Ahead of Valentine's Day, chemist Raychelle Burks explains why a rose smells sweet. (Reactions/American Chemical Society)

With Valentine's Day nearly here, you might be running out to buy a big old bouquet of roses — or hoping to receive a few from your sweetie. But what makes those flowers smell so sweet?

In her new series "Get to Know a Molecule" (sponsored by the American Chemical Society), chemist Raychelle Burks explains the fascinating chemistry of rose oxide.

Rose oxide, which produces the quintessential rose smell you experience when you take a whiff of the Damask Rose, is actually four different chemicals. Even though the four chemicals have the same atoms in the same order, some of their atoms are arranged differently in 3-D space. Because the four chemicals fit into different scent receptors with those unique shapes, our brains recognize them as different scents: Sweet, fruity, minty, and citrusy.

"Chemistry is full of these subtle differences," Burks says in the video. "Arranging atoms even slightly differently can mean that a rose by any other configuration doesn't smell as sweet."

For flowers, scent production is a tricky business. From Scienceline:

The creation of scent is a balancing act: plants must generate enough smell to induce insects to fertilize their flowers, but not so much that they waste energy and carbon. In fact, for many species, scent emission is not constant; snapdragons decrease scent production 36 hours after pollination.

But humans can capture those insect-luring scents and turn them into people-luring perfumes. The Damask Rose is one of the most important flowers in perfumery, and perfumers submerge them in chemicals like benzene to dissolve the plant matter while leaving aromatic chemicals intact.

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