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Functional Groups Flashcards for Organic Chemistry

This set covers the functional groups introduced in the first weeks of organic chemistry: what each one looks like, what its IUPAC suffix or prefix is, and how to tell similar groups apart (ketone vs aldehyde, ester vs ether, amide vs amine). The group list follows OpenStax Organic Chemistry. It does not cover reactions or mechanisms, which you should build as separate cards from your own course notes.

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Free Functional Groups flashcards: 29-card starter set

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Hydrocarbons, halides and simple heteroatom groups (11)

Alkene: structure and IUPAC suffix?

Contains a C=C double bond. Suffix -ene (ethene, propene).

Alkyne: structure and IUPAC suffix?

Contains a C triple bond C. Suffix -yne (ethyne, propyne).

Arene (aromatic ring): what is it and the simplest example?

A six-membered ring with alternating double and single bonds that behaves as one delocalized system. Benzene, C6H6, is the simplest example.

Alkyl halide: structure and how is it named?

A carbon bonded to F, Cl, Br or I (C-X). Named with a prefix: fluoro-, chloro-, bromo-, iodo- (chloromethane).

Alcohol: structure, suffix and example?

A hydroxyl group on a carbon (C-OH). Suffix -ol; example ethanol, CH3CH2OH. OH as a prefix is hydroxy-.

How do you classify an alcohol as primary, secondary or tertiary?

By the number of carbons attached to the carbon bearing the OH: one (primary), two (secondary), three (tertiary).

Phenol vs alcohol: what is the difference?

In a phenol the OH is attached directly to a benzene ring carbon. In an alcohol it is on an sp3 carbon.

Ether: structure and example?

An oxygen bonded to two carbons (C-O-C). Example: dimethyl ether, CH3OCH3. Named as alkoxy- (e.g. methoxy-) on a parent chain.

Thiol vs sulfide: how do they differ?

A thiol has an SH group on carbon (suffix -thiol, methanethiol); a sulfide has sulfur between two carbons (C-S-C, dimethyl sulfide). Thiols are the sulfur analogues of alcohols, sulfides of ethers.

Amine: structure, suffix and key property?

Nitrogen with a lone pair bonded to carbon (C-N); suffix -amine (methylamine). Amines are basic because of the nitrogen lone pair.

Nitrile: structure and suffix?

A carbon triple-bonded to nitrogen (C triple bond N). Suffix -nitrile (ethanenitrile, CH3CN).

The carbonyl family (C=O) (12)

What defines a carbonyl group?

A carbon double-bonded to oxygen (C=O). Aldehydes, ketones, carboxylic acids, esters, amides and acid chlorides all contain one.

Aldehyde: structure, suffix and example?

Carbonyl carbon bonded to at least one hydrogen (R-CHO), at the end of a chain. Suffix -al; example ethanal, CH3CHO.

Ketone: structure, suffix and example?

Carbonyl carbon bonded to two carbons (R-CO-R). Suffix -one; example propanone (acetone), CH3COCH3.

How do you tell an aldehyde from a ketone in a drawn structure?

Look at the carbonyl carbon: if it carries an H, it is an aldehyde; if it is bonded to two carbons, it is a ketone.

Carboxylic acid: structure, suffix and example?

A carbonyl carbon bonded to an OH (R-COOH). Suffix -oic acid; example ethanoic acid (acetic acid), CH3COOH. It is weakly acidic.

Ester: structure, naming pattern and example?

A carbonyl carbon bonded to an alkoxy oxygen (R-COO-R'). Named alkyl ...-oate; example methyl ethanoate (methyl acetate).

How is an ester formed from a carboxylic acid?

Acid + alcohol give ester + water (Fischer esterification, acid-catalyzed). The OH of the acid and the H of the alcohol are lost as water.

Amide: structure, suffix and example?

A carbonyl carbon bonded to nitrogen (R-CO-NR2). Suffix -amide; example ethanamide. Amide bonds link amino acids in proteins (peptide bonds).

Acid chloride: structure and suffix?

A carbonyl carbon bonded to chlorine (R-COCl). Suffix -oyl chloride; example ethanoyl chloride. Very reactive.

Thioester: what is it and how is it related to an ester?

A carbonyl carbon bonded to sulfur (R-CO-SR'), the sulfur analogue of an ester. Example: S-methyl ethanethioate.

Ester vs ether: how can you tell them apart?

Both have an oxygen between two carbon groups, but an ester has a C=O next to that oxygen. An ether has no carbonyl.

Amide vs amine: what is the difference?

An amide has nitrogen on a carbonyl carbon (C(=O)-N) and is essentially non-basic; an amine has nitrogen on an alkyl carbon and is basic.

Naming and recognition (6)

Which functional group gets the suffix when a molecule has several: acid, ester, amide, nitrile, aldehyde, ketone, alcohol, amine?

The highest-priority group, in that order: carboxylic acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine (acid halides rank between esters and amides). Lower-priority groups become prefixes (hydroxy-, amino-, oxo-).

What prefix names an OH group when a higher-priority group is present?

Hydroxy-. Example: 3-hydroxybutanoic acid, where the carboxylic acid takes the suffix.

Which functional group is in CH3CH2OH?

An alcohol (hydroxyl on carbon): ethanol.

Which functional groups are in aspirin (acetylsalicylic acid)?

A carboxylic acid, an ester (the acetyl group) and an aromatic ring.

Which of these are acidic and which basic: carboxylic acid, amine, alcohol?

Carboxylic acids are the most acidic of these; amines are basic; alcohols are very weakly acidic and generally treated as neutral.

Why do alcohols have higher boiling points than ethers of similar mass?

Alcohols can hydrogen-bond to each other through O-H. Ethers have no O-H so they cannot donate hydrogen bonds.

What this set covers

Covered

Hydrocarbon groups, halides, oxygen, nitrogen and sulfur groups, the carbonyl family, naming priority

Best used for

Organic chemistry I quizzes and the first exam; MCAT/pre-health review of group recognition

Not covered

Reactions, mechanisms, spectroscopy, biological groups such as phosphates in depth

Tip

Draw each structure on paper from the card name before flipping

How to study this set

Functional groups are visual, so draw them. Start with the structures, then the names, then the comparisons that exams love to test.

1
Day 1
Cover the answer and sketch each hydrocarbon and heteroatom group. Say the name and suffix aloud as you draw.
2
Days 2-4
Drill the carbonyl family in one sitting so you compare them side by side. Draw all six and circle the atom attached to the carbonyl carbon.
3
Week 2
Do the naming-priority cards using real structures from your homework. Mark each group in a drawn molecule and decide which one takes the suffix.
4
Final week
Quiz in reverse: start from a drawn molecule and name every group, including hidden ones like esters and amides.

Spaced repetition schedules each card to come back just before you would forget it, so reviews get shorter as your recall gets stronger. Cards you miss come back sooner.

Common mistakes to avoid

Confusing esters with ethers

Both have C-O-C, but only the ester has an adjacent C=O. Always look for the carbonyl first.

Calling any N group an amine

Nitrogen next to a carbonyl is an amide, and nitrogen triple-bonded to carbon is a nitrile. Check the neighbours of N.

Missing the priority order

Students name the alcohol instead of the acid in a molecule that has both. The acid wins the suffix; the alcohol becomes hydroxy-.

Mixing aldehyde and ketone endings

-al is always at the end of a chain; -one is in the middle. Aldehyde carbons carry an H.

Make your own from your notes

A starter set is a head start, not your whole course. Your class notes, slides and textbook are what your teacher actually tests, so turn them into cards too.

Put a drawn structure or SMILES-style description on the front and the group name, suffix and one example on the back.
Use your textbook chapter's functional group table as the source so the deck uses your course's naming conventions.
Make "spot the difference" cards (ester vs ether, amide vs amine) because those are the usual exam traps.
Do not put reactions on the same card; keep groups and reactions in separate decks.

Generate cards from a topic or notes Turn a PDF into flashcards

Functional Groups flashcards: questions

How many functional groups do I need to know for organic chemistry I?

Around fifteen to twenty. These include alkenes, alkynes, aromatics, halides, alcohols, ethers, amines, aldehydes, ketones, carboxylic acids, esters, amides, nitriles and thiols. Your course syllabus decides the exact list.

What is the difference between an ester and a carboxylic acid?

Both have R-C(=O)-O, but the acid ends in OH and the ester ends in O-R. Esters are formed from an acid plus an alcohol with loss of water.

Is the aromatic ring a functional group?

Yes, most textbooks including OpenStax list the arene (benzene ring) as a functional group. Its delocalized pi system gives it distinct reactivity.

Do I need IUPAC names or common names?

Learn both for the very common ones (acetic acid, acetone, formaldehyde). Exams usually require IUPAC names for new structures and recognise the common ones as well.

Does this deck cover reactions?

No. It covers recognising and naming groups. Reactions and mechanisms depend heavily on your course, so create those cards from your notes.

Sources and review

These cards are an independent study aid, not official exam content, and are not affiliated with or endorsed by any exam body or publisher. They were written by hand and checked against the sources below on 2026-10-17. Always confirm details with your course materials and the current official documents.

OpenStax Organic Chemistry: Functional Groups — Read for the table of functional groups, name endings and examples (alkene, alkyne, arene, halide, alcohol, ether, amine, nitrile, thiol, sulfide, aldehyde, ketone, carboxylic acid, ester, thioester, amide, acid chloride).
OpenStax Organic Chemistry: Naming Alkanes — Confirmed IUPAC is the naming system and that the suffix names the primary functional group. The full seniority order on the naming-priority card rests on standard IUPAC practice and was not fetched.

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