16-1 Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping, and Caret 4 th ed Chapter 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Power Point to Accompany

16-2 Amines have these structures: RNH 2, R 2 NH, R 3 N (R is aliphatic or aromatic) Amines, like alcohols, can be put into classes. Class depends on the number of carbons directly bonded to the nitrogen atom: a primary amine has one bond, a secondary two, etc. RNH 2, R 2 NH, R 3 N 1 o 2 o 3 o 16.1 Amines

16-3 Amines: Physical properties Most amines up to 5 or 6 carbons are water soluble due to hydrogen bonding with the water molecule.

16-4 Amines: Physical properties-2 Amines have boiling points between alkanes and alcohols. They hydrogen bond but not as strongly as alcohols. Tertiary amines cannot hydrogen bond to each other and boil lower then 1 o or 2 o of similar molecular weight. C 4 H 8 (58), bp 0 o C C 3 H 7 NH 2 (59), bp 48 o C C 3 H 7 OH (60), bp 97 o C

16-5 Amine names: Chem Abstracts Primary aliphatic amines are named by dropping the final –e of the parent name and adding the suffix -amine. Name: CH 3 CH 2 NH 2 ethanamine

16-6 Amine names: Chem Abstracts-2 The prefix N-alkyl is added to the name of the parent for 2 o and 3 o amines. Name: N-ethylethanamine

16-7 Amine names: IUPAC For primary amines, the prefix amino and a number designates the position of the amino group on an alkane parent chain. A substituent on the N uses the –N prefix as with the Chem Abstracts system. 2-aminopropane N-methyl-2-aminopropane

16-8 Amine names: Common Names Name the alkyl groups attached to the N in alphabetical order and add –amine. The name is continuous, no spaces between groups. Name: Methylsec-butylamine

16-9 Amine names Aromatic amines are named as N-substituted derivatives of aniline. (See aromatics) Name a) and b): a) m-nitroaniline b) N-methylaniline

16-10 Reactions of Amines: Preparation Aliphatic amines are prepared via reduction of amides. E. g. Aromatic amines are prepared via reduction of nitro compounds. E. g.

16-11 Reactions of Amines: Basicity Amines are weak bases. They accept protons from water making solutions basic.

16-12 Reactions of Amines: Neutralization Amines form salts by accepting a proton from strong mineral acids. Converting amines to salts often makes insoluble amines soluble!!!!! Name amine salts by replacing the suffix –amine with ammonium and the name of the anion. E. g. propylammonium chloride

16-13 Reactions of Amine Salts: Neutralization Amine salts revert to the amine (donate a proton) in strong base.

16-14 Amine Reactions: “Quats” 3 o amines react with alkyl chlorides to give quaternary ammonium salts which are very important in biochemistry.

16-15 “Quats” cont. Benzalkonium chloride (Zephiran TM ) and choline are important examples.

Heterocyclic Amines Heterocyclic amines have at least one nitrogen in the ring. MANY are physiologically active and many are critical in biochemistry.

16-17 Examples of Heterocyclic Amines

16-18 Examples of Heterocyclic Amines-2

Amides Most amides are solids at room temperature due to internal hydrogen bonding. They are not bases. A resonance structure shows why the N lone pair is unavailable to accept a proton.

16-20 Amide Names Names are derived from the acid. Remove –ic acid (common) or –oic acid (IUPAC) and replace with –amide. Nitrogen substituents are prefixed to the name and indicated by N. ethanamide or acetamide N-methylpropanamide

16-21 Preparation of Amides 1 o and 2 o amines react with acid chlorides to give amides. The acid chloride transfers its acyl group to the N of the amine.

16-22 Preparation of Amides-2 1 o and 2 o amines react with acid anhydrides to give amides. E. g. with acetic anhydride.

16-23 Amino Acids and Proteins An alpha amino acid is a carboxylic acid with an amino group on the carbon alpha to the carboxylic acid. The alpha carbon also has an R group side chain except for glycine which has two Hs. Generic amino acid at physiological pH.  C

16-24 Peptides A peptide is a polymer of about amino acids linked by the peptide(amide) bond. As the amino group and the carboxyl group link, water is lost.

16-25 Hydrolysis of Amides a) Amides hydrolyze with acid to give the carboxylic acid and the amine salt. b) Amides hydrolyze with base to give the carboxylic acid salt and the amine.

Amino Acids and Protein Synthesis  -amino acids are attached to transfer RNA molecules (t-RNA). The acyl group ( and the amino acid) are transferred to the nitrogen of another amino acid to form a peptide (amide) bond. Aminoacyl group from amino acid

Neurotransmitters Neurotransmitters carry signals from a nerve cell to a target They can be excitatory or inhibitory. All contain nitrogen. catecholamines A deficiency in dopamine results in Parkinson’s disease. Too much is associated with schizophrenia. It is also associated with the “high” of drugs.

16-28 Neurotransmitters-cont. Catecholamines-cont. Epinephrine (adrenaline) and norepinephrine are involved in the fight or flight response. Serotonin A deficiency is associated with depression, bulemia and anorexia nervosa. It also affects pain perception, thermoregulation, and sleep.

16-29 Neurotransmitters-cont. Histamine is released during an allergic response. Benadryl is a typical antihistamine used for colds and other allergic responses. Acetylcholine functions at the neuromuscular junction to cause muscles to contract.

16-30 Amines and Amides The End