Chem 102 1st Edition Lecture 20Outline of Last Lecture I. Chapter 16: Lessons 6.5-6.7 : Physical Properties of Amines, Basicity of Amines, Reactions of Amines with AcidsOutline of Current Lecture II. 6.8 – Alkylation of Ammonia and AminesIII. 6.9 – Heterocyclic AminesIV. 6.10 – Selected Biochemically Important AminesV. 6.11 – AlkaloidsVI. 6.12 – Structure and Classification of AmidesVII. 6.13 – Nomenclature for AmidesCurrent Lecture6.8 Alkylation of Ammonia and Amines• Primary amines are obtained by alkylation of ammonia in the presence of a base. - If the primary amines are not quickly removed from alkylation reaction mixture, the nitrogen atom of the amine may react with further alkyl halide molecules giving secondary and tertiary amines. • Secondary and Tertiary amines are produced in similar reactions via the alkylation of primary and secondary amines respectively.• Tertiary amines react with alkyl halides in the presence of a strong base to produce a quaternary ammonium salt. • Quaternary ammonium salts are different from amine salts – Addition of strong base does not result in “parent” amine• Quaternary ammonium salts: – Colorless, odorless, crystalline solids that have high melting points and are water-soluble. 6.9 Heterocyclic Amines• Heterocyclic amine: An organic compound with nitrogen atoms of amine groups present in a ring system. • Ring systems may be: – Saturated, unsaturated, or aromatic– >1 Nitrogen atom may be present in a given ring, and – Fused ring systems often occur. • Heterocyclic amines are important starting material for medicinal, agricultural, food and products that are important in human body – Nicotine and caffeine are two heterocyclic amines - Stimulants – Porphyrin ring, a component of hemoglobin, is a heterocyclic amine 6.10 Selected Biochemically Important AminesNeurotransmitters • A neurotransmitter is a chemical substance that is released at the end of a nerve, travels across the synaptic gap between the nerve and another nerve, and then bonds to a receptor site on the other nerve, triggering a nerve impulse • Acetylcholine: Involved in transmission of nerved impulses • Dopamine: Found in brain and its deficiency may cause Parkinson disease • Serotonin: Involved in sleep, sensory perception in mental illness. • Norepinephrine: Helps maintain muscle tone in blood vessels • Epinephrine: – An important central nervous system stimulant – Released into blood in response to pain, excitement and fear. – Increases rate and force of heart contraction and muscular strength 6.11 Alkaloids• Alkaloid: An alkaloid is a nitrogencontaining organic compounds extracted from plant material • Well known alkaloids: – Nicotine (tobacco plant) – Caffeine (coffee beans and tea leaves) – Cocaine (coca plant) – Morphine and codeine (Opium plant) • Many alkaloids are currently used in medicine. • Quinine: Isolated from cinchona tree bark -used to treat malaria. • Atropine: Isolated from the belladonna plant - used as a preoperative muscle relaxant6.12 Structure and Classification of Amides• Amides: Derivatives of carboxylic acids in which the “OH” group of the carboxylic acid is replaced by an amino (NH2) or a substituted amino (NHR or NR2). • Same rules that apply to amines to determine if they are primary, secondary or tertiary amines also apply to amides Amide Classification • Primary amides (1o) : Two hydrogen atoms are bonded to the amide nitrogen atom • Secondary amides (2o): An alkyl (or aryl) group and a hydrogen atom are bonded to the amide nitrogenatom • Tertiary amides (3o): Two alkyl (or aryl) groups and no hydrogen atoms are bonded to the amide nitrogen atom Primary, Secondary, and Tertiary Amines and Amides • The “H versus R” relationship: Lactam • Lactam: A cyclic amide. • The ring size in a lactam is indicated using a Greek letter • A lactam with a four-membered ring : Beta-lactam – Beta-carbon from the carbonyl group is bonded to the heteroatom. – The members of the penicillin family of antibiotics have fourmembered lactam ring. • A lactam with a five-membered ring : Gamma-lactam. 6.13 Nomenclature for Amides• Amides are derivatives of carboxylic acids (similar to esters)• Rules: – The ending of the name of the carboxylic acid is changed from “-ic” acid (common) or “-oic” acid (IUPAC) to -amide • Example: benzoic acid becomes benzamide– The names of groups attached to the nitrogen (2º and 3º amides) are appended to the front of the base name, using an N- prefix as a locator. • Secondary and tertiary amides involves use of the “prefix N-,” a practice we previously used in amine nomenclature • The simplest aromatic amide bears a benzene ring and an unsubstituted amide group – Name: Benzamide• Other aromatic amides are named as benzamide