Propionaldehyde or propanal is the

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the formula CH₃CH₂CHO. It is the 3-carbon

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl gro ...

. It is a colourless, flammable liquid with a slightly fruity odour. It is produced on a large scale industrially.

Production

Propionaldehyde is mainly produced industrially by

hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon ...

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene ...

: :CO + H₂ + C₂H₄ → CH₃CH₂CHO In this way, several hundred thousand tons are produced annually.

Laboratory preparation

Propionaldehyde may also be prepared by oxidizing

1-propanol Propan-1-ol (also propanol, n-propyl alcohol) is a primary alcohol with the formula and sometimes represented as PrOH or ''n''-PrOH. It is a colorless liquid and an isomer of 2-propanol. It is formed naturally in small amounts during many fer ...

with a mixture of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

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 Propionic acid (, from the Greek words πρῶτος : ''prōtos'', meaning "first", and πίων : ''píōn'', meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2CO2H. It is a li ...

Reactions

Propionaldehyde exhibits the reactions characteristic of alkyl

s, e.g. hydrogenation, aldol condensations, oxidations, etc. It is the simplest aldehyde with a prochiral methylene such that α-functionalized derivatives (CH₃CH(X)CHO) are

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...

Uses

It is predominantly used as a precursor to trimethylolethane (CH₃C(CH₂OH)₃) through a

condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...

with

formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

. This triol is an important intermediate in the production of

alkyd An alkyd is a polyester resin modified by the addition of fatty acids and other components. Alkyds are derived from polyols and organic acids including dicarboxylic acids or carboxylic acid anhydride and triglyceride oils. The term ''alkyd'' is a m ...

resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on nat ...

s. 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.

Laboratory uses

Propionaldehyde is a common reagent, being a building block to many compounds. Many of these uses exploit its participation in condensation reactions. With ''tert''-butylamine it gives CH₃CH₂CH=N-''t''-Bu, a three-carbon building block used in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

Extraterrestrial occurrence

Propionaldehyde along with

acrolein Acrolein (systematic name: propenal) is the simplest unsaturated aldehyde. It is a colorless liquid with a piercing, acrid smell. The smell of burnt fat (as when cooking oil is heated to its smoke point) is caused by glycerol in the burning fat ...

has been detected in the

molecular cloud A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydroge ...

Sagittarius B2 near the center of the

Milky Way Galaxy The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

, about 26,000 light years from Earth.Chemical Precursors to Life Found in Space Scientists say that a universal prebiotic chemistry may be at work
/ref> Measurements by the COSAC and Ptolemy instruments on

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

67/P surface, revealed sixteen

s, four of which were seen for the first time on a comet, including

acetamide Acetamide (systematic name: ethanamide) is an organic compound with the formula CH3CONH2. It is the simplest amide derived from acetic acid. It finds some use as a plasticizer and as an industrial solvent. The related compound ''N'',''N''-dime ...

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscibl ...

methyl isocyanate Methyl isocyanate (MIC) is an organic compound with the molecular formula CH3NCO. Synonyms are isocyanatomethane and methyl carbylamine. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, ...

and propionaldehyde.

Safety

With an

LD50 In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the ...

of 1690 mg/kg (oral), propionaldehyde exhibits low acute toxicity.

References

{{Authority control Aldehydes Hazardous air pollutants