Chapter 21 Laboratory: Synthesis of Useful Compounds 373

Laboratory:

Synthesis of Useful Compounds

Chemical reactions are often themselves interesting, but most chemical reactions have the

practical goal of synthesizing some useful compound. With the exception of purely natural

products, nearly every material you come into contact with in your daily life is the product

of a chemical synthesis. Those products were first synthesized on a small scale by chemists

in laboratories, and later produced on an industrial scale using processes designed by

chemists and chemical engineers.

In choosing the sessions for this chapter, I was faced with an embarrassment of riches.

I could have chosen to synthesize any of literally thousands of common, everyday

compounds, from soaps to plastics, dyes and pigments, common drugs such as aspirin,

and... well, you get the idea. From that huge list of possibilities, I chose two representative

syntheses.

In the first lab session, we synthesize methyl salicylate from aspirin and methanol. Methyl

salicylate, better known as synthetic oil of wintergreen, is an interesting compound. Although

it is toxic if a large quantity is ingested, it is commonly used to provide wintergreen flavoring

in candies and other foods. It’s also the primary active ingredient in many muscle rubs and

balms, giving them their minty odor.

In the second lab session, we begin by synthesizing the copper-ammonia coordination

compound tetraamminecopper(II) hydroxide, [Cu(NH 3 ) 4 ](OH) 2 ), better known as

Schweizer’s Reagent. That compound has the interesting property of being a solvent for

cellulose. We’ll use the Schweizer’s Reagent we synthesize to dissolve some paper and then

use that cellulose solution to produce rayon, which was the first semisynthetic fabric.

21

dAR. Rm y CHERvENAk CommENTS:

When a pathogen infects one part of the plant, the

tissue under attack notifies surrounding healthy plants

of impending danger. The molecular messenger is

methyl salicylate.