Flavor the Month: Watermelon

Nothing says “summer” quite like a big, juicy slice of watermelon. Even if you prefer it charred on the grill or blended into an icy agua fresca, watermelon is one of the best ways to beat the late-summer heat.

So what gives watermelon its refreshingly delicate flavor?

Turns out the answer is pretty complicated. Over the last few decades, scientists have identified dozens of flavor and aroma molecules that contribute to watermelon’s unique taste.

And here’s an interesting twist: a watermelon’s flavor has a lot to do with its color. Chow down on a yellow ‘Early Moonbeam,’ a pale ‘Cream of Saskatchewan,’ or a deep red ‘Crimson Sweet’ and you’ll likely notice different flavor profiles for each melon. Read more… 

Photo credit: David MacTavish/Hutchinson Farm

anonymous said:

How did you study for IR spec in OChem?! I just can't make sense of this ;(

I found IR fairly simple (compared to other analytical methods). Different functional groups correspond to different IR spectra which can be identified by their wavenumber.

Is there anything in particular that is troubling you?

Fractional distillation on atmospheric pressure.

To keep the Vigreux column on permanent temperature on the full of its length, we often wrap it in glass wool or aluminium foil, or both. The glass keeps the heat inside, the aluminium foil acts as a heat mirror, so it also keeps most of the heat inside. 

The brown thing what looks like as the fur of a bear is a piece of glass wool.

Why is this important? If the temperature is permanent, component A what has a boiling point 125 °C will distill till the whole glass apparatus is on a temperature 125 °C and component B which has a boiling point 142 °C will only start to distill after it. But if the surrounding air lets the heat escape, the distilling column will have places where it can cool down under 125 °C, while other parts are much hotter than 142 °C, so a mixture of the who compounds will distill to the receiving flask.

GRAPHENE’S DARK SIDE

Graphene is one popular nanomaterial. Made from single-atom-thick sheets of carbon, it is the strongest material ever tested and boasts superlative electronic properties, too. After a decade of research, it is on the verge of moving from the laboratory into commercial technologies, perhaps appearing soon as lightweight airplane parts or batteries with incredible capacities.

So now might be a good time to anticipate potential risks posed by graphene, before workers are exposed to it or it gets into the water supply, says Sharon Walker, an environmental engineer at the University of California, Riverside. In research described in May in Environmental Engineering Science, Walker’s group observed how one form of the material, graphene oxide, behaves in water.

  • In groundwater, which typically has a higher degree of hardness and a lower concentration of natural organic matter, the graphene oxide nanoparticles tended to become less stable and eventually settle out or be removed in subsurface environments.
  • In surface waters, where there is more organic material and less hardness, the nanoparticles remained stable and moved farther, especially in the subsurface layers of the water bodies.
  • Graphene oxide nanoparticles, despite being nearly flat, as opposed to spherical, like many other engineered nanoparticles, follow the same theories of stability and transport.

Walker found that in a solution mimicking groundwater, graphene oxide clumped and sank, suggesting it is not a risk. That was not the case in a solution mimicking surface water, which includes lakes and storage tanks for drinking water. Instead of falling to the bottom, it stuck to the organic matter produced by decomposing plants and animals and floated around. Such mobility might increase the chances that animals and people could ingest graphene oxide, which has shown toxicity in some early studies in mice and human lung cells

2

Antoine Lavoisier - Scientist of the Day

Antoine Lavoisier, a French chemist, was born Aug. 26, 1743. Lavoisier is rightly considered the father of the chemical revolution of the late 18th century, and he is remarkable for having achieved this stature without discovering a single new element or gas or any other natural phenomenon. Oxygen, hydrogen, nitrogen, and carbon dioxide were identified by others. What Lavoisier did was to reinterpret how these elements interact. Contemporary chemists invoked a substance called “phlogiston” to explain why things burn or rust; it was thought that phlogiston was given off when a substance burned. In 1778, Lavoisier proposed that oxygen was the key element; things burn by taking on oxygen, not by giving off phlogiston. Rusting is just a slower “oxidation” of an element.

The oxygen theory of combustion turned out to have much more explanatory power that the phlogiston theory, especially since it explained why substances gain weight when they oxidize. Lavoisier later set down the first modern list of elements, and he also reformed chemical nomenclature, dumping the colorful alchemical language of “flowers of sulfur” and “sugar of lead” in favor of carbonates and oxides and adjectives like sulfuric and nitrous. His collaborator in much of his work was his wife, Marie-Anne Pierrette Paulze, who also illustrated most of Lavoisier’s scientific publications. It is sad that she had to witness Lavoisier’s final fate. Lavoisier was a member of the Ferme-Générale, a tax collection agency, and he was arrested along with the other administrators during the Reign of Terror and executed by guillotine on May 8, 1794, at age 50. As a countryman said at the time, “It took only a moment to cause this head to fall, and a hundred years will not suffice to produce its like.”

The double portrait of Antoine and Marie-Anne above was painted by the great Jacques-Louis David in 1788, and you can see it in the Metropolitan Museum of Art in New York City. The other image shows a reconstruction of Lavoisier’s laboratory at the Musée des arts et métiers in Paris.

We have nearly all of the works of Lavoisier, as well as numerous translations, in our History of Science Collection.

Dr. William B. Ashworth, Jr., Consultant for the History of Science, Linda Hall Library and Associate Professor, Department of History, University of Missouri-Kansas City

Let’s play an ochem game. :D

I was looking through old ochem notes to refresh a bit before the school year starts, and I found this one exam problem. Nobody in our class got it right, and it took a day or two and the combined efforts of a few of my friends and I to figure it out.

Cookie points to whoever can name the product and draw a mechanism! :D

EDIT: The reaction is acid-catalyzed! Completely forgot about that. Oops.

Metabolic processes that underpin life on Earth have arisen spontaneously outside of cells. The serendipitous finding that metabolism – the cascade of reactions in all cells that provides them with the raw materials they need to survive – can happen in such simple conditions provides fresh insights into how the first life formed. It also suggests that the complex processes needed for life may have surprisingly humble origins.

"People have said that these pathways look so complex they couldn’t form by environmental chemistry alone," says Markus Ralser at the University of Cambridge who supervised the research.

But his findings suggest that many of these reactions could have occurred spontaneously in Earth’s early oceans, catalysed by metal ions rather than the enzymes that drive them in cells today.

The origin of metabolism is a major gap in our understanding of the emergence of life. “If you look at many different organisms from around the world, this network of reactions always looks very similar, suggesting that it must have come into place very early on in evolution, but no one knew precisely when or how,” says Ralser.

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