Tertiary amines have no hydrogen attached to the nitrogen; this is what prevents them from forming hydrogen bonds among themselves. Just as a bit of review: Hydrogen bonding can only happen when there is a hydrogen atom attached to nitrogen, oxygen, or fluorine. One important point is that these three atoms have much higher electronegativities than the hydrogen, so they pull the electrons in the bond away from hydrogen, leaving it with a partial positive charge. The other important point is that these three atoms have unshared pairs of electrons with a partial negative charge that can attract a partially positive hydrogen atom from an adjacent molecule.
Note that the reaction is shown in two steps. In the first step, an amide and a carboxylic acid salt are formed. In the second step, the carboxylic acid salt reacts with itself (so to speak) to form another amide and a water molecule.
Amines and Amides
1Chapter 15Amines and Amides
2IntroductionAmines and amides contain one or more nitrogen atoms.Amines have an amino group.Amides are the product of reaction between an amine and acarboxylic acid derivative.
31. Amines: structure and propertiesAmines are organic derivatives of ammonia.They are basic, like ammonia.They are ammonia molecules with one or more of the hydrogensreplaced by an organic group.The amine structure is pyramidal, as is ammonia.R may be a hydrogen or an aliphatic or aromatic organic group.
51. Amines: structure and propertiesAmines are classified by the number of carbons directlybonded to the nitrogen atom:A primary amine has one: RNH2 = 1oA secondary amine has two: R2NH = 2oA tertiary amine has three: R3N = 3oVideo
61. Amines: structure and propertiesDetermine the classification of each of the followingamines.pencast
71. Amines: structure and propertiesAmines are more polar than hydrocarbons and less polarthan alcohols.Because N is less polar than O, solubility and boiling points arelower than corresponding alcoholsH-bonds are formed, but not as strongly as with –OH.
91. Amines: structure and propertiesHydrogen bonding between primary amine molecules
101. Amines: structure and propertiesOnly primary and secondary amines can formintermolecular hydrogen bonds with themselves.Boiling points for comparable molecular weight 1o, 2o,and 3o amines confirm this.Video
111. Amines: structure and propertiesPredict which compound in each pair will have the higherboiling point.pentane or 1-butanaminecyclohexane or 2-pentanamineethanamine or ethanolbutane or 1-propanaminemethanamine or waterN-methylethanamine or butanepencast
121. Amines: nomenclaturePrimary aliphatic aminesFind the longest continuous carbon chain containing the aminegroup to get the parent compound.Drop the final –e of the parent name and add the suffix -amine.Number the parent chain to give the amine carbon the lowestpossible number.Name and number all substituents as usual.Secondary and tertiary aliphatic aminesAdd the prefix N-alkyl to the name of the parent for 2o and 3oamines.
131. Amines: nomenclatureName each of the following amines.pencast
141. Amines: nomenclatureDraw structures for the following amines.3-decanamineN,N-dipropylbutanamineN-ethylcyclohexanamine2-methyl-2-pentanamineN-ethyl-2-heptanaminepencast
151. Amines: nomenclatureThe simplest aromatic amine is benzenamine, also calledaniline.Substituents on the ring are numbered.Groups attached to the nitrogen are labelled N-.4-chlorobenzenamineN,N-diethylbenzenamine
161. Amines: reactionsPreparation of aliphatic amines is by reduction of amides.Recall that reduction involves decreasing the number of bondsto oxygen and increasing the number of bonds to hydrogen.amide amine
171. Amines: reactionsIf R’ = R’’ = H, a primary amine is produced.If R’ = H and R’’ = organic group, a secondary amine isproduced.If R’ = R’’ = organic group, a tertiary amine is produced.
181. Amines: reactionsPreparation of primary aromatic amines is by reductionof nitro compounds.nitrobenzene aniline
191. Amines: reactionsAmines react as weak bases in aqueous solution.“Weak” means only partially dissociated in solution.“Base” means proton (H+) acceptor.Water acts as the proton donor (acid).amine water alkylammoniumionhydroxide ion
201. Amines: reactionsWhen an amine (a base) is neutralized by an acid, analkylammonium salt is produced.alkylammonium saltamine acid
211. Amines: reactionsNaming alkylammonium saltsStart with the name of the amine.Replace the suffix –amine with –ammonium.Add the name of the anion.3-hexanamine 3-hexanammonium chloride
221. Amines: reactionsWhat are the products of the following reactions?CH3CH2NHCH3 + H2O CH3NH2 + HBr pencast
231. Amines: reactionsAn alkylammonium salt is the conjugate acid of thecorresponding amine. Therefore, alkylammonium saltswill react with hydroxide ions to produce the amine andwater.The salt is quite soluble in water because of the charged ions.The amine is only somewhat soluble in water.Video
241. Amines: reactionsCocaineNon-water-soluble amine (“crack”)Water-soluble ammonium saltCrack cocaine, powder cocaine, and the lawCrack cocaine sentencing reform: the battle continues
251. Amines: quaternary ammonium saltsAlkylammonium salts can be prepared from 1o, 2o, or 3oamines.The nitrogen atom is bonded to three, two, or one hydrogen(s),respectively.In quaternary ammonium salts, the nitrogen is bonded tofour organic groups.
262. Heterocyclic aminesA cyclic compound with at least one nitrogen within aring structure is called a heterocyclic amine.Many heterocyclic amines are biologically important, orbiologically active.DNA, RNA, myoglobin, chlorophyllLSD, cocaine, nicotine, strychnine
293. AmidesIn amides, an amino group (–NH2) replaces the –OHgroup of carboxylic acids.ethanamideethanoic acid ethanamineLINKS:
303. AmidesAmides are (mainly) solids at room temperature and havevery high boiling points.Molecules are polar and can hydrogen bond with each other.Simple amides are soluble in water.Molecules are polar and can hydrogen bond with water.Amides do not behave like bases.
433. AmidesComparison of I.U.P.A.C. names for aspartame andneotame(3R)-3-(3,3-Dimethylbutylamino)-4-[[(1R)-2-methoxy-2-oxo-1-(phenylmethyl)ethyl]amino]-4-oxobutanoic acid(3S)-3-amino-4-[[(2S)-1-methoxy-1-oxo-3-phenylpropan-2-yl]amino]-4-oxobutanoic acid
443. AmidesAlthough the amide bond is difficult to break, hydrolysisof an amide is possible with heating in the presence ofeither a strong acid or a strong base.In strong acid: carboxylic acid + alkylammonium ionIn strong base: carboxylic acid salt + amine
453. AmidesIn strong acid: carboxylic acid + alkylammonium ion
463. AmidesIn strong base: carboxylic acid salt + amine
474. Amino acidsAn amino acid is a combination of an amino group and acarboxyl group.Proteins are polymers of amino acids (chains of amides).amino group carboxyl grouppeptide bond (amide bond)