Common Scents Molecules

Here's an observation game for you to play with some molecular structures from very smelly molecules (that can be a good thing or a very BAD thing)!

Here's the first set! (C means carbon, H means hydrogen, S means sulfur):

Do molecules that contain sulfur seem to smell nice? Of course, these are only a few of the millions of molecules that can contain sulfur, but frankly, most of them are pretty stinky!

Now look at the second group! (C means carbon, H means hydrogen, N means nitrogen):

Whoa! These are worse than the sulfur-containing molecules! In fact, most of the world's very worst-smelling molecules contain nitrogen. There's even one called "putrescene"! However, there are also many, many perfectly odor-free nitrogen-containing molecules!

Let's do some nicer-smelling examples (C means carbon, H means hydrogen, O means oxygen):

Now we're talking! These are odors that we don't mind sniffing! What features do you observe in common? See that group with an O next to a =O? The atom without a label is a carbon. That's called an ester group, and esters tend to have sweet, pleasant odors. Find the ester group in each molecule.

More nice molecules:

These are a group of molecules called terpenes. They have that hexagon thing at the top (which is sometimes broken, with only 5 carbons), and that funny fishtail part at the bottom. Terpenes tend to have sharp, but pleasant, odors. Notice that there are different things hanging off the rin in different places, and these are what make each molecule smell different.

Here's the last set! (C means carbon, H means hydrogen, O means oxygen):

All of these molecules are aldehydes, because they all have the HC=O part. See if you can find this aldehyde group in each example.

Now, please understand that natural scents usually have lots of molecules in them, not just one. However, in all of these examples, if you smelled this molecule, you would know immediately what it came from. The smell wouldn't be exactly like the natural scent, but you could recognize it.

One final comment - earlier this month, we talked about how the receptors in the nose reacted with the odor molecules, letting you smell them? Well, these are examples of those odor molecules. Now here's the cool thing - your nose's receptors can tell that these molecules have different sizes and shapes, and that's how you can tell smells apart! The receptors send slightly different signals to your brain, which knows that you should identify one kind of signal with bananas, and another kind with poop! And that's a very good thing!

What's That Smell??

You've undoubtedly noticed that some vegetables are smellier than others. Corn, carrots, lettuce, green beans - they don't have much odor to them. But what about onions, garlic, and cabbage? Whew! These vegetables can make your eyes water, especially when they're cooking. Why does that happen?

All of these vegetables contain the element sulfur. In its pure form, sulfur is a light yellow powder that doesn't have much of an odor. But if you combine it with some carbon, hydrogen, and maybe a little oxygen and/or nitrogen, you can make some of the stinkiest molecules on earth! These molecules evaporate into the air easily, which is why you can smell them. The good part is that, when you cook these vegetables, the smelly sulfur-containing molecules leave. That means that they're pretty stinky while they're cooking, but that they taste much different (and often better) when they're done.

Try cooking some cabbage to check this out. Take a head of raw cabbage and cut it in half (have an adult help). Smell and taste both halves - they should be the same. Now cut one half into small pieces and place the leaves into a saucepan with 1 cup of water. Boil uncovered for 20 minutes. How does the cooking cabbage make the room smell? When the cabbage is done, remove a piece and let it cool. Compare its taste and smell to that of the uncooked half. What do you notice?

The kitchen got pretty smelly while the cabbage was cooking. That's because the sulfur-containing molecules left the leaves and went into the air. But the cooked cabbage tasted and smelled quite different from the uncooked cabbage because all or most of the stinky molecules had evaporated!

Fun Facts 1

Here are some fun and interesting facts about chemical elements:

• There is more hydrogen (H, #1) in the universe than any other element. In fact, 88% of the atoms in the universe are H's! Most of them could be found in stars or in space.


• The thin wire filament in an incandescent light bulb is made of tungsten (W, #74). It glows bright white when electricity passes through it.


• The dark-gray mineral stibnite contains antimony (Sb, #51). In ancient times, it was ground up and used as mascara.


• Smoke detectors used in the home contain small amounts of the radioactive element americium (Am, #95). You should never take a smoke detector apart for this reason!


• Compounds that contain sulfur (S, #14) give onions and garlic their strong smells.


• The element nobelium (No, #102) is named after Alfred Nobel, who invented dynamite, then donated his money to create the Nobel Prizes, given for Peace, Literature, Medicine, Economics, Physics, and Chemistry. The winners of these prizes are named in early October, so listen for the announcement!


• The presence of a strontium (Sr, #38) compound gives red fireworks their color.


• Aluminum (Al, #13) was once more expensive than gold! In fact, the French emperor Napoleon III had special sets of aluminum forks, spoons, and knives made for his very special dinner guests! It wasn't until two chemists (in France and in the U.S.) discovered ways to produce aluminum cheaply that it became a commonly used metal.


• Very accurate atomic clocks are based on vibrations of the cesium (Cs, #55) atom.


• The upset-stomach reliever Pepto-Bismol contains the element bismuth (Bi, #83).