L-cysteine - ball and stick model

The organic functional groups of focus with the new MCAT are the ones playing a prominent role in biochemistry.

Functional groups are combinations of atoms within organic molecules that are responsible for the reactivity of the molecules, and functional groups play a role in determining their physical properties. Although the chemical behavior of certain moeities may be modified by overall molecular structure, the approach to the reactivity of organic molecules through functional groups is a powerful analytical method. Every functional group has its own personality.

Understanding the behaviors of the main organic functional groups in organic chemistry is another way to describe, really, the discipline as a whole. Straight out organic chemistry comprises approximately one third of the Biological Sciences section of the MCAT typically, so there will be many instances on the test where your familiarity with the properties of various organic functional groups will play a role as a conceptual ground.

WikiPremed Resources

MCAT Essential Reaction Mechanisms
Mechanisms and explanations from the Organic Mechanisms Pocketbook

Functional Groups in Organic Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Organic Functional Groups
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Be prepared to identify the major organic functional groups.

Understand the affect of a particular functional group on the physical properties and solubility of an organic compound.

Become familiar with the acid-base properties of various functional groups.

Begin consolidating mastery of the organic mechanisms. Be familiar with the major types of reaction each functional group can undergo, able to easily answer the simpler genre of questions at this stage.

Suggested Assignments

There are several comprehensive treatments of Organic Chemistry on the web, perfectly calibrated for students preparing for the MCAT.  Tour the web resources for functional groups.  Start here.

Read the organic mechanisms in the Organic-Biochem Flipbook. Keep attention on the organic mechanisms for now, leaving the biochemistry mechanisms for later. The aim is to get an overall picture of the personality of each functional group. The mechanisms are also online here.

Conceptual Vocabulary for Organic Functional Groups

Alkanes, also known as Paraffins, are chemical compounds that consist only of the elements carbon and hydrogen linked together exclusively by single bonds.
An alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond.
An alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group
A ketone is either the functional group characterized by a carbonyl group linked to two other carbon atoms or a chemical compound that contains this functional group.
Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. When the oxygen atom is linked to a larger molecule the hydroxyl group is a functional group.
Propyl is the substituent form of the alkane propane.
Butyl is a four-carbon alkyl substituent derived from either of the two isomers of the alkane called butane.
An aldehyde is an organic compound containing a terminal carbonyl group.
Traditionally known as acetylenes or the acetylene series, the alkynes are hydrocarbons that have at least one triple bond between two carbon atoms.
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of a carboxyl group.
Ether is the general name for a class of chemical compounds which contain an ether group, which is an oxygen atom connected to two alkyl or aryl groups.
Amines are organic compounds and a type of functional group that contain nitrogen as the key atom, structurally resembling ammonia, but one or more hydrogen atoms is replaced by alkyl and aryl groups.
A carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom.
The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide.
Carbonate ester
A carbonate ester is a functional group in organic chemistry consisting of a carbonyl group flanked by two alkoxy groups.
Esters are a class of chemical compounds and functional groups consisting of an inorganic or organic acid in which at least one -hydroxyl group is replaced by an alkoxy group.
The phenyl group consists of six carbon atoms are arranged in a cyclic ring structure. A member of the aromatic family, this functional group is highly stable.
Acyl halide
An acyl halide (also known as an acid halide) is a chemical compound derived from an acid by replacing a hydroxyl group with a halide group.
An amide is an organic functional group characterized by a carbonyl group linked to a nitrogen atom.
A thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom. Often referred to as mercaptans, these compounds are the sulfur analogues of alcohols.
Acetyl (ethanoyl), is the term for a functional group which is the acyl of acetic acid.
A peroxide is a compound containing an oxygen-oxygen single bond.
A phosphate is an ester of phosphoric acid in organic chemistry.
An imine is a functional group or chemical compound containing a carbon-nitrogen double bond, often synthesised by the addition of an amine to a ketone or aldehyde followed by an elimination of water
Nitrates in organic chemistry are the result of the esterification of nitric acid with various alcohols.
The term sulfide refers to several types of chemical compounds containing sulfur in its lowest oxidation number of -2.
Disulfide bond
A disulfide bond is a single covalent bond derived from the coupling of thiol groups.
In organic chemistry nomenclature, a heteroatom is any atom that is not carbon or hydrogen.
Advanced terms that may appear in context in MCAT passages
An imide is a functional group consisting of two carbonyl groups bound to a primary amine or ammonia.
Azo compound
Azo compounds refer to synthetic inorganic chemical compounds bearing the functional group in which two alkyl or aryl groups are bound respectively to two doubly bound nitrogens.
The cyanate ion or functional group consists of one oxygen atom, one carbon atom, and one nitrogen atom, in that order.
A nitrile is any organic compound which has carbon and nitrogen triply bonded.
A nitrite is either a salt or an ester of nitrous acid.
Nitroso refers to a functional group in organic chemistry which has the general formula RNO.
A sulfone is a chemical compound containing a sulfonyl functional group attached to two carbon atoms. The central sulfur atom is twice double bonded to oxygen and has two further hydrocarbon substituents.
A sulfoxide is a chemical compound containing a sulfinyl functional group attached to two carbon atoms. Such a compound could be considered as an oxidized sulfide.
Thiocyanates are rganic compounds containing the functional group SCN.