Functional Groups Flashcards – 37 Organic Chemistry Cards

All 37 cards

Groups by formula 19

C=C A carbon–carbon double bond. Propene is the second simplest alkene.
C=O Carbon double-bonded to oxygen, found in aldehydes, ketones, acids, esters and amides.
–COOH The group name for –C(=O)–OH. It is the part that makes a carboxylic acid acidic.
–C₆H₅ A benzene ring with one hydrogen removed. Phenol is a phenyl group on –OH.
C≡C A carbon–carbon triple bond. Acetylene, HC≡CH, is the simplest.
–OH The group name. It makes an alcohol on a chain. Inside –COOH it is part of an acid.
R–CHO A carbonyl, C=O, at the end of a chain. It has an H on the same carbon.
R–COCl A carbonyl carrying a chlorine: a reactive cousin of a carboxylic acid.
R–CONH₂ A carbonyl joined to a nitrogen. Amide bonds, as peptide bonds, link amino acids in proteins.
R–COOH A carboxyl group, –C(=O)–OH. Acetic acid, in vinegar, is one.
R–COO–R′ An acid whose –OH hydrogen is replaced by a carbon group. Many small esters have a pleasant smell.
R–CO–R′ A carbonyl, C=O, between two carbon groups. Acetone is the simplest.
R–C≡N A carbon triple-bonded to nitrogen. Acetonitrile is the simplest organic one.
R–NH₂ Ammonia with a hydrogen replaced by a carbon group. Methylamine is the simplest primary amine.
R–NO₂ A nitro group, –NO₂, on carbon. The group is strongly electron-withdrawing.
R–OH An –OH group on a carbon chain. Ethanol, CH₃CH₂OH, is one.
R–O–R′ One oxygen joined to two carbon groups. Diethyl ether is the classic example.
R–SH The sulfur version of an alcohol. The –SH group is also called a sulfhydryl group.
R–X, where X is F, Cl, Br or I An alkane with a halogen in place of a hydrogen. Chloromethane is one.

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Name the class of a molecule 18

(CH₃)₂CO Acetone, the simplest ketone.
CH₃CH=CH₂ Propene, also called propylene.
CH₃CHO Acetaldehyde, or ethanal.
(CH₃CH₂)₂O Diethyl ether, once used as an anesthetic.
CH₃CH₂OH Ethanol, the alcohol in drinks.
CH₃CH₂SH Ethanethiol, ethanol with sulfur in place of oxygen.
CH₃Cl Chloromethane, or methyl chloride.
CH₃CN Acetonitrile, the simplest organic nitrile.
CH₃COCl Acetyl chloride, made from acetic acid.
CH₃CONH₂ Acetamide, from ammonia and acetic acid.
CH₃COOCH₂CH₃ Ethyl acetate, used in nail polish remover.
CH₃COOH Acetic acid, the acid in vinegar.
CH₃NH₂ Methylamine, the simplest primary amine.
CH₃NO₂ Nitromethane, the simplest nitro compound.
CH₃OH Methanol, the simplest alcohol.
C₆H₅OH Phenol: a phenyl group bonded to –OH. It is also its own class of compound.
HCHO Formaldehyde, or methanal, the simplest aldehyde.
HC≡CH Acetylene, or ethyne.

How this list was compiled: Group formulas and example molecules checked against the Wikipedia article for each functional group and each example compound (Alcohol via Hydroxy group, Ether, Aldehyde, Ketone, Carboxylic acid, Ester, Amine, Amide, Thiol, Haloalkane, Alkene, Alkyne, Nitrile, Nitro compound, Acyl chloride, Carbonyl group; Ethanol, Methanol, Diethyl ether, Acetaldehyde, Formaldehyde, Acetone, Acetic acid, Ethyl acetate, Methylamine, Acetamide, Ethanethiol, Chloromethane, Propene, Acetylene, Acetonitrile, Nitromethane, Acetyl chloride, Phenol), all read 2026-09-23. Card wording is own work. Licence: own work

How it works

These functional groups flashcards show a condensed formula and you name the group: alcohol, ether, aldehyde, ketone, ester, amide and the rest. A second set gives real molecules to sort by class.

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Two sets

Groups by formula has 19 cards, from R–OH to R–COCl, plus the group names hydroxyl, carbonyl, carboxyl and phenyl. Name the class of a molecule gives 18 real compounds, such as CH₃COOH, to identify.

Flip, type or race

Flip shows the answer when you tap. Quiz marks what you type, and second names such as alkyl halide count. Timed counts how many you name in a minute. Print cards gives a double-sided deck.

R and R′ stand for carbon groups. An aldehyde has H on the carbonyl carbon; a ketone has carbon on both sides.
Ester and carboxylic acid differ in one place: the acid's –OH hydrogen becomes a carbon group in the ester.

Questions and answers

Which functional groups should I know for organic chemistry?

A first course usually starts with the ones in this deck: alkenes, alkynes, haloalkanes, alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, amines and amides, then thiols, nitriles, nitro compounds and acyl chlorides.

What is the difference between a hydroxyl and an alcohol?

Hydroxyl is the group, –OH. An alcohol is a compound with that group on a carbon chain. The deck asks both, so the group names and the class names stay separate.

Are there structure drawings?

No. Every card uses a condensed formula such as R–CO–R′, which is how many worksheets write them. Draw the structure on paper before you flip, for extra practice.