Benzaldehyde

An aromatic aldehyde that can oxidise to benzoic acid.

Formula
C7H6O
Functional group
Aldehydes
Molar mass
106.12 g/mol
Also known as
Benzoic aldehyde, Phenylmethanal, Benzenecarbonal, Benzenecarboxaldehyde, Benzenemethylal, Benzaldehyde FFC

Overview

An aromatic aldehyde that can oxidise to benzoic acid.

The CHO group is attached directly to a benzene ring. Oxidation changes that aldehyde group into a carboxyl group while retaining the ring in the usual transformation. The aldehyde carbon bears a hydrogen, distinguishing it from aromatic ketones such as acetophenone.

Identifiers

Formula
C7H6O
Functional group
Aldehydes
Molar mass
106.12 g/mol
Also known as
Benzoic aldehyde, Phenylmethanal, Benzenecarbonal, Benzenecarboxaldehyde, Benzenemethylal, Benzaldehyde FFC
Chemical identifiers
SMILES
C1=CC=C(C=C1)C=O
InChI
InChI=1S/C7H6O/c8-6-7-4-2-1-3-5-7/h1-6H
PubChem CID
240

Properties

Melting Point
-57.12 °C
Boiling Point
178.7 °C
Relative density (water = 1)
Relative density (water = 1): 1.05
Water solubility
In water, 6950 mg/L at 25 °C

Diagnostic tests

Tollens’ aldehyde test

Reagent
freshly prepared Tollens’ reagent
Conditions
Gentle water-bath warming with adequate phase contact.
Positive observation
Metallic silver forms under suitable test conditions.
Negative observation
No silver deposit with an ordinary nonreducing ketone control.
Interpretation
The aldehyde group is oxidised to benzoate in the alkaline reagent.
Scope
Expected positive from benzaldehyde’s aldehyde group.
Limitations
Phase contact affects response time; the test detects the functional group.
Evidence
established functional-group chemistry

Related compounds

  • Aldehydes

    An aromatic aldehyde that can oxidise to benzoic acid.

Connected reactions

  • Carbonyl reduction: Benzaldehyde → Benzyl alcohol

    Hydride attacks the aldehyde carbon and the C=O pi electrons move to oxygen. Protonation of the alkoxide gives benzyl alcohol; neither a new carbon-carbon bond nor reduction of the aromatic ring is involved.

  • Aldehyde oxidation: Benzaldehyde → Benzoic acid

    Water reversibly adds to the aldehyde to form a hydrate, which can then be oxidised. The aldehyde carbon becomes the acid carbonyl carbon; acid work-up converts the initially formed benzoate into benzoic acid.

References

  1. PubChem Compound Summary: Benzaldehyde (CID 240)National Center for Biotechnology Information · PubChem

    Identity, molecular formula, molecular weight and aliases retrieved via PUG REST on 2026-09-08.

  2. OpenStax Organic Chemistry: Oxidation of aldehydes and ketonesJohn McMurry · OpenStax · 2023

    Supports the qualitative structural interpretation of the recorded molecular structure; no new physical measurement or verified preparative yield is claimed.

  3. Hazardous Substances Data Bank (HSDB): Benzaldehyde — melting pointHazardous Substances Data Bank (HSDB)

    Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/240#section=Melting-Point. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 3-34

  4. Hazardous Substances Data Bank (HSDB): Benzaldehyde — boiling pointHazardous Substances Data Bank (HSDB)

    Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/240#section=Boiling-Point. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Haynes, W.M. (ed.). CRC Handbook of Chemistry and Physics. 95th Edition. CRC Press LLC, Boca Raton: FL 2014-2015, p. 3-24

  5. ILO-WHO International Chemical Safety Cards (ICSCs): Benzaldehyde — densityILO-WHO International Chemical Safety Cards (ICSCs)

    Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/240#section=Density. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred.

  6. Hazardous Substances Data Bank (HSDB): Benzaldehyde — solubilityHazardous Substances Data Bank (HSDB)

    Retrieved through PubChem PUG View on 2026-09-08. https://pubchem.ncbi.nlm.nih.gov/compound/240#section=Solubility. Source value, complete property clause or compact miscibility statement retained; absent pressure, temperature or phase conditions are not inferred. Original reference: Yalkowsky, S.H., He, Yan, Jain, P. Handbook of Aqueous Solubility Data Second Edition. CRC Press, Boca Raton, FL 2010, p. 367

  7. The silver mirror test with Tollens’ reagentRoyal Society of Chemistry · RSC Education

    Source-supported qualitative reference observations.