Simple and common drug preparation

Synthesis of Aspirin and Oil of Wintergreen


Cautions
Acetic Anhydride – corrosive and a lachrymator – all transfers should be done in the vented fume hood
Methanol, Ethanol – flammable and highly toxic
Salicylic Acid – toxic and irritant
Sulfuric Acid, Phosphoric Acid – highly toxic, corrosive, and an oxidant
Purpose
To synthesize acetylsalicylic acid (aspirin) and methyl salicylate (oil of wintergreen) to review the concepts of
theoretical and percent yields.
Introduction
Organic chemistry plays a vital part in the chemical industry as it is used in making petroleum products,
polymers/plastics, pharmaceuticals, and health and beauty aids. Many everyday products are primarily comprised of
organic molecules.
Organic molecules are classified by how different atoms are arranged in their structures. For examples, all
alcohols contain a carbon atom bound to an OH group; for example, methyl alcohol is CH3OH. Aspirin and oil of
wintergreen are esters. An ester is an organic compound that contains the molecular
connectivity shown in Figure 1. Esters tend to be volatile and have pleasant odors. This
class of organic molecules is responsible for the inviting aromas and fragrances of fruits and
flowers. The cosmetic industry has exploited the use of esters in the production of cosmetics
and perfumes. The food and pharmaceutical industry also use esters in the form of flavoring
agents in solid and liquid products.
Aspirin is the most widely used medical compound in the world. Aspirin, known chemically as acetylsalicylic acid,
is a white solid that has a very low solubility in water (0.25 g in 100 ml of water). A regular strength aspirin tablet contains
325 mg of acetylsalicylic acid held together with an inert binder such as starch. Aspirin is derived from salicylic acid which
occurs naturally in the bark of willow trees. This reaction is shown in Reaction 1. Both aspirin and salicylic acid are
important due to their analgesic (pain reliever) and antipyretic (fever reducer) properties. Aspirin is less acidic than
salicylic acid which helps in the reducing the number of stomach, mouth, and mucus membrane irritations. Therefore, it is
used instead of salicylic acid. However, some people find that aspirin is still too acidic and may opt for some of the less
acidic alternatives such as Tylenol (acetaminophen) or Advil (ibuprofen). It is believed that all of these compounds act
within the human body to inhibit the production of prostaglandins, which are used in the perception of pain