Pyrrolidine

Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula (CH2)4NH. It is a cyclic secondary amine, also classified as a saturated heterocycle. It is a colourless liquid that is miscible with water and most organic solvents. It has a characteristic odor that has been described as "ammoniacal, fishy, shellfish-like".[3] In addition to pyrrolidine itself, many substituted pyrrolidines are known.

Pyrrolidine
Names
Preferred IUPAC name
Pyrrolidine
Other names
Azolidine
Azacyclopentane
Tetrahydropyrrole
Prolamine
Azolane
Identifiers
3D model (JSmol)
102395
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.227
EC Number
  • 204-648-7
1704
RTECS number
  • UX9650000
UNII
UN number 1922
Properties
C4H9N
Molar mass 71.123 g·mol−1
Appearance Clear colorless liquid
Density 0.866 g/cm3
Melting point −63 °C (−81 °F; 210 K)
Boiling point 87 °C (189 °F; 360 K)
Miscible
Acidity (pKa) 11.27 (pKa of conjugate acid in water),[1]

19.56 (pKa of conjugate acid in acetonitrile)[2]

-54.8·10−6 cm3/mol
1.4402 at 28°C
Hazards
Main hazards highly flammable, harmful, corrosive, possible mutagen
Safety data sheet MSDS
GHS pictograms
GHS Signal word Danger
H225, H302, H314, H318, H332
P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P301+312, P301+330+331, P303+361+353, P304+312, P304+340, P305+351+338, P310, P312, P321, P330, P363, P370+378, P403+235
NFPA 704 (fire diamond)
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. gasolineHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
3
1
Flash point 3 °C (37 °F; 276 K)
345 °C (653 °F; 618 K)
Related compounds
Related nitrogen heterocyclic compounds
 Pyrrole (aromatic with two double bonds)
Pyrroline (one double bond)
Pyrrolizidine (two pentagonal rings)
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 and synthesis

Industrial production

Pyrrolidine is prepared industrially by the reaction of 1,4-Butanediol and ammonia at a temperature of 165–200 °C and a pressure of 17–21 MPa in the presence of a cobalt- and nickel oxide catalyst, which is supported on alumina.[4]

The reaction is carried out in the liquid phase in a continuous tube- or tube bundle reactor, which is operated in the cycle gas method. The catalyst is arranged as a fixed-bed and the conversion is carried out in the downflow mode. The product is obtained after multistage purification and separation by extractive and azeotropic distillation.[4]

Laboratory synthesis

In the laboratory, pyrrolidine was usually synthesised by treating 4-chlorobutan-1-amine with a strong base:

Occurrence

Many modifications of pyrrolidine are found in natural and synthetic chemistry. The pyrrolidine ring structure is present in numerous natural alkaloids such as nicotine and hygrine. It is found in many drugs such as procyclidine and bepridil. It also forms the basis for the racetam compounds (e.g. piracetam, aniracetam). The amino acids proline and hydroxyproline are, in a structural sense, derivatives of pyrrolidine.

Nicotine contains an N-methylpyrrolidine ring linked to a pyridine ring.

Reactions

Pyrrolidine is a base. Its basicity is typical of other dialkyl amines.[5] Relative to many secondary amines, pyrrolidine is distinctive because of its compactness, a consequence of its cyclic structure.

Pyrrolidine is used as a building block in the synthesis of more complex organic compounds. It is used to activate ketones and aldehydes toward nucleophilic addition by formation of enamines (e.g. used in the Stork enamine alkylation):[6]

References
  1. Hall, H. K. (1957). "Correlation of the Base Strengths of Amines". Journal of the American Chemical Society. 79 (20): 5441–5444. doi:10.1021/ja01577a030.
  2. Kaljurand, I.; Kütt, A.; Sooväli, L.; Rodima, T.; Mäemets, V.; Leito, I.; Koppel, I. A. (2005). "Extension of the Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile to a Full Span of 28 pKa Units: Unification of Different Basicity Scales". The Journal of Organic Chemistry. 70 (3): 1019–1028. doi:10.1021/jo048252w. PMID 15675863.
  3. Pyrrolidine, The Good Scents Company
  4. Bou Chedid, Roland; Melder, Johann-Peter; Dostalek, Roman; Pastre, Jörg; Tan, Aik Meam. "Process for the preparation of pyrrolidine". Google Patents. BASF SE. Retrieved 5 July 2019.
  5. H. K. Hall, Jr. (1957). "Correlation of the Base Strengths of Amines". J. Am. Chem. Soc. 79 (20): 5441. doi:10.1021/ja01577a030.
  6. R. B. Woodward, I. J. Pachter, and M. L. Scheinbaum (1974). "2,2-(Trimethylenedithio)cyclohexanone". Organic Syntheses. 54: 39.CS1 maint: multiple names: authors list (link); Collective Volume, 6, p. 1014
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