Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Power Point to Accompany Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping, and Caret 4th ed Chapter 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16-1 16.1 Amines Amines have these structures: RNH2, R2NH, R3N (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. RNH2, R2NH, R3N 1o 2o 3o 16-2 Amines: Physical properties Most amines up to 5 or 6 carbons H are water soluble CH N due to hydrogen 3 bonding with the H water molecule. O H H O H H 16-3 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 1o or 2o of similar molecular weight. C4H8 (58), bp 0 oC C3H7NH2 (59), bp 48 oC o C3H7OH (60), bp 97 C 16-4 Amine names: Chem Abstracts Primary aliphatic amines are named by dropping the final –e of the parent name and adding the suffix -amine. Name: CH3CH2NH2 ethanamine 16-5 Amine names: Chem Abstracts-2 The prefix N-alkyl is added to the name of the parent for 2o and 3o amines. Name: H CH3CH2N CH2CH3 N-ethylethanamine 16-6 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. CH3CH CH3 2-aminopropane NH2 CH3CH CH3 N-methyl-2-aminopropane NH CH3 16-7 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: CH3CH2CH CH3 CH3 NH Methylsec-butylamine 16-8 Amine names Aromatic amines are named as N-substituted derivatives of aniline. (See aromatics) Name a) and b): a) m-nitroaniline NH2 b) N-methylaniline a) HN CH3 NO2 b) 16-9 Reactions of Amines: Preparation Aliphatic amines are prepared via reduction of amides. E. g. O [H] CH3CH2C NH CH3 CH3CH2CH2 NH CH3 Aromatic amines are prepared via reduction of nitro compounds. E. g. NO2 [H] NH2 16-10 Reactions of Amines: Basicity Amines are weak bases. They accept protons from water making solutions basic. CH3CH2 NH2 + H2O + CH3CH2 NH3 + OH 16-11 Reactions of Amines: Neutralization Amines form salts by accepting a proton from strong mineral acids. Converting amines to salts often makes insoluble amines soluble!!!!! CH3CH2CH2NH2 + HCl + CH3CH2CH2NH3 Cl Name amine salts by replacing the suffix –amine with ammonium and the name of the anion. E. g. propylammonium chloride 16-12 Reactions of Amine Salts: Neutralization Amine salts revert to the amine (donate a proton) in strong base. + H3N Cl H2N + NaOH NO2 + NaCl + H2O NO2 16-13 Amine Reactions: “Quats” 3o amines react with alkyl chlorides to give quaternary ammonium salts which are very important in biochemistry. CH3 CH3 N + CH3Cl CH3 CH3 + CH3 N CH3 Cl CH3 16-14 “Quats” cont. CH3 Cl+ C18H37 N CH2 CH3 CH3 Cl+ CH3N CH2CH2OH CH3 Benzalkonium chloride (ZephiranTM) and choline are important examples. 16-15 16.2 Heterocyclic Amines Heterocyclic amines have at least one nitrogen in the ring. MANY are physiologically active and many are critical in biochemistry. HN N pyrrole N N N pyrimidine N N N H purine 16-16 Examples of Heterocyclic Amines CH3 N N nicotine H2N CH2CH2 N histamine N H CH2 CH2 NH2 HO N H serotonin, a neurotransmitter 16-17 Examples of Heterocyclic Amines-2 H3C O HO CH2 NH2 CH2 OH O H C N NCH3 3 pyridoxamine HO a B vitamin Codine HO HO CH2 CH2 NH2 dopamine neurotransmitter 16-18 16.3 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. O CH3C NH2 O + CH3C NH2 16-19 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. O CH3C NH2 ethanamide or acetamide O CH3CH2C NH CH3 N-methylpropanamide 16-20 Preparation of Amides 1o and 2o amines react with acid chlorides to give amides. O CH3C Cl + NH2 O H CH3C N + HCl The acid chloride transfers its acyl group to the N of the amine. 16-21 Preparation of Amides-2 1o and 2o amines react with acid anhydrides to give amides. E. g. with acetic anhydride. O O CH3COC CH3+ H2NCH3 OH O CH3C NCH3+CH3COH 16-22 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. H O + H3N C C O aC R1 16-23 Peptides A peptide is a polymer of about 2-100 amino acids linked by the peptide(amide) bond. As the amino group and the carboxyl group link, water is lost. H O H O H O + + + H3N C C O H3N C C O H3N C C O R1 -H2O R1 -H2O R1 H O H O H O + H3N C C N C C N C C O H H R1 R1 R1 Peptide bonds 16-24 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. C CH3CH2C NH CH3+ H3O+ C CH3CH2C OH + + NH3 CH3 C CH3CH2C NH CH3+ NaOH C CH3CH2C ONa + H2N CH3 16-25 16.4 Amino Acids and Protein Synthesis a-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. HC H2N C C transfer RNA R Aminoacyl group from amino acid 16-26 16.5 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. HO HO CH2CH2 NH2 16-27 Neurotransmitters-cont. Catecholamines-cont. Epinephrine (adrenaline) and norepinephrine are involved in the fight or flight response. CH3 OH CH CH2 NH HO HO epinephrine (nor=no CH3) HO + CH2CH2NH3 serotonin N Serotonin H A deficiency is associated with depression, bulemia and anorexia nervosa. It also affects pain perception, thermoregulation, and sleep. 16-28 Neurotransmitters-cont. Histamine is released + during an allergic response. CH2CH2NH3 Benadryl is a typical + antihistamine used for HN NH colds and other allergic histamine responses. Acetylcholine functions at the O + neuromuscular CH3C O CH2CH2N CH3 junction to cause acetyl choline muscles to contract. 3 16-29 The End Amines and Amides 16-30