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 2 H225—Highly flammable liquid and vapor Chemical Safety Warning
Aspiration toxicity, category 1 H304—May be fatal if swallowed and enters airways Chemical Safety Warning
Skin corrosion/irritation, category 2 H315—Causes skin irritation Chemical Safety Warning
Acute toxicity, inhalation, category 4 H332—Harmful if inhaled Chemical Safety Warning
Reproductive toxicity, category 2 H361—Suspected of damaging fertility or the unborn child Chemical Safety Warning
Specific target organ toxicity, repeated exposure, category 2 H373—May cause damage to organs through prolonged or repeated exposure Chemical 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

Once a month we will bring you a newly discovered or developed molecule that has important implications for the future of chemistry or society in general. Look for it the third week of each month. Learn more about this month's Molecule of the Future below.

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fast facts

CAS Reg. No. 85213-22-5
Ethanone, 1-(3,4-dihydro-2H-pyrrol-5-yl)-
Empirical formula C6H9NO
Molar mass 111.14 g/mol
Appearance Colorless to yellow solid or liquid
Melting point 19° C
Boiling point 183° C
Water solubility Soluble
Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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