CH103 Chapter 16 Lecture Notes (1) PDF

 16.1 Amines C, H, and O are the three most common elements in organic g compounds. Nitrogen is the fourth most common element of organic compounds. Wide Wid didistribution t ib ti off amines i in...

 16.1 Amines C, H, and O are the three most common elements in organic g compounds. Nitrogen is the fourth most common element of organic compounds. Wide Wid didistribution t ib ti off amines i in i th the bi biological l i l world. ld The most important chemical property of amines is their basicity. basicity The functional group of an amine is an amino group ((NH2, RNH2, R2NH,, or R3N g group)—a p) nitrogen g atom bonded to one, two, or three carbon atoms.  Amine Types Classification of amines: In a primary (1°) amine, nitrogen is bonded to two hydrogens and one carbon group. group In a secondary (2°) amine, it is bonded to one hydrogen and two carbon groups. In a tertiary (3°) amine, it is bonded to three carbon groups.  Amine Types H N R Primary: One R group attached to N 1o H H N R Secondary: Two R groups attached to N R 2o R N R Tertiary: Three R groups attached to N 3o R Aliphatic or Aromatic Amines Amines are further classified as aliphatic or aromatic. In an aliphatic amine, all carbon atoms bonded to nitrogen are derived from alkyl groups. In an aromatic amine,, one or more of the groups g p bonded to nitrogen are aryl groups.  Heterocyclic Amines In a heterocyclic amine, the nitrogen atom is part of a ring. When the ring is saturated, the amine is classified as a heterocyclic aliphatic amine. When the nitrogen is part of an aromatic ring the amine is classified as a heterocyclic aromatic amine. i  Heterocyclic Amines Heterocyclic aromatic amines are pyridine and pyrimidine, in which nitrogen atoms replace first one and then two CH groups of a benzene ring. Pyrimidine and purine serve as the building blocks for the amine bases of DNA and RNA. RNA 16.1 Nomenclature of Amines IUPAC names for aliphatic amines are derived just as they are for alcohols. The final -e of the parent alkane is dropped and replaced by -amine. Indicate the location of the amino group on the parent chain by a number.  Nomenclature of Amines The simplest aromatic amine is aniline (common name) C6H5NH2. Its simple derivatives are named using numbers to locate substituents or using the locators ortho (o), (o) meta (m), (m) and para (p). (p) Derivatives of aniline: i.e. toluidine for a methyl-substituted aniline. aniline  Nomenclature of Amines Unsymmetrical secondary and tertiary amines are commonly named as N-substituted primary amines. The largest group bonded to nitrogen is taken as the parent amine. amine The smaller groups bonded to nitrogen are named, and their locations are indicated by the prefix N (indicating that they are bonded to nitrogen).  Nomenclature of Amines Common names: Common names for most aliphatic amines list the groups bonded to nitrogen in alphabetical order in one word ending in the suffix –amine.  16.3 Physical Properties of Amines Like ammonia, low-molecular-weight amines have very y sharp, penetrating g odors. Trimethylamine - smells of rotting fish. Amines A i are polar l compounds. d Primary and secondary amines associate by intermolecular hydrogen bonding. Tertiaryy amines do not have a hydrogen bonded to nitrogen and, therefore, do not form hydrogen bonds with one another. 16.3 Physical Properties of Amines All classes of amines form hydrogen bonds with water and are more soluble in water than are hydrocarbons of comparable molecular weight. Most low-molecular-weight amines are completely soluble in water. Higher-molecular-weight amines are only moderately soluble in water or are insoluble.  16.4 Basicity of Amines Like ammonia (NH3), amines are weak bases, and aqueous solutions of amines are basic. Aliphatic Ali h ti amines i are stronger t bases b than th aromatic ti amines. Acid–base reaction between an amine and water Proton-transfer reaction Amines act as Lewis Bases  Basicity of Amines Aliphatic amines are stronger bases than aromatic amines. Select the stronger base in the pair of amines. Morpholine (B), a 2° aliphatic li h i amine, i i the is h stronger base. Pyridine (A) (A), a heterocyclic aromatic amine, is the weaker base.  Basicity of Amines Select the stronger base in the pair of amines. Aliphatic amines are stronger bases than heterocyclic amines. Aliphatic amines are stronger bases than aromatic amines.  16.5 Characteristic Reactions of Amines All amines, whether soluble or insoluble in water, react with strong g acids to form water-soluble salts. We can use this property to separate water- insoluble amines from water-insoluble nonbasic compounds.d  Amines Form Ammonium Salts Amines are basic - accept protons CH3NH2 + HCl CH3NH3+ Cl - I Increases solubility l bili CH3 + Cl- CH3CH2 N CH2CH3 CH3 Drug Solubility  Alkaloids Amines that are isolated from plants are known as alkaloids. They Th iinclude l d poisons, i a number b off d drugs, and d addictive substances. ▪ Nicotine - poison ▪ Codeine - drug ▪ Styrichnine - poison ▪ Heroine H i - drugd ▪ Caffeine - addictive ▪ Quinine - drug ▪ Morphine - drug ▪ Cocaine – drug ▪ Demerol - drug ▪ Methadone - drugg