Discovery Labs

A reaction commonly developed in the discovery lab is removing a Boc group from an amine using trifluoroacetic acid (TEA). Because TEA is highly corrosive, difficult to contain and recover (bp 72°C), and poses incineration problems due to the generation of HE, alternative conditions are usually explored for scale-up. Strong acids used instead of TEA include HCl, H2SO4, methanesulfonic acid, and toluenesulfonic acid... 

Take a moment to look around you. Where did all the stuff you see come from All the stuff in the universe is made from building blocks formed in stars such as the ones shown in the photo on the opposite page. And, as you learned in the DISCOVERY LAB, this stuff changes form. 

Consider the quarter and the piece of foam in Figure 2-4. In this case, the objects have the same mass. Because the density of the quarter is much greater than the density of the foam, the quarter occupies a much smaller space. How does density explain what you observed in the DISCOVERY LAB ... 

Although three suhatomic particles had heen discovered hy the early-1900s, the quest to understand the atom and its structure had really just begun. That quest continues in this chapter, as scientists pursued an understanding of how electrons were arranged within atoms. Perform the DISCOVERY LAB on this page to better understand the difficulties scientists faced in researching the unseen atom. 

Do you know that the foods you eat, the fibers in your clothes, and the plastic in your CDs have something in common Foods, fibers, and plastic are produced when the atoms in substances are rearranged to form different substances. Atoms are rearranged during the flash of lightning shown in the photo on the opposite page. They were also rearranged when you dropped the effervescent tablet into the beaker of water and indicator in the DISCOVERY LAB. 

Chemists also need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance. As you know, atoms and molecules are extremely small. There are so many of them in even the smallest sample that it s impossible to actually count them. That s why chemists created their own counting unit called the mole. In the DISCOVERY LAB, you found that a mole of paper clips is an enormous number of items. 

It is difficult to remove dirt from skin or clothing using only water. Because dirt particles cannot penetrate the surface of the water drops, the water cannot remove the dirt. What happened when you added a drop of detergent to the heaker in the DISCOVERY LAB Soaps and detergents decrease the surface tension of water hy disruphng the hydrogen bonds between water molecules. When the bonds are broken, the water spreads out. Compounds that lower the surface tension of water are called surface active agents or surfactants. 

Gas particles are much smaller than the distances between them. You saw in the DISCOVERY LAB that gas has volume. However, the kinetic theory assumes that gas particles themselves have virtually no volume. 

As you observed in the DISCOVERY LAB at the beginning of this chapter, some solutions release energy as they form, whereas others absorb energy during formation. For example, after ammonium nitrate dissolves in water, its container feels cool. In contrast, after calcium chloride dissolves in water, its container feels warm. You will learn more about the heat of solution in the next chapter. 

One of the most spectacular chemical reactions, the one between liquid hydrogen and liquid oxygen, provides the energy to launch rockets into space as shown on the opposite page. This reaction is fast and exothermic. Yet other reactions and processes you re familiar with, such as the hardening of concrete or the formation of fossil fuels, occur at considerahly slower rates. The DISCOVERY LAB for this chapter emphasized that the speed at which a reaction occurs can vary if other substances are introduced into the reaction. In this section, you ll learn about a model that scientists use to describe and calculate the rates at which chemical reactions occur. 

When you get off a whirling amusement park ride, you probably pause a minute to get your equilibrium. If so, you are talking about getting your balance back after the ride exerted rapidly changing forces on you. But soon you are balanced steadily on your feet once more. Often, chemical reactions also reach a point of balance or equilibrium. The DISCOVERY LAB is an analogy for chemical equilibrium. You found that a point of balance was reached in the transfer of water from the beaker to the graduated cylinder and from the graduated cylinder to the beaker. 

When ants sense danger to the ant colony, they emit a substance called formic acid that alerts the entire colony. Acids in rainwater hollow out enormous limestone caverns and destroy valuable buildings and statues. Acids flavor many of the beverages and foods you like, and it s an acid in your stomach that helps digest what you eat. Bases also play a role in your life. The soap you use and the antacid tablet you may take for an upset stomach are bases. Perhaps you have already concluded that the household products you used in the DISCOVERY LAB are acids and bases. 

The litmus in litmus paper is one of the dyes commonly used to distinguish solutions of acids and bases, as shown in Figure 19-1. Aqueous solutions of acids cause blue litmus paper to turn pink. Aqueous solutions of bases cause red litmus paper to turn blue. With this information you can now identify the two groups of household products you used in the DISCOVERY LAB. 

In Chapter 10, you learned that a chemical reaction can usually be classified as one of five types—synthesis, decomposition, combustion, single-replacement, or double-replacement. In this chapter, you ll investigate a special characteristic of many of these reactions— the ability of elements to gain or lose electrons when they react with other elements. You experimented with this characteristic when you did the DISCOVERY LAB. 

In Chapter 20, you learned that all redox reactions involve a transfer of electrons from the species that is oxidized to the species that is reduced. The DISCOVERY LAB illustrates the simple redox reaction in which zinc atoms are oxidized to form Zn + ions. The two electrons donated from each zinc atom are accepted by a Cu + ion, which changes to an atom of copper metal. The following net ionic equation illustrates the electron transfer that occurs. 

A visitor to the discovery labs of any pharmaceuticals company will note the importance attached to biology and biochemistry. Richard Maurer and Chris Reynolds show us how seriously modelling is taken in the world of biology. 

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