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Lecture 7: Amines and Amides Amines Amines Are derivatives of ammonia NH3. Contain N attached to one or more alkyl or aromatic groups. 18.1 Amines CH3—NH2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings CH3 ⏐ CH3—NH CH3 ⏐ CH3—N—CH3 NH2 1 2 Classification of Amines Models of Amines Amines are classified as primary, secondary, or tertiary. In a primary (1°) amine, one carbon group is bonded to the nitrogen atom. A secondary (2°) amine has two carbon groups. A tertiary (3°) amine has three carbon groups. H CH3 CH3 | | | CH3—N—H CH3—N—H CH3—N—CH3 1° 2° 3° The three-dimensional models show the shapes of amine molecules with one or more alkyl groups bonded to the nitrogen atom. 3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 4 1 Naming Simple Amines IUPAC Names of Amines Simple amines Are named as alkylamines. List the names of the alkyl groups bonded to the N atom in alphabetical order in front of amine. In the IUPAC system, Amines are named as alkanamines. The -e in the alkane name of the longest chain is changed to -amine. The chain is numbered to locate the amine group and substituents. NH2 | CH3—CH—CH3 CH3—CH2—NH2 Ethanamine 2-Propanamine CH3—CH2—NH2 ethylamine CH3—NH—CH3 dimethylamine CH3 | CH3—N—CH2—CH3 ethyldimethylamine 5 Naming Secondary and Tertiary Amines Learning Check In a secondary or tertiary amine, The longest alkane chain is numbered. Each alkyl group bonded to the N atom is named as a N-alkyl group HN—CH3 | CH3—CH2—CH2—NH—CH3 CH3—CH—CH2—CH3 3 2 1 N-Methyl-1-propanamine 1 2 3 6 Give the common and IUPAC names, and classify as primary, secondary, or tertiary: A. CH3—CH2—CH2—NH2 CH3 | B. CH3—CH2—N—CH3 4 N-Methyl-2-butanamine 7 8 2 Learning Check Aromatic Amines Write a structural formula for A. 2-pentanamine B. The amine of benzene is aniline. Alkyl groups on the N use the prefix N- and the alkyl name. NH2 N-methyl-1-butanamine NH2 NH CH3 Cl Aniline 3-chloroaniline N-methylaniline 9 10 Learning Check Solution Give a name for each: A. CH3—NH—CH2—CH3 A. B. C. CH3 | CH3—CH2—N—CH2—CH2—CH2—CH3 CH3—NH—CH2—CH3 ethylmethylamine; N-methylethanamine CH3 | B. CH3—CH2—N—CH2—CH2—CH2—CH3 N-ethyl-N-methyl-1-butanamine NH2 C. 11 NH2 aniline 12 3 Boiling Points of Amines, Alcohols, and Alkanes Lecture 7: Amines and Amides The boiling points of amines are Higher than alkanes. Lower than alcohols of similar mass. 18.2 Properties of Amines Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 13 14 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Hydrogen Bonding for Amines Solubility in Water The polar N-H bond Provides hydrogen bonding in 1°and 2° amines, but not 3°. In amines is not as polar as the O-H bonds in alcohols. Amines are soluble in water If they have 1-5 carbon atoms. Because the N atom in smaller amines forms hydrogen bonds with the polar O-H bond in water. 15 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 16 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 4 Learning Check Solution Consider the following compounds: 1. CH3—CH2—CH2—NH2 2. CH3—CH2—NH—CH3 3. CH3—CH2—CH2—CH3 Consider the following compounds: 1. CH3—CH2—CH2—NH2 2. CH3—CH2—NH—CH3 3. CH3—CH2—CH2—CH3 A. Which compound has the highest boiling point? 1. CH3—CH2—CH2—NH2 A. Which compound has the highest boiling point? B. Which compound(s) is(are) soluble in water? 1. CH3—CH2—CH2—NH2 2. CH3—CH2—NH—CH3 B. Which compound(s) is(are) soluble in water? 17 Amines React as Bases Neutralization forms Amine Salts NH4+ + OH– An amine salt Forms when an amine is neutralized by acid. Is named by replacing the amine part of the name with ammonium followed by the name of the negative ion. ammonium hydroxide CH3—NH2 + HCl CH3—NH3+Cl– methylamine methylammonium chloride Amines are Bronsted-Lowry bases that attract a H+ from H2O to the N atom. Weak bases in water. NH3 + H2O CH3—NH2 + H2O 18 CH3—NH3+ + OH– Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings methylammonium hydroxide 19 20 5 Properties of Amine Salts Cocaine Amine salts are Solids at room temperature. Soluble in water and body fluids. The form used for drugs. Cocaine Is sold illegally as an amine salt. Is reacted with NaOH to produce the free amine form known as “crack”. 21 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 22 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Learning Check Solution Write the equation for ethylamine when it reacts with each of the following: Write the equation for ethylamine when it reacts with each of the following: 1. + H2O 1. CH3—CH2—NH2 + H2O CH3—CH2—NH3+ OH– 2. + HCl 2. CH3—CH2—NH2 + HCl CH3—CH2—NH3+ Cl– 23 24 6 Lecture 7: Amines and Amides Heterocyclic Amines 18.3 Heterocyclic Amines and Alkaloids A heterocyclic amine Is a cyclic organic compound. Has a five- or six-atom ring. Contains one or more nitrogen atoms. 25 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Examples of Heterocyclic Amines Learning Check Identify the following heterocyclic amines: N N H Pyrrolidine N H Pyrrole H Piperidine N 1. 2. 3. N H Imidazole N N N N 26 N N N N N H H H N H Pyridine Pyrimidine Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Purine 27 28 7 Solution Alkaloids Identify the following heterocyclic amines: 1. 2. N N N H H H 1. piperidine Alkaloids are Physiologically active nitrogen-containing compounds. Produced by plants. Used as stimulants, anesthetics, and antidepressants. Often habit forming. 3. 2. pyrrole 3. imidazole 29 Caffeine 30 Nicotine Caffeine Is a stimulant of the central nervous system. Is found in coffee beans, tea, chocolate, and soft drinks. Contains an imidazole ring. Nicotine Increases the adrenaline level in the blood. Causes addiction to tobacco. Contains a pyrrolidine ring. N CH3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 31 32 8 Alkaloids Related to Morphine Morphine and Codeine Alkaloids Such as morphine and codeine are produced by the poppy. Have been used for centuries as painkillers. Such as heroin and codeine are modifications of morphine. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 33 Pharmacology 34 Pharmacology An area of research in pharmacology Is to design drugs such as procaine, lidocaine, and demerol that retain some of the characteristics of alkaloids. Is to modify the structures of cocaine and morphine to produce anesthesia, but without the addictive side effects. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 35 36 9 Learning Check Solution Identify the heterocyclic amine in serotonin. Identify the heterocyclic amine in serotonin. CH2 CH2 CH2 NH2 HO HO serotonin CH2 NH2 pyrrole N N H H 37 Lecture 7: Amines and Amides 38 Preparation of Amides Amides are prepared By reacting a carboxylic acid with ammonia or 18.4 Amides an amine (1° or 2°). Using heat. O || Heat CH3—C—OH + NH3 O || CH3—C—NH2 + H2O O O || Heat || CH3—C—OH + CH3—NH2 CH3—C—NH—CH3 + H2O Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 39 40 10 Amides Naming Amides In amides, an amino group(–NH2) replaces the –OH group of carboxylic acids. O O || || CH3—C—OH CH3—C—NH2 Amides are named as alkanamides. IUPAC replaces –oic acid ending with –amide. Common names replace -ic acid ending with –amide. O || Methanamide (IUPAC) H—C—NH2 Formamide (common) O || CH3—CH2—C—NH2 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Propanamide (IUPAC) Propionamide (common) 41 Naming Amides with N Groups 42 Aromatic Amides An alkyl group bonded to the N atom is named as N-alkyl in front of the amide name. O H || │ N-methylethanamide (IUPAC) CH3 —C—N—CH3 N-methylacetamide (common) O H || │ CH3—CH2 —C—N—CH2—CH3 N-ethylpropanamide (IUPAC) N-ethylpropionamide (common) 43 The amide of benzene is named benzamide. O O C NH2 C NH CH3 Benzamide N-methylbenzamide 44 11 Learning Check Solution Give the IUPAC and common names for the following: A. O || CH3–CH2–CH2–C–NH2 B. O H || │ CH3–C–N–CH2–CH3 A. B. O || CH3–CH2–CH2–C–NH2 butanamide; butryamide OH || │ CH3–C–N–CH2–CH3 N-ethylethanamide; N-ethylacetamide 45 46 Learning Check Solution Draw the structures of A. A. pentanamide B. N-methylbutyramide pentanamide O || CH3–CH2–CH2–CH2–C–NH2 B. 47 N-methylbutyramide O || CH3–CH2–CH2–C–NH–CH3 48 12 Classification of Amides Learning Check Amides are classified according to the number of carbon atoms bonded to the nitrogen atom. O H || | CH3—C—N—H Primary (1°) amide O H || | CH3—C—N—CH3 O CH3 || | CH3 —C—N—CH3 Give the common and IUPAC names for the following amides and classify as primary, secondary, or tertiary: A. O || CH3—CH2—CH2—C—NH2 B. O CH3 || | CH3—C—N—CH2—CH3 Secondary (2°) amide Tertiary (3°) amide 49 Some Amides in Health and Medicine Solution Urea is the end product of protein metabolism. O || A. CH3—CH2—CH2—C—NH2 butryamide (common); butanamide (IUPAC) primary(1°) amide B. 50 Saccharin is an artificial sweetener. Some amides such as phenobarbital, Nembutal and Seconal are barbiturates. Acetaminophen is used to reduce fever and pain. O CH3 || | CH3—C—N—CH2—CH3 N-ethyl-N-methylacetamide (common); N-ethyl-N-methylethanamide (IUPAC) tertiary (3°) amide 51 52 13 Physical Properties of Amides Some Amides in Health and Medicine Amides That are primary (−NH2) or secondary (−NH−) form hydrogen bonds. That are primary have higher melting points than secondary. That are tertiary (no H on N) do not form hydrogen bonds and have lower melting points. All form hydrogen bonds with water. With 1-5 carbon atoms are soluble in water. 53 54 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Hydrogen Bonding of Amides O || CH3—C—N—H | H O || CH3—C—N—H | H Lecture 7: Amines and Amides 18.5 Hydrolysis of Amides Hydrogen bonding occurs between primary amides. 55 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 56 14 Hydrolysis of Amides Hydrolysis Reactions acid hydrolysis Amides undergo acid hydrolysis base hydrolysis carboxylic acid ammonium salt salt of carboxylic acid and an amine or ammonia O || CH3—C—NH2 HCl + H2O NaOH O || CH3—C—OH + NH4+Cl– O || CH3—C—O– Na+ + NH3 base hydrolysis 57 Learning Check 58 Solution Write the equation for the hydrolysis of N-ethylpropanamide with NaOH. Write the products of the hydrolysis of N-ethylpropanamide with NaOH. O || CH3—CH2—C—N—CH2—CH3 + NaOH N-ethylpropanamide O || CH3—CH2—C—O– Na+ + CH3—CH2—NH2 59 60 15