November 15, 2021
I’m formed when you cook rice or bake bread.
What molecule am I?
Image of 2-Acetyl-1-pyrroline

November is flavor and aroma month at MOTW!

2-Acetyl-1-pyrroline (2AP) is a ketone derivative of the heterocyclic compound 1-pyrroline. The hazard information table shows that the pure compound has some dangerous properties, but you probably know it from its pleasing aroma.

In 1982, Ron G. Buttery and Louisa C. Ling at the US Department of Agriculture (Albany, CA) and Bienvenido Juliano at the International Rice Research Institute (Los Baños, Philippines) identified 2AP as an important aroma component of cooked rice. It is present in the volatile oils of basmati and Calrose rice. The researchers also synthesized 2AP via the catalytic reduction of 2-acetylpyrrole, followed by oxidation with silver carbonate.

The following year, the same authors identified 2AP in the leaves of the tropical plant pandan (Pandanus amaryllifolius). The leaves are used as a flavoring agent in south and southeast Asia.

Later in the 1980s, chemists began to identify 2AP in the aroma of baking bread. In 1985, Peter Schieberle and Werner Grosch at what is now the Technical University of Munich (Garching, West Germany) reported that the compound, in addition to other flavor and aroma ingredients, is present in the crusts of wheat and rye breads. 2AP is formed by the Maillard reaction that is characteristic of baking bread, in which amino acids and reducing sugars react to form the components of the crust’s brown color.

Curiously, on a less appealing note, 2AP also contributes to the urine odor of several Asian mammals, including the bintarong (Arctictis binturong; aka the bearcat) and three subspecies of tiger (Panthera tigris).

2-Acetyl-1-pyrroline hazard information

Hazard class*GHS code and hazard statement
Flammable liquids, category 2H225—Highly flammable liquid and vaporChemical Safety Warning
Aspiration toxicity, category 1H304—May be fatal if swallowed and enters airwaysChemical Safety Warning
Skin corrosion/irritation, category 2H315—Causes skin irritationChemical Safety Warning
Acute toxicity, inhalation, category 4H332—Harmful if inhaledChemical Safety Warning
Reproductive toxicity, category 2H361—Suspected of damaging fertility or the unborn childChemical Safety Warning
Specific target organ toxicity, repeated exposure, category 2H373—May cause damage to organs through prolonged or repeated exposureChemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Molecule of the future

Polybutylene adipate-co-terephthalate1 (PBAT) is a copolymer that consists of two units: the 1,4-butanediol monoester of terephthalic acid and the 1,4-butanediol monoester of adipic acid (hexanedioic acid). The two units are dispersed randomly throughout the length of the copolymer.

PBAT molecule

PBAT has gained much traction recently because it is a potential biodegradable replacement for conventional plastic polymers. Even though all of its components are petrochemicals, the copolymer’s ester linkages give it decomposition properties similar to those of two other developmental biodegradable polymers, poly(lactic acid) and poly(hydroxyalkanoate).

The physical properties of PBAT are comparable with those of low-density polyethylene, which is used to make stretchable films for food-packaging bags, trash bags, and the like. Corporations worldwide are moving rapidly to increase production of PBAT.

1. CAS Reg. No. 60961-73-1.

Molecule of the Future

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fast facts

CAS Reg. No.85213-22-5
Ethanone, 1-(3,4-dihydro-2H-pyrrol-5-yl)-
Empirical formulaC6H9NO
Molar mass111.14 g/mol
AppearanceColorless to yellow solid or liquid
Melting point19° C
Boiling point183° C
Water solubilitySoluble
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