Читать книгу Biochemistry For Dummies - John Moore T., Richard Langley H., John T. Moore - Страница 45

Many functional groups contain oxygen, including alcohols, ethers, aldehydes, and ketones. You encounter many of these oxygen-containing functional groups when you study carbohydrates (one of our favorite things). In carbohydrates, many times the ether groups are referred to as glycoside linkages (more on carbohydrates in Chapter 7). In addition, carboxylic acids and esters are important functional groups that appear as fatty acids and in fats and oils.

Alcohols and ethers contain only singly bonded oxygen atoms. An alcohol group attached to an aromatic ring is a phenol. Aldehyde and ketone functional groups contain only doubly bonded oxygen atoms. Carboxylic acids and esters contain both singly and doubly bonded oxygen atoms. The combination of a carbon atom connected to an oxygen atom by a double bond is a carbonyl group.

Sulfur, the element immediately below oxygen on the periodic table, may replace oxygen in both alcohols and ethers to give thiols (mercaptans) and thioethers. Many of these sulfur-containing compounds really stink! Sulfur may also form a disulfide, which has a bond between two sulfur atoms. Figure 3-3 illustrates these compounds.

FIGURE 3-3: Oxygen- and sulfur-containing functional groups.