Amines and Amides

Amines and Amides Amines and Amides both contain nitrogen (N).

Amine Classification Classified as primary, secondary, or tertiary based on the number of alkyl groups attached to the nitrogen atom.

Naming Primary Amines Use the alkyl chain prefix, drop the -e and add the –amine suffix to represent the nitrogen containing functional group. The simplest amine structure is CH3NH2. The name of this compound is methanamine. (Alternatives are methylamine or aminomethane)

Naming Secondary and Tertiary Amines The longest alkyl chain is named by dropping the –e of the alkane group and adding the -amine suffix. The carbon attached to the nitrogen of the longest chain is designated carbon 1. The locator, N, is then used to indicate the attachment of additional chains to the nitrogen atom (similar to how a number is used to indicate the attachment on a carbon atom). Example: An amine with an ethyl, propyl and butyl group, each bonded to the nitrogen atom at carbon 1 is named:

Compounds with Multiple Amino Groups Compounds with more than one amino group are possible. Example: The molecule below contains two nitrogen atoms (one at each end). The -diamine suffix is used to represent two amino groups. IUPAC name: pentane-1,5-diamine

Naming Amines as Branches Sometimes it is necessary to name the amine group as a branch. Carboxylic acids take precedence over all functional groups In this case, the prefix –amino is used. IUPAC Name: 5-aminopentanoic acid

Amines attached to Benzene The root name for an amine attached to a benzene ring is aniline.

Practice: Naming Amines Name each of the following amines: CH3CH2CH2NH2 d) CH3NHCH3 e)

Practice: Drawing Amines Draw the structural formula for each: N-ethylethanamine d) 5-methylhexan-2-amine butanamine N-propylpentan-2-amine

Properties of Amines Nitrogen is more electronegative than Carbon or Hydrogen, but less electronegative than Oxygen N-C and N-H bonds are considered polar, but have weaker dipole-dipole intermolecular forces than C-O and O-H bonds Therefore, overall amines are less polar than carboxylic acids and alcohols but more polar than alkanes

Properties of Amines cont’d.. Comparing Primary, Secondary and Tertiary Amines Primary amines can form 2 hydrogen bonds, secondary amines can form 1 hydrogen bond and tertiary amines cannot hydrogen bond As a result, primary amines have the highest boiling points and tertiary amines have the lowest boiling points

Amides Are derivatives of carboxylic acids. The carbonyl group is joined by a nitrogen group (-NH2) instead of the –OH group from carboxylic acids. Carboxylic acids react with alcohols to form esters. Carboxylic acids react with ammonia, primary amines, and secondary amines to form amides.

Naming Amides Is similar to naming esters. Three parts: First part comes from the amine. Second part comes from the acid. Third part is the suffix –amide. Example: The reaction of methanamine and butanoic acid will produce the amide: N-methylbutanamide.

Practice: Naming and Drawing Amides Name each of the following amides: Draw a structural diagram for: 3-chloro-4-methylpentanamide

Properties of Amides Amides contain a carbonyl group (C=O) and have the N-C and N-H bonds that contribute to an overall very polar molecule As a result, amides are the most polar functional group and have high boiling and melting points Since, amides have the potential for hydrogen bonding, they have high boiling and melting points Smaller amides are soluble in water. As the length of the amide chain increases, solubility decreases.

Homework pg. 58 # 1-2 pg. 60 # 1-2 pg. 62 # 1-3