November 13, 2023
Relieving my strain might contribute to sustainable energy sources.
What molecule am I?
Image of Quadricyclane 3D Image of Quadricyclane

Quadricyclane is a highly strained tetracyclic hydrocarbon. Despite its strain energy of 78.7 kcal/mol, it is stable at low temperatures.

In 1961, the laboratories of two outstanding organic chemists reported the synthesis of quadricyclane by the sensitized ultraviolet irradiation of norbornadiene1 in solution. The feat was accomplished by George S. Hammond*, Nicholas J. Turro, and Alfred Fischer at Caltech (Pasadena, CA) and by William G. Dauben* and Robert L. Cargill at the University of California, Berkeley. In both papers, the authors called the compound the now-obsolete “quadricyclene”.

In the 1980s and again in the early 2000s, the photochemical conversion of norbornadiene to quadricyclane was proposed as a way to store solar energy; but back then it was thought that the Sun does not emit enough ultraviolet radiation to make this method practical. In a 2021 account of norbornadiene/quadricyclane photoswitches for molecular solar thermal energy storage applications, however, Jessica Orrego-Hernández, Ambra Dreos, and Kasper Moth-Poulsen* at Chalmers University of Technology (Gothenburg, Sweden) described liquid storage systems that can store solar energy for as long as 18 years. They also proposed solid-state coatings for windows that can store incoming sunlight.

In December 2022, Ning Li and colleagues at the Chinese Academy of Sciences (Dalian), Dalian National Laboratory for Clean Energy, and the University of Chinese Academy of Sciences (Beijing) reported that C12 quadricyclane derivatives made from cellulose-derived 2,5-hexanedione2 are ideal components of sustainable aviation fuels.

Quadricyclane hazard information

Hazard class*GHS code and hazard statement
Flammable liquids, category 2H225—Highly flammable liquid and vaporChemical Safety Warning
Acute toxicity, inhalation, category 2H330—Fatal if inhaledChemical Safety Warning

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

MOTW update

Fructose1 was the Molecule of the Week for August 28, 2017. This monosaccharide, also known as “fruit sugar”, is found not only in fruits, but also in many other sugar sources. It and glucose are the components of the disaccharide sucrose, or common sugar.

It is well known that overeating foods containing fructose and other sugars contributes to type 2 diabetes, high levels of low-density cholesterol and triglycerides, obesity, and even gene damage. In October, Mario Estévez and co-workers at the University of Extremadura (Cáceres, Spain) reported that sustained fructose consumption interferes with gastrointestinal function, and consequently the health, of laboratory rats (Rattus novergicus). Specifically, high intake of the sugar decreases protein digestibility and promotes changes in the physiological digestion of proteins, enhancing intestinal digestion rather than stomach digestion.

1. CAS Reg. No. 57-48-7.

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Quadricyclane fast facts

CAS Reg. No.278-06-8
SciFinder nomenclatureTetracyclo
Empirical formulaC7H8
Formula mass92.14 g/mol
AppearanceColorless liquid
Boiling point112 °C
Water solubilityInsoluble
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