Introduction to Organic Chemistry
(making n-butyl acetate)

    The first two things you will notice in moving from inorganic chemistry over to organic chemistry are (a) the compounds are much larger, but (b) only a few elements are usually used. One of nature's beauties with regard to carbon is that it forms long chains. Only one other element also does so - silicon - but nowhere nearly as many types. It is only within the realm of carbon's complexity that life and all its complexity can exist.

    Today you will see on the side-shelf a collection of bottles of different alcohols. You are familiar with a few - methanol, ethanol, n-propanol (1-propanol) and isopropanol (2-propanol). You will also see n-butanol, isobutanol and n-pentanol (n-amylol), and others.

    Nearby you will see a bottle of what is called acetic anhydride. "Anhydrides" are chemicals from which a water molecule has been subtracted from two molecules. One example is of phosphoric anhydride or "pyrophosphate". Notice in this dehydration reaction how a water molecule is removed - the H from one molecule and an OH from the other:

    That was with an inorganic acid making its anhydride. Let us now consider a simple organic acid with which you have familiarity - acetic acid (the essence of vinegar). Here is how it is coverted to acetic anhydride:

    The acid anhydrides would "love" to react with water to get back to their normal state. You can try it by adding a few drops of acetic anhydride to about 1 cm water in a test tube and heating it (E_act, remember!). To heat these flammable substances, DO NOT USE A FLAME! Instead set up an aluminum container on an electrical heater, set the test tube in the boiling water for 15 seconds or so. Do you smell the acetic acid that is formed? (Vinegar!) Here's what happened:

    Now let's not use water, but rather some of its alcoholic analogs. Put 4 drops of each alcohol into appropriately marked test tubes. Sniff them. Next add 8 drops of acetic anhydride to each tube; heat; cool and sniff. Notice anything different?

    Here's generally what happens. In the following "R" indicates the organic moiety that is attached to the alcoholic OH group.

    What you get in the first reaction are an acetylated alcohol (e.g.: n-propylacetate) and rather stinky acetic acid. You can eliminate the smell of the acetic acid by neutralizing it with a strong base (ions are not normally odiforous). Thus, once you have performed the first reaction, heat with some water to eliminate any excess acetic anhydride, and then add a drop of phenolphthalein, followed by enough NaOH to make the solution pink. Then sniff!