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Organic Chemistry: Functional Groups Quiz

Identify alcohols, aldehydes, ketones, carboxylic acids, esters, amines, amides and ethers, and predict basic reactions and properties. Good for Organic Chemistry 1 and AP Chemistry.

by Kill h.17 questionsCreated Nov 8, 2026, 08:03 PM

Chemistry· Organic Chemistry#organic-chemistry#functional-groups#chemistry

17 questions

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1
CH₃CH₂OH contains which functional group?
- Alcohol (hydroxyl)
- B
  Carboxylic acid
- C
  Ether
- D
  Aldehyde
An –OH bonded to a saturated carbon is an alcohol. This molecule is ethanol. Do not confuse it with a carboxylic acid, which has –OH on a C=O carbon (–COOH).
2
Which functional group is –COOH?
- A
  Ester
- Carboxylic acid
- C
  Aldehyde
- D
  Ketone
–COOH (a carbonyl carbon also bonded to –OH) is a carboxylic acid, such as acetic acid in vinegar. An ester has –COO– with a carbon group in place of the H.
3
Acetone, CH₃COCH₃, contains which functional group?
- A
  Aldehyde
- B
  Ester
- Ketone
- D
  Ether
The C=O carbon in acetone is bonded to two carbons, which makes it a ketone. In an aldehyde the carbonyl carbon is bonded to at least one hydrogen, so the group sits at the end of a chain (–CHO).
4
Which functional group gives many fruits their smell and forms when a carboxylic acid reacts with an alcohol?
- A
  Ether
- B
  Amide
- C
  Ketone
- Ester
Esters (R–COO–R') such as isoamyl acetate (banana) and ethyl butanoate (pineapple-like) are sweet-smelling. Ethers (R–O–R') have no carbonyl group.
5
Which functional group is present in CH₃CH₂NH₂?
- A
  Amide
- Amine
- C
  Nitrile
- D
  Imine
An –NH₂ bonded to an alkyl carbon is a (primary) amine; this one is ethylamine. An amide needs the nitrogen bonded to a carbonyl carbon (–CONH₂).
6
The peptide bond linking amino acids in proteins is which functional group?
- A
  Ester
- B
  Amine
- Amide
- D
  Ether
A peptide bond is –CO–NH–, an amide formed by condensation of a carboxylic acid group and an amine group, releasing water. Each amino acid has an amine group, but the link between them is an amide.
7
CH₃–O–CH₃ is an example of which functional group?
- A
  Alcohol
- Ether
- C
  Ester
- D
  Ketone
An oxygen bonded to two carbon groups is an ether (dimethyl ether). It has no O–H, so it cannot hydrogen-bond with itself, unlike its isomer ethanol.
8
Which molecular formula is an alkane?
- C₅H₁₂
- B
  C₅H₁₀
- C
  C₅H₈
- D
  C₆H₆
Alkanes follow : for n = 5 that is C₅H₁₂. C₅H₁₀ fits an alkene or cycloalkane, C₅H₈ an alkyne or diene, and C₆H₆ is benzene.
9
What is the IUPAC name of CH₃CH₂CH₂CH₃?
- A
  Propane
- B
  Pentane
- C
  Butene
- Butane
Four carbons in a chain with only single bonds is butane (meth-, eth-, prop-, but-). Butene would need a C=C double bond.
10
Heating a carboxylic acid with an alcohol and an acid catalyst (Fischer esterification) produces:
- A
  An ether and water
- B
  An amide and water
- An ester and water
- D
  A ketone and hydrogen gas
R–COOH + R'–OH ⇌ R–COO–R' + H₂O. It is a condensation reaction, and it is reversible, so removing water or using excess alcohol pushes it toward the ester.
11
Oxidizing 2-propanol (a secondary alcohol) gives:
- Propanone (acetone)
- B
  Propanal
- C
  Propanoic acid
- D
  No reaction
Secondary alcohols oxidize to ketones and stop there, because there is no H left on the carbonyl carbon to remove. Primary alcohols give aldehydes, then carboxylic acids. Tertiary alcohols resist oxidation.
12
Ethanol is fully oxidized with an excess of a strong oxidizing agent such as acidified potassium dichromate. What is the final product?
- A
  Ethanal
- B
  Ethene
- Ethanoic (acetic) acid
- D
  Ethoxyethane
Primary alcohol → aldehyde (ethanal) → carboxylic acid (ethanoic acid). To stop at the aldehyde you must distill it off as it forms. This reaction is the basis of the old dichromate breathalyzer.
13
Butane and 2-methylpropane are both C₄H₁₀. They are:
- A
  The same compound
- B
  Enantiomers
- C
  Different alkenes
- Structural (constitutional) isomers
Same molecular formula, different connectivity: a straight chain versus a branched chain. Enantiomers are mirror-image stereoisomers, which requires a chiral center.
14
Which compound has the highest boiling point?
- A
  Dimethyl ether, CH₃OCH₃
- Ethanol, CH₃CH₂OH
- C
  Propane, CH₃CH₂CH₃
- D
  Acetaldehyde, CH₃CHO
All four have similar molar masses (44–46 g/mol), but only ethanol can hydrogen-bond with itself through its O–H group. It boils at 78 °C, compared with about 20 °C for acetaldehyde and below 0 °C for the ether and propane.
15
Why does benzene usually undergo substitution rather than addition reactions?
- A
  Benzene has no double bonds at all
- B
  Benzene is a saturated hydrocarbon
- Substitution keeps the stable aromatic ring of delocalized electrons intact
- D
  Addition reactions only work on alkanes
Benzene's six pi electrons are delocalized around the ring, giving extra aromatic stability. Addition would destroy that, so electrophilic substitution, which keeps the ring, is favored.
16
A carbon atom is a chiral center when it is bonded to:
- A
  Two identical groups
- B
  A double-bonded oxygen
- Four different groups
- D
  Three hydrogen atoms
Four different substituents make the molecule non-superimposable on its mirror image, giving two enantiomers. A carbonyl carbon has only three groups, so it cannot be a chiral center.
17
Bromine water is orange-brown. Which compound decolorizes it quickly at room temperature?
- A
  Ethane
- Ethene
- C
  Benzene
- D
  Ethanol
Alkenes add Br₂ across the C=C double bond, which uses up the bromine and removes the color. Alkanes have no double bond, and benzene resists addition because of its aromatic stability.