Propionaldehyde

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 colourless, flammable liquid with a slightly irritating, fruity odour.

Not to be confused with propanol.
Propionaldehyde
Skeletal formula of propionaldehyde (propanal)
Flat structure
Names
IUPAC name
Propanal
Systematic IUPAC name
Propanal
Other names
  • Methylacetaldehyde
  • Propionic aldehyde
  • Propaldehyde
Identifiers
CAS Number
3D model (JSmol)
3DMet
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.204
EC Number
  • 204-623-0
KEGG
PubChem CID
RTECS number
  • UE0350000
UNII
UN number 1275
CompTox Dashboard (EPA)
Properties
Chemical formula
 C3H6O
Molar mass 58.080 g·mol−1
Appearance Colourless liquid
Odor Pungent, fruity
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)
Solubility in water
 20 g/100 mL
Magnetic susceptibility (χ)
 -34.32·10−6 cm3/mol
Viscosity 0.6 cP at 20 °C
Structure
Molecular shape
 C1, O: sp2

C2, C3: sp3

Dipole moment
 2.52 D
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H225, H302, H332, H315, H318, H335[1]
GHS precautionary statements
 P210, P261, P280, P304+340+312, P305+351+338, P310, P403+235[1]
NFPA 704 (fire diamond)
3
2
2
Flash point −26 °C (−15 °F; 247 K)
Autoignition
temperature
 175 °C (347 °F; 448 K)
Related compounds
Related aldehydes
 Acetaldehyde
Butyraldehyde
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

Production

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.[2]

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.[3]

Uses

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. It is used in the synthesis of several common aroma compounds (cyclamen aldehyde, helional, lilial). Other applications include reduction to propanol and oxidation to propionic acid.[2]

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.[4]

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.[5][6][7]

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.[8][9][10]

References
  1. Record of Propanal in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on 22 March 2020.
  2. Anthony J. Papa "Propanal" In Ullmann's Encyclopedia of Industrial Chemistry, 2011, WIley-VCH, Weinheim. doi:10.1002/14356007.a22_157.pub2
  3. Charles D. Hurd and R. N. Meinert (1943). "Propionaldehyde". Organic Syntheses.; Collective Volume, 2, p. 541
  4. 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.
  5. Scientists Discover Two New Interstellar Molecules: Point to Probable Pathways for Chemical Evolution in Space, National Radio Astronomy Observatory, June 21, 2004
  6. Two newly found space molecules. By: Goho, Alexandra, Science News, 00368423, 7/24/2004, Vol. 166, Issue 4
  7. Chemical Precursors to Life Found in Space Scientists say that a universal prebiotic chemistry may be at work
  8. Jordans, Frank (30 July 2015). "Philae probe finds evidence that comets can be cosmic labs". The Washington Post. Associated Press. Retrieved 30 July 2015.
  9. "Science on the Surface of a Comet". European Space Agency. 30 July 2015. Retrieved 30 July 2015.
  10. 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. PMID 26228139.