18.5 Amides Tylenol, an aspirin substitute, contains acetaminophen. Acetaminophen is an amide; it acts to reduce fever and pain; however, it has little anti-inflammatory effect. Learning Goal Draw the amide product from amidation, and give the IUPAC and common names.

Preparation of Amides Amides are derivatives of carboxylic acids in which a nitrogen group (—NH2) of a primary or secondary amine replaces the hydroxyl (—OH) group of carboxylic acids. Core Chemistry Skill Forming Amides

Preparation of Amides Amides are produced in a reaction called amidation or condensation. when a carboxylic acid reacts with ammonia or a primary or secondary amine and heat. Amide production is accompanied by the production of water.

Study Check Predict the products of the following amidation reaction:

Solution Predict the products of the following amidation reaction:

Naming Amides In both the common and IUPAC names, amides are named by dropping the oic acid (IUPAC) or ic acid (common) from the carboxylic acid name and adding the suffix amide. Alkyl groups attached to the nitrogen of an amide are named with the prefix N followed by the alkyl name.

Guide to Naming Amides

Naming Amides Give the IUPAC name for the following amide: STEP 1 Replace oic acid (IUPAC) or ic acid common) in the carboxyl name with amide. butanamide ANALYZE Given Need THE amide IUPAC name PROBLEM

Naming Amides Give the IUPAC name for the following amide: STEP 2 Name each substituent on the N atom using the prefix N and the alkyl name. N-methylbutanamide

Study Check Give the IUPAC and common names for the following amides: A. B.

Study Check Give the IUPAC and common names for the following amides: A. B. ethanamide (IUPAC) acetamide (common) N-ethylpropanamide (IUPAC) N-ethylpropionamide (common)

Physical Properties of Amides Amides do not have the properties of bases seen in amines. Only methanamide is a liquid at room temperature, while other amides are solids. Primary (1°) amides have the highest melting points because the the —NH2 group can form the most hydrogen bonds. Melting points of the secondary (2°) amides are lower because they form fewer hydrogen bonds. Tertiary (3°) amides cannot form hydrogen bonds; they have the lowest melting points (see Table 18.3).

H-Bonding in 1° Amides Primary (1°) amides, can form hydrogen bonds with the –NH2 group of other amides hydrogen bonds with water molecules making them soluble in water as long as they have less than five carbons

H-Bonding in 2° Amides Secondary (2°) amides have lower melting points because they form fewer hydrogen bonds with other amides. form hydrogen bonds with water molecules, making them soluble in water as long as they have fewer than five carbons.

H-Bonding in 3° Amides Tertiary (3°) amides have the lowest melting points because they form the fewest hydrogen bonds. can only form one hydrogen bond with H2O.

Chemistry Link to Health: Amides and Medicine Urea is the simplest natural amide. the end product of protein metabolism in the body. excreted in the urine. If the kidneys malfunction, urea is not removed and builds to a toxic level, a condition called uremia.

Chemistry Link to Health: Amides and Medicine Aspirin substitutes contain phenacetin and acetaminophen. act to reduce fever and pain but have little anti-inflammatory effect.

Chemistry Link to Health: Amides and Medicine Many barbituates are cyclic amides of barbituric acid. act as sedatives in small doses or sleep inducers in large doses. are habit forming. Barbiturate drugs include phenobarbital (Luminal) and pentobarbital (Nembutal).