Aromatic aldehydes are organic chemical compounds that contain a carbon hydroxide radical or group, CHO, and are used as precursor chemicals in the pharmaceutical and plastics industries. The simplest of aromatic aldehydes is benzaldehyde, C6H5CHO, which is an almond extract that is used as a flavoring, and as an ingredient in some dye and plastics production. Many commercial preparations of these aldehydes exist for a variety of industrial uses. Tolualdehyde or p-tolualdehyde (PTAL), is used as a intermediate compound in agricultural and pharmaceutical products, p-ethylbenzaldehyde (EBAL) is used as a flavor and fragrance, and p-isobutylbenzaldehyde (IBBAL) is an additive for plastic resins. The smallest examples of aromatic aldehydes such as benzaldehyde are soluble in water, though most of them also tend to be very flammable.
Aldehydes and ketones are related compounds where an aldehyde contains at least one hydrogen atom attached to a carbonyl group of a carbon-oxygen bond. A ketone contains two alkyl groups, CnH, attached to the carbon atom of the carbonyl group. The two most commonly used aromatic aldehydes and aromatic ketones are formaldehyde and acetone, respectively. Formaldehyde is a widely used preservative and acetone is the main ingredient in many solvents. As of 2009, approximately 6,000,000,000 pounds (2,721,554,220 kilograms) of formaldehyde were created annually in industry and 11,243,575,400 pounds (5,100,000,000 kilograms) of acetone.
There are literally hundreds of different varieties of aromatic aldehydes and ketones manufactured by the chemical industry that are used to produce plastics and dyes. While they are commonly used to synthesize other chemicals for use in agriculture and pharmaceuticals as well, their most important consumer application, aside from formaldehyde and acetone production is as perfumes and flavoring agents. Several widely used examples of these aldehydes are obtained as natural derivatives, with benzaldehyde being derived from almonds, cinnamaldehyde from cinnamon, and carvone from caraway seeds as a spearmint flavor. Vanillin is another example that is obtained from vanilla beans, or can be prepared synthetically, and is known commercially as 3-methoxy-4-hydroxybenzaldehyde, (CH3O)(OH)C6H3CHO. Aromatic esters are related compounds with hydroxyl alcohol groups, which are also used as lighter weight fragrances in consumer products.
Esters, ketones, and aromatic aldehydes also have chemical components that make them important in human biological functions. Carbohydrates such as sugars and starches are based on compounds that contain ester hydroxyl groups, or aldehydes and ketones. Steroids produced by the human body, such as testosterone, cortisone, and progesterone, are ketones as well, and retinal is an aldehyde that is essential for human vision.