Not to be confused with propanol.
IUPAC name
Systematic IUPAC name
Other names
  • Methylacetaldehyde
  • Propionic aldehyde
  • Propaldehyde
123-38-6 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:17153 YesY
ChEMBL ChEMBL275626 YesY
ChemSpider 512 YesY
ECHA InfoCard 100.004.204
PubChem 527
UN number 1275
Molar mass 58.08 g·mol−1
Appearance Colorless liquid
Pungent, fruity odor
Density 0.81 g cm−3
Melting point −81 °C (−114 °F; 192 K)
Boiling point 46 to 50 °C (115 to 122 °F; 319 to 323 K)
20 g/100 mL
Viscosity 0.6 cP at 20 °C
C1, O: sp2

C2, C3: sp3

2.52 D
F+ Xi
R-phrases R11, R36/37/38
S-phrases S9, S16, S29
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point −26 °C (−15 °F; 247 K)
175 °C (347 °F; 448 K)
Related compounds
Related aldehydes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Propionaldehyde or propanal is the organic compound with the formula CH3CH2CHO. It is a saturated 3-carbon aldehyde and is a structural isomer of acetone. It is a colorless liquid with a slightly irritating, fruity odor.


Propionaldehyde is mainly produced industrially through hydroformylation, by combining synthesis gas (carbon monoxide and hydrogen) with ethylene using a metal (typically rhodium) catalyst:

CO + H2 + C2H4 → CH3CH2CHO

In this way, several hundred thousand tons are produced annually.[1]

Laboratory preparation

Propionaldehyde may also be prepared by oxidizing 1-propanol with a mixture of sulfuric acid and potassium dichromate. The reflux condenser contains water heated at 60 °C, which condenses unreacted propanol, but allows propionaldehyde to pass. The propionaldehyde vapor is immediately condensed into a suitable receiver. In this arrangement, any propionaldehyde formed is immediately removed from the reactor, thus it does not get over-oxidized to propionic acid.[2]


It is principally used as a precursor to trimethylolethane (CH3C(CH2OH)3) through a condensation reaction with formaldehyde; this triol is an important intermediate in the production of alkyd resins. Other applications include reduction to propanol and oxidation to propionic acid.[1]

Condensation of propionaldehyde with tert-butylamine gives CH3CH2CH=N-t-Bu, a three-carbon building block used in organic synthesis. Deprotonation of this imine with LDA produces CH3CHLiCH=N-t-Bu, which in turn condenses with aldehydes.[3]

Extraterrestrial occurrence

Astronomers have detected propionaldehyde (along with acrolein) in the molecular cloud Sagittarius B2 near the center of the Milky Way Galaxy, about 26,000 light years from Earth.[4][5][6]

On 30 July 2015, scientists reported that upon the first touchdown of the Philae lander on comet 67/P's surface, measurements by the COSAC and Ptolemy instruments revealed sixteen organic compounds, four of which were seen for the first time on a comet, including acetamide, acetone, methyl isocyanate and propionaldehyde.[7][8][9]


  1. 1 2 Anthony J. Papa "Propanal" In Ullmann's Encyclopedia of Industrial Chemistry, 2011, WIley-VCH, Weinheim. doi:10.1002/14356007.a22_157.pub2
  2. Charles D. Hurd and R. N. Meinert (1943). "Propionaldehyde". Org. Synth.; Coll. Vol., 2, p. 541
  3. Peralta, M. M. "Propionaldehyde t-Butylimine" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.
  4. Scientists Discover Two New Interstellar Molecules: Point to Probable Pathways for Chemical Evolution in Space, National Radio Astronomy Observatory, June 21, 2004
  5. Two newly found space molecules. By: Goho, Alexandra, Science News, 00368423, 7/24/2004, Vol. 166, Issue 4
  6. Chemical Precursors to Life Found in Space Scientists say that a universal prebiotic chemistry may be at work
  7. Jordans, Frank (30 July 2015). "Philae probe finds evidence that comets can be cosmic labs". The Washington Post. Associated Press. Retrieved 30 July 2015.
  8. "Science on the Surface of a Comet". European Space Agency. 30 July 2015. Retrieved 30 July 2015.
  9. Bibring, J.-P.; Taylor, M.G.G.T.; Alexander, C.; Auster, U.; Biele, J.; Finzi, A. Ercoli; Goesmann, F.; Klingehoefer, G.; Kofman, W.; Mottola, S.; Seidenstiker, K.J.; Spohn, T.; Wright, I. (31 July 2015). "Philae's First Days on the Comet - Introduction to Special Issue". Science. 349 (6247): 493. Bibcode:2015Sci...349..493B. doi:10.1126/science.aac5116. Retrieved 30 July 2015.
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