Functional Group Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Functional Group.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A functional group is a specific arrangement of atoms in an organic molecule that gives the molecule characteristic chemical properties and typical reactions.

The functional group is the part of an organic molecule that most strongly controls how it behaves.

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How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Functional Group starts by identifying the carbon skeleton, functional group, and repeating pattern if present.

Common stuck point: Students often know a formula related to functional group but skip the recognition step: Am I using carbon structure, bonds, functional groups, or repeating units to explain the molecule? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I using carbon structure, bonds, functional groups, or repeating units to explain the molecule?

Worked Examples

Example 1

medium
Why is ethanoic acid (CH3COOHCH_3COOH) more acidic than ethanol (CH3CH2OHCH_3CH_2OH)?

Answer

The −COOH group readily releases H+ (stabilized conjugate base)\text{The } -COOH \text{ group readily releases } H^+ \text{ (stabilized conjugate base)}

First step

1
−COOH-COOH's conjugate base −COO−-COO^- is resonance-stabilized.

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Example 2

medium
Predict whether butan-2-one (CH3COCH2CH3CH_3COCH_2CH_3) can form hydrogen bonds with itself. With water?

Example 3

hard
Why are amino acids zwitterionic in aqueous solution at neutral pH?

Example 4

hard
Predict the products of esterification between ethanoic acid and methanol with acid catalysis.

Example 5

challenge
A drug candidate has a phenol and a primary amine. How would you expect its solubility and acid-base behavior to differ between pH 2, pH 7, and pH 12?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Which functional group is represented by −OH-OH?

Example 2

easy
Which functional group is −COOH-COOH?

Example 3

easy
A functional group is the part of a molecule that mostly controls its what?

Example 4

easy
What family does a molecule with a −COOH-COOH group belong to?

Example 5

easy
Ethanol contains which functional group?

Example 6

easy
Do functional groups affect a molecule's polarity?

Example 7

easy
Which functional group makes a molecule acidic: hydroxyl or carboxyl?

Example 8

easy
Can two molecules with the same formula have different functional groups?

Example 9

medium
Ethanol (C2H5OHC_2H_5OH) and dimethyl ether (CH3OCH3CH_3OCH_3) share formula C2H6OC_2H_6O. Name each functional group.

Example 10

medium
Acetic acid and ethanol differ by one functional group. Which is acidic and why?

Example 11

medium
Why is methanol (CH3OHCH_3OH) far more water-soluble than methane (CH4CH_4)?

Example 12

medium
A molecule is named an aldehyde. Without its formula, what can you predict about its reactions?

Example 13

medium
Why do carboxylic acids generally have higher boiling points than alcohols of similar size?

Example 14

medium
Identify the functional group that defines an amine, and the element it contains.

Example 15

medium
Two compounds, C3H8OC_3H_8O, are an alcohol and an ether. Explain why they smell and react differently.

Example 16

medium
Which functional group is present in a ketone, and what atom does it center on?

Example 17

medium
Why does adding a polar functional group usually raise a molecule's boiling point?

Example 18

challenge
A molecule contains both an −OH-OH and a −COOH-COOH group (like lactic acid). Predict whether it is more water-soluble than a similar-size hydrocarbon, and whether it is acidic.

Example 19

challenge
Why can a single change of functional group (e.g., −OH-OH to −COOH-COOH) drastically change a molecule's chemistry while the carbon skeleton stays the same?

Example 20

challenge
Glucose has multiple −OH-OH groups. Explain, using functional groups, why it dissolves readily in water but not in oil.

Example 21

easy
Which functional group is represented by −NH2-NH_2?

Example 22

easy
Which functional group is −CHO-CHO?

Example 23

easy
Methanol (CH3OHCH_3OH) contains which functional group?

Example 24

easy
An ester contains which arrangement of atoms?

Example 25

easy
Which functional group is in dimethyl ether (CH3OCH3CH_3OCH_3)?

Example 26

easy
Which family of compounds contains the C=CC=C double bond as its defining feature?

Example 27

medium
Propanal (CH3CH2CHOCH_3CH_2CHO) and propanone (CH3COCH3CH_3COCH_3) share C3H6OC_3H_6O. Name each functional group.

Example 28

medium
Aspirin contains both an ester linkage and a carboxylic acid group. What can you predict about its acidity and reactivity?

Example 29

medium
An amide has the structure R−CO−NH2R-CO-NH_2. Which two functional groups appear to combine in it?

Example 30

medium
Why does adding a hydroxyl group to a hydrocarbon raise its boiling point dramatically?

Example 31

medium
Compare 1-propanol and 2-propanol. Do they share the same functional group? Will they have similar reactivity?

Example 32

medium
A compound has formula C2H4O2C_2H_4O_2 and turns blue litmus red. Which functional group does it likely contain?

Example 33

medium
A molecule contains an −NH2-NH_2 group. Will it generally act as a Bronsted-Lowry acid or base?

Example 34

medium
Phenol (C6H5OHC_6H_5OH) and cyclohexanol (C6H11OHC_6H_{11}OH) both have −OH-OH, but phenol is acidic and cyclohexanol is not. Explain briefly.

Example 35

hard
Identify the functional groups in glycine, H2N−CH2−COOHH_2N-CH_2-COOH.

Example 36

hard
A molecule has −OH-OH, −COOH-COOH, and a C=CC=C double bond. Predict three different reactions it can undergo.

Example 37

hard
A compound has formula C3H6OC_3H_6O. List three possible functional group families and one isomer for each.

Example 38

hard
Why is a primary alcohol more easily oxidized than a tertiary alcohol?

Example 39

hard
Why do amide linkages in proteins resist hydrolysis at body temperature but break easily with enzymes?

Example 40

hard
Phenol is roughly 10610^6 times more acidic than ethanol. Identify the functional groups present in each and the structural reason.

Example 41

challenge
Cellulose, starch, and glycogen are all polymers of glucose differing in glycosidic linkage. Which functional group reaction connects monomer units?
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Related Concepts

Organic Chemistry

Background Knowledge

These ideas may be useful before you work through the harder examples.

organic chemistry