AminesAmines are carbon – hydrogen – nitrogencompounds.Amines occurs widely in living organisms.Many amines are naturally occurringcompounds that are very activephysiologically.Numerous drugs used for the treatment ofmental illness, hay fever, heart problems,and other physical disorders are amines.
Bonding Characteristics of Nitrogen Atoms in Organic Compounds An understanding of the bondingcharacteristics of the Nitrogen atom is aprerequisite to our study of amines.Nitrogen is a member of Group VA of theperiodic table; it has five valence electronsand it will form three covalent bonds tocomplete its octet of electrons.
In Organic Chemistry,carbon forms four bonds. 4 valence electron 4 covalent bond No nonbonding electron pairnitrogen forms three bonds 5 valence electron 3 covalent bond 1 nonbonding electron pairOxygen forms two bonds 6 valence electron 2 covalent bond 2 nonbonding electron pair
Structure and Classification of AminesAn Amine is an organic derivative ofammonia (NH4) in which one or morealkyl, cycloalkyl, or aryl groups areattached to the nitrogen atom.Amines are classified as primary (10),secondary (20), or tertiary (30) on thebasis of how many hydrocarbon groups arebonded to the ammonia nitrogen atom.
Primary Amine Is an amine in which the nitrogen atom is bonded to one hydrocarbon group and two hydrogen atoms. The generalized formula for a primary amine is RNH2.The functional grouppresent in a primary amine,the NH2 group is called anAmino group.An Amino group is the -NH2 functional group. CH3 – NH2
Secondary Amine Is an amine in which the nitrogen atom is bonded to two hydrocarbon groups and one hydrogen atom. The generalized formula for a secondary amine is R2NH. CH3 – NH – CH3
Tertiary Amine Is an amine in which the nitrogen atom is bonded to three hydrocarbon groups and no hydrogen atom. The generalized formula for a tertiary amine is R3N.
Classify Amines each of the following Amines as a Primary, Secondary, or Tertiary This is a secondary1) CH3 – NH amine because the nitrogen is bonded to both a methyl group and phenyl group2) CH3 – N – CH3 Here we have a tertiary amine because the CH3 nitrogen atom is bonded to three methyl groups.
This is also a tertiary3) N amine; the nitrogen atom is bonded to two CH3 phenyl groups and a methyl group.4) CH3 This is a primary amine. The nitrogen atom is bonded to only NH2 one carbon atom.
Physical Properties of AminesThe methylamines (mono-, di-, tri-) and ethylamine aregases at room temperature and have ammonia-likeodors.Most other amines are liquid, and many have odorresembling that of raw fish.A few amines, particularly diamines, have strong,disagreeable odors.The foul odor arising from dead fish and decaying fleshis due to amines released by the bacterialdecomposition of protein.
Diamines putrescine and cadaverine are two“odoriferous” compounds. H2 N – (CH2 )4 – NH2 H2 N – (CH2 )5 – NH2 Putrescine Cadaverine 1,4-butanediamine 1,5-pentanediamineThe simples amines are irritating to the skin, eyes, andmucous membranes and are toxic by ingestion.Aromatic amines are generally toxic.Many amines are readily absorbed through the skin andaffect both the blood and the nervous system.
The boiling points of amines are intermediatebetween those of alkanes and alcohols of similarmolecular mass.Amines are higher than alkane boiling point,because hydrogen bonding is possible betweenamine molecules but not between alkane molecules. Intermolecular hydrogen bonding of amines involves the hydrogen atoms and nitrogen atoms of the amino group.
Tertiary amines have lower boiling pointthan primary and secondary aminesbecause intermolecular hydrogenbonding is not possible in tertiaryamines.Secondary and tertiary amines have nohydrogen atoms directly bonded to thenitrogen atom.
The boiling point of amines are lower than those ofcorresponding alcohols, because N – H bonds areweaker than O – H bonds. Note: The difference in hydrogen-bond strength results from electronegativity differences, nitrogen is less electronegative than oxygen.Element Electronegativity Difference valuesNitrogen 3.0Hydrogen 2.1 0.9 Oxygen 3.5Hydrogen 2.1 1.4
Amines with fewer than six carbon atoms areinfinitely soluble in water.This solubility results from hydrogen bondingbetween the amines and water. Even tertiary amines are water- soluble, because amine nitrogen atom has a nonbonding electron pair that can form a hydrogen bond with a hydrogen atom of water.
Basicity of AminesAmines, like ammonia, are weak bases.Ammonia’s weak-base behavior results from itsaccepting a proton (H+) from water to produceammonium ion (NH4+) and hydroxyl ion (OH- ) NH3 + HOH = NH4 + + OH- ammonia Ammonium ion Hydroxide ionAmines behave in a similar manner. +CH3 – NH2 + H OH = CH3 + NH3 + OH-Methylamine Methylammonium ion Hydroxide ion
Amines, like ammonia, have a pair of unsharedelectrons on the nitrogen atom present. These unshared electrons can accept a hydrogen ion from water.ammonia amine Thus, both amines and ammonia produce basic aqueous solution
The result of the interaction of an aminewith water is a basic solution containingsubstituted ammonium ions andhydroxide ions.A substituted ammonium ion is anammonium ion in which one or more alkyl,cycloalkyl, or aryl groups have beensubstituted for hydrogen atom.Substituted ammonium ions alwayscontain one or more hydrogen atom thantheir “parent” amine. They also alwayscarry a +1 charge, whereas the “parent”amine is a neutral molecule.
Naming the positive ion that results from the interaction of an amine with water is based on the following two rules: Rule 1: For alkylamine, the ending of the name of the amine is changed from amine to ammonium ion H2 O + - CH3 – CH2 – NH2 CH3 – CH2 – NH3 + OH Ethylamine Ethylammonium H2 O + ion -CH3 – N – CH2 – CH3 CH3 – NH – CH2 –CH3 + OH CH3 CH3Ethyldimethylamide Ethyldimethylammonium ion
Rule 2: For aromatic amines, the final –e ofthe name of the amine is replaced by –iumion. + NH2 CH3-NH2 + NH3 N – methylaniliniumAniline ion Anilinium ion
Name the following substituted ammonium or substituted anilinium ions. + 1) CH3 – CH2 – NH2 – CH2 – CH3 1) diethylammonium ion 2) trimethylammonium ion + + 2) CH3 – NH – CH3 4) CH3 – NH – CH3 CH33) isobutylammonium ion +3) CH3 – CH – CH2 – NH3 4) N,N dimethylanilinium ion CH3
Amine SaltThe reaction of an acid with a base(neutralization) produces a salt.CH3 .. – NH + H – Cl + CH3 – NH2Cl - 2 amine acid Amine saltAromatic amines react with acids in a similarmanner. CH3 .. + H – Cl – NH + CH3 – NH2Cl - acid amine Amine salt
An amine salt is an organic compound inwhich the positive ion is a mono-, di-, ortrisubstituted ammonium ion (RNH3 + ,R2NH2+ , or R3NH+ ) and the negative ioncomes from an acid.Amine salt can be obtained in crystallineform (odorless, white crystals) byevaporating the water from the acidicsolutions in which amine salt are prepared.
Amine salt are named using standardnomenclature procedures for ioniccompound.The name of the positive ion, thesubstituted ammonium or anilinium ion, isgiven first and followed by a separate wordfor the name of the negative ion.2 1 +CH3 – CH2 – NH3 Cl - Ethyl ammonium chloride + - dimethyl ammonium bromideCH3 – NH2 – CH3 Br
An older system for amine slats, still usedin the pharmaceutical industry, treat aminesalts as amine- acid complexes rather thanas ionic compound. CH3 – NH3 HCl Dimethylamine hydrochloride CH3 + - CH3 – NH3ClRather than as CH3 dimethyl ammonium chloride
Many people unknowingly use acids to form amineslats when they put vinegar or lemon juice on fish.Such action converts amines in fish ( often smellycompounds) to salts, which are odorless.The process of forming amine salts with acids is aneasily reversed process.Treating amine salts with a strong base such asNaOH regenerates the “parent” amine.CH3 – NH3 Cl + NaOH CH3 – NH2 + NaCl + H2 O Amine salt base Amine salt
The “opposite nature” of the processes of amine saltformation from an amine and the regeneration of theamine from its amine salt can be diagrammed asfollows: Acid Protonation An Amine An Amine Salt Deprotonation BaseAn amine gains hydrogen ion to produce an aminesalt when treated with an acid (protonation.An amine salt loses a hydrogen ion to produce anamine when treated with a base (deprotonationreaction)
Write the structures of the products that forms when each of the following reactions involving amines or amine salts takes place.1) CH3 – NH – CH3 + HCl + - ¨ CH3 – NH – CH3 + HCl CH3 – NH2 – CH3Cl + -2) CH3 – NH2 – CH3Cl + - CH3 – NH2 – CH3Cl + NaOH ¨ CH3 – NH – CH3 + NaCl + H2O
Heterocyclic AminesHeterocyclic amine is an organic compoundin which nitrogen atoms of amine group arepart of either an aromatic or a nonaromaticring system.Heterocyclic amine are the most commontype of heterocyclic organic compoundHeterocyclic amines are the firstheterocyclic compounds we haveencountered that have nitrogenheteroatoms.
Selected Structural Formulas of Heterocyclic amines that serve as “parent” molecule for complex amine derivatives. Pyridine Pyrrole Quinoline PyrimidinePyrrolidine Imidazole Indole Purine
Heterocyclic amines often have strong odor,some agreeable and others disagreeable.The pleasant aroma of many heat-treatedfood is caused by heterocyclic aminesformed during the treatment.The compounds responsible for thepervasive odors of poop popcorn and hotpeanut are heterocyclic amines. O CH3 C CH3 O CH3Methyl- 2- pyridyl ketone 2-Methoxy-5-methylpyrazine odor of popcorn odor of peanut
Isomerism for AminesConstitutional isomerism in amines canarise from several causes.1. Different carbon atom arrangements produce isomers, as in CH3 – CH2 – CH2 – CH2 – CH2 NH2 1-Pentanamine C5 H11 – NH2 CH3 – CH2 – CH – CH2 – NH2 CH3 2 Methyl-1-butanamine C5 H11 – NH2
2) Different positioning of the nitrogen atom on a carbon chains is another cause for isomerism. CH2 – CH2 – CH2 – CH3 NH2 1-Butanamine CH3 – CH – CH2 – CH3 NH2 2-Butanamine
Nomenclature for AminesA. Naming Primary Amines 1 methane1 2 3 4 2 ethaneCH3 – CH – CH2 – CH3 3 propane 4 butane NH2 2- butan amine 5 pentane1. Select as the parent 3. Number the parent chaincarbon chain the longest from the end nearest thechain to which the nitrogen nitrogen atom.atom is attached. 4. The position of2. Name the parent chain by attachment of the nitrogenchanging the –e ending of atom is indicated by athe corresponding alkane number in front of thename to –amine. parent chain name.
In diamines, the final –e of the carbonchain name is retained for easepronunciation. 2 4 3 2 1 1 H2N – CH2 – CH2 – CH2 –CH2 – NH2 1 ,4- butane di amine 1 methane 2 ethane 3 propane 4 butane 5 pentane
Secondary and Tertiary Amines are namedas N- substituted primary amines.The largest carbon group bonded to thenitrogen is used as the parent aminename.The names of the other group attached tothe nitrogen are appended to the front ofthe base name, and N- or N,N- prefixes areused to indicate that those groups areattached to the nitrogen atom rather thanto the base carbon chain.
Simplest aromatic amine, a benzene ringbearing an amino group, is calledaniline.Other simple aromatic amines are namedas derivatives of aniline. NH2 NH2 NH2 Cl 1 2 Di 3 Cl Cl Aniline m - Chloro aniline 2 – 3, di chloroaniline
In secondary and tertiary aromatic amines,the additional group or groups attached tothe nitrogen atom are located using a capitalN- NH – CH2 – CH3 NH – CH3 CH3 N- Ethylaniline 3,N Dimethylaniline H3C – N – CH3 N- N Dimethylaniline
Assign IUPAC name to each of the following amines.1) CH3 – CH2 – NH – (CH2 )4 – CH3 N-ethyl-1-pentanamine2) Br NH2 4-bromoaniline3) H2N – CH2 – CH2 – NH2 1,2-Ethanediamine4) N N,N - Dimethylethanamine