Polyamide Formation

Amide Formation

• Polyamides are condensation polymers produced through the reaction of di-acid chlorides with diamines.
• The repeating units in polyamides are held together by amide linkages.
• Three billion pounds of nylon and related polyamides are produced annually.
• Nylon is used in various applications, including home furnishings (e.g., carpet), textile fibers in clothing and tire cord, and minor uses such as fasteners, rope, parachutes, paintbrushes, electrical parts, medical tubing, and nylon sutures.

Naming Amides

• Use the carboxylic acid's name and drop the –ic ending (common name) or –oic ending (IUPAC name) and change to –amide.
• Use N to denote alkyl groups attached to the nitrogen atom.

Physical Properties of Amides

• Hydrogen bonding between unsubstituted amides causes them to have high melting points.
• Formamide is a liquid at room temperature.
• All other unsubstituted amides are solids at room temperature.
• Amides can form hydrogen bonds with water, making smaller amide molecules (less than 6 carbon atoms) rather water soluble.

Amide Reactions

• Amides are neither acidic nor basic.
• Amide hydrolysis is the reverse of amide formation; an amide is cleaved to produce a carboxylic acid and an amine or ammonia.
• Amide hydrolysis is a central reaction in the digestion of proteins and the breakdown of proteins within cells.
• In the body, this hydrolysis is catalyzed by enzymes.
• The products of an amide hydrolysis depend on whether the reaction occurs in acidic or basic conditions.
• One hydrolysis product must always be in the form of a salt.

Amides in Medicine

• Amides are used in medicine.

Amines

• Amines behave as weak bases and form salts when they react with acids such as HCl.
• Amines can form salts with sulfuric, nitric, phosphoric, and carboxylic acids as well.
• Amine salts can be converted back to amine form by adding a strong base.
• The form in which amines occur in solutions is pH dependent, just as is the case for carboxylic acids.

Amine Neurotransmitters

• Neurotransmitters are substances that act as chemical bridges between nerve cells.
• Examples of important amine neurotransmitters include:
  • Acetylcholine
  • Dopamine
  • Norepinephrine
  • Serotonin

Other Biologically Important Amines

• Epinephrine (adrenaline) is a hormone that increases blood glucose levels for energy.
• Amphetamines are nervous system stimulants, similar in structure to epinephrine.
• Alkaloids are a class of nitrogen-containing organic compounds obtained from plants.
• Examples of alkaloids include:
  • Nicotine
  • Caffeine
  • Quinine
  • Opium

Amine Reactions

• Amines react with acid chlorides or acid anhydrides to form amides.
• The amide linkage can be thought of as separating an ammonia or amine portion and a portion derived from a carboxylic acid.
• Primary and secondary amines can form amides.
• Tertiary amines do not react to form amides.

Naming Amines

• Common naming: alphabetically link the names of the alkyl or aromatic groups bonded to the nitrogen and attach the suffix –amine.
• IUPAC naming: name the longest carbon chain, replace the –e ending with -amine, and use the prefix N to identify the Nitrogen substituents.

Physical Properties of Amines

• The N-H bond is not quite as polar as the O-H bond.
• Primary and secondary amines can form hydrogen bonds between molecules.
• The hydrogen bonds are not as strong as those of alcohols, so amine boiling points are somewhat lower than those of alcohols.
• Simple, low molecular weight amines are gases at room temperature.
• Heavier, more complex compounds are liquids or solids.
• Amines can hydrogen bond with water, making smaller amine molecules (less than 6 carbon atoms) usually water soluble.
• Low molecular weight amines have a sharp, penetrating odor similar to that of ammonia.
• Some amines are partially responsible for the odor of decaying animal tissue.

This quiz covers the reaction of di-acid chlorides with diamines to form polyamides, a type of condensation polymer. It also explores the uses of nylon and related polyamides.