produce an ester.
• An alkyl halide reacts with Mg/ether to produce a Grignard reagent.
• An alkyl halide reacts with NaCN to produce a nitrile. See ORG 6.2.3.
• A nitrile reacts with LiAlH₄ to produce an amine. See ORG 8.2.
• A primary alcohol reacts with HBr to produce an alkyl halide.
• An acid chloride reacts with NaBH₄ to produce a primary alcohol. See ORG 8.2, 9.1.
• A primary alcohol reacts with CrO₃/pyridine to produce an aldehyde. See ORG 6.2.2, 7.2.1.
• A acid chloride reacts with H₂/Pd/C to produce an aldehyde. See ORG 7.1, 7.2.1, 9.1.
• An aldehyde reacts with NaBH₄ to produce a primary or secondary alcohol. See ORG 7.1, 8.2.
• An aldehyde reacts with KMnO₄ to produce a carboxylic acid. See ORG 7.2.1, 8.1.1.
• A carboxylic acid reacts with LiAlH₄ to produce a primary alcohol. See ORG 8.2.
• An imine reacts with NaBH₄ to produce a secondary amine. See 7.2.3, 8.2.
• An aldehyde reacts with a primary amine to produce an imine. See ORG 7.2.3.
• An aldehyde reacts with a Grignard reagent and ether to produce a secondary alcohol. See ORG 1.6, 7.1.
• An aldehyde reacts with aqueous NaCN. See ORG 7.1.
• A secondary alcohol reacts with Na₂CrO₇ or CrO₃/pyridine to produce a ketone. See ORG 6.2.2.
• A ketone reacts with NaBH₄ to produce a secondary alcohol. See ORG 7.2.1.
• An acetal reacts with aqueous acid to produce an aldehyde. See ORG 7.2.1/2.
• An aldehyde reacts with an alcohol (e.g. ethanol) and acid to produce an acetal. Note that using with less EtOH/H⁺, a hemiacetal will form. See ORG 7.2.2.
• A ketone reacts with a Grignard reagent to produce a tertiary alcohol. See ORG 1.6, 9.

Memorize at least the following IR spectra data for the MCAT:

• Approx. 3300 cm^-1 for -OH (alcohol functional group)
• Approx. 1700 cm^-1 for C=O (carbonyl functional group)

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