614 AMINES m-nitrocumene as only a minor component of the nitration product. However, the conversion of 4-isopropyl-2-nitroaniline to m-isopropylnitrobenzene, which was used to illustrate reductive deamination of arylamines in the text, establishes the last step in the synthesis CH(CH3)2 CH(CH3)2 CH(CHi) NH, .Isopropyl-2- Our task simplifies itself to the preparation of 4-isopropyl-2-nitroaniline from cumene. The follow ing procedure is a straightforward extension of the reactions and principles developed in this CH(CH3), CH(CH3), CH(CH3)2 CH(CHi)2 HNO, Fe HCI CH,CCI NHCCH p-lsopropylaniline HNO 2. HO O NHCCH NHCCH Reductive deamination of 4-isopropyl-2-nitroaniline by diazotization in the presence of ethanol or hypophosphorous acid yields m-nitrocumene and completes the synthesis 22.21 Amines may be primary, secondary, or tertiary. The CaHuN primary amines, compounds of the type C4HONH2, and their systematic names are CH, CH,CH,CH,NH (CH3),CHCH,NH Butylamine Isobutylamine (2-methyl-l-propanamine) CH. CHCHCH (CH3)3CNH2 NH, sec-Butylamine 2-methyl-2- propanamine) Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
m-nitrocumene as only a minor component of the nitration product. However, the conversion of 4-isopropyl-2-nitroaniline to m-isopropylnitrobenzene, which was used to illustrate reductive deamination of arylamines in the text, establishes the last step in the synthesis. Our task simplifies itself to the preparation of 4-isopropyl-2-nitroaniline from cumene. The following procedure is a straightforward extension of the reactions and principles developed in this chapter. Reductive deamination of 4-isopropyl-2-nitroaniline by diazotization in the presence of ethanol or hypophosphorous acid yields m-nitrocumene and completes the synthesis. 22.21 Amines may be primary, secondary, or tertiary. The C4H11N primary amines, compounds of the type C4H9NH2, and their systematic names are tert-Butylamine (2-methyl-2-propanamine) (CH3)3CNH2 sec-Butylamine (2-butanamine) CH3CHCH2CH3 NH2 Butylamine (1-butanamine) CH3CH2CH2CH2NH2 Isobutylamine (2-methyl-1-propanamine) (CH3)2CHCH2NH2 HNO3 H2SO4 HO, H2O, or 1. H2O, H 2. HO CH(CH3)2 CH(CH3)2 NHCCH3 NO2 CH(CH3)2 NO2 NH2 O NHCCH3 O p-Isopropylacetanilide 4-Isopropyl-2-nitroacetanilide 4-Isopropyl-2-nitroaniline CH(CH3)2 Cumene CH(CH3)2 NO2 p-Nitrocumene CH(CH3)2 NH2 p-Isopropylaniline CH(CH3)2 NHCCH3 O p-Isopropylacetanilide HNO3 H2SO4 1. Fe, HCl 2. HO CH3CCl O CH(CH3)2 Cumene CH(CH3)2 NH2 NO2 4-Isopropyl-2- nitroaniline CH(CH3)2 NO2 m-Nitrocumene 614 AMINES Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
AMINES 615 Secondary amines have the general formula R,NH. Those of molecular formula CaHn are (CHCH,NH CH3NCH,CH,CH H H Diethylamine N-Methy propylamine (N-ethylethanamine propanamine) There is only one tertiary amine(r N)of molecular formula CahuN (N, N-dimethy methanamine) 22.22 (a) The name 2-ethyl-1-butanamine designates a four-carbon chain terminating in an amino group and bearing an ethyl group at C-2. CHaCH,CHCH,NH, CH, CH3 2-Ethyl-1-butanamine (b The prefix N-in N-ethyl-l-butanamine identifies the ethyl group as a substituent on nitrogen n a secondary amine CHI CH_ CH, CHNCH, CH N-Ethyl-l-butanamine (c) Dibenzylamine is a secondary amine. It bears two benzyl groups on nitrogen. C6H,NCH,CH5 H Dibenzylamine (d) Tribenzylamine is a tertiary amine (CBH CH2)3N Tribenzylamine (e) Tetraethylammonium hydroxide contains a quaternary ammonium ion (CH CH2)N HO (f) This compound is a secondary amine; it bears an allyl substituent on the nitrogen of cyclo- hexylamine CH,CH=CH, Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
Secondary amines have the general formula R2NH. Those of molecular formula C4H11N are There is only one tertiary amine (R3N) of molecular formula C4H11N: 22.22 (a) The name 2-ethyl-1-butanamine designates a four-carbon chain terminating in an amino group and bearing an ethyl group at C-2. (b) The prefix N- in N-ethyl-1-butanamine identifies the ethyl group as a substituent on nitrogen in a secondary amine. (c) Dibenzylamine is a secondary amine. It bears two benzyl groups on nitrogen. (d) Tribenzylamine is a tertiary amine. (e) Tetraethylammonium hydroxide contains a quaternary ammonium ion. ( f ) This compound is a secondary amine; it bears an allyl substituent on the nitrogen of cyclohexylamine. N CH2CH CH2 H N-Allylcyclohexylamine Tetraethylammonium hydroxide (CH3CH2)4N HO Tribenzylamine (C6H5CH2)3N Dibenzylamine C6H5CH2NCH2C6H5 H N-Ethyl-1-butanamine CH3CH2CH2CH2NCH2CH3 H 2-Ethyl-1-butanamine CH3CH2CHCH2NH2 CH2CH3 N,N-Dimethylethylamine (N,N-dimethylethanamine) (CH3)2NCH2CH3 Diethylamine (N-ethylethanamine) (CH3CH2)2NH N-Methylpropylamine (N-methyl-1-propanamine) CH3NCH2CH2CH3 H N-Methylisopropylamine (N-methyl-2-propanamine) CH3NCH(CH3)2 H AMINES 615 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
616 AMINES (g) Piperidine is a cyclic secondary amine that contains nitrogen in a Six-membered ring N-Allylpiperidine is a tertiary amine NCH,CH=CH, N-Allylpiperidine (h) The compound is the benzyl ester of 2-aminopropanoic acid CHaCHCOCH, CH5 The parent compound is cyclohexanone. The substituent( CH,),N-group is attached to C-4 4-(N, N-Dimethylamino)- cyclohexanone The suffix -diamine reveals the presence of two amino groups, one at either end of a three- carbon chain that bears two methyl groups at C-2. H,NCH,CCH,NH, 22.23 (a) A phenyl group and an amino group are trans to each other on a three-membered ring in this CH trans-2-Phenylcyclopropylamine (b) This compound is a tertiary amine. It bears a benzyl group, a methyl group, and a 2-propynyl CsH CH2-N CH2C≡CH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(g) Piperidine is a cyclic secondary amine that contains nitrogen in a six-membered ring. N-Allylpiperidine is a tertiary amine. (h) The compound is the benzyl ester of 2-aminopropanoic acid. (i) The parent compound is cyclohexanone. The substituent (CH3)2N— group is attached to C-4. ( j) The suffix -diamine reveals the presence of two amino groups, one at either end of a threecarbon chain that bears two methyl groups at C-2. 22.23 (a) A phenyl group and an amino group are trans to each other on a three-membered ring in this compound. (b) This compound is a tertiary amine. It bears a benzyl group, a methyl group, and a 2-propynyl group on nitrogen. N-Benzyl-N-methyl-2-propynylamine (pargyline) C6H5CH2 CH2C CH CH3 N trans-2-Phenylcyclopropylamine (tranylcypromine) C6H5 H H NH2 H2NCH2CCH2NH2 CH3 CH3 2,2-Dimethyl-1,3- propanediamine 4-(N,N-Dimethylamino)- cyclohexanone (CH3)2N O H CH3CHCOCH2C6H5 NH2 O Benzyl 2-aminopropanoate CH2 N-Allylpiperidine NCH2CH 616 AMINES Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
AMINES 617 (c) The amino group is at C-2 of a three-carbon chain that bears a phenyl substituent at its CH-CHCHCH 1-Phenyl-2-propanamine (d) Phenylephrine is named systematically as an ethanol derivative CHCHN 1-(m-Hydroxyphenyl)- 22. 24(a) There are five isomers of C,Hon that contain a benzene ring C6Hs CH,NH, C6HSNHCH CB3、2 CH3 NH Methylaniline -methylaniline Methylaniline (b) Benzylamine is the strongest base because its amine group is bonded to an sp-hybridized carbon. Benzylamine is a typical alkylamine, with a k, of 2 x 10. All the other isomers are arylamines, with K, values in the 10range (c) The formation of N-nitrosoamines on reaction with sodium nitrite and hydrochloric acid is a characteristic reaction of secondary amines. The only CHON isomer in this problem that is a HCL. H,O CBHSNHCH, NaNO CBHSNCH N-Methyl-N (d) Ring nitrosation is a characteristic reaction of tertiary arylamines R, Tertiary arylamine p-Nitroso-N, N-dialkylaniline None of the CHoN isomers in this problem is a tertiary amine; hence none will undergo ring Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
(c) The amino group is at C-2 of a three-carbon chain that bears a phenyl substituent at its terminus. (d) Phenylephrine is named systematically as an ethanol derivative. 22.24 (a) There are five isomers of C7H9N that contain a benzene ring. (b) Benzylamine is the strongest base because its amine group is bonded to an sp3 -hybridized carbon. Benzylamine is a typical alkylamine, with a Kb of 2 105 . All the other isomers are arylamines, with Kb values in the 1010 range. (c) The formation of N-nitrosoamines on reaction with sodium nitrite and hydrochloric acid is a characteristic reaction of secondary amines. The only C7H9N isomer in this problem that is a secondary amine is N-methylaniline. (d) Ring nitrosation is a characteristic reaction of tertiary arylamines. None of the C7H9N isomers in this problem is a tertiary amine; hence none will undergo ring nitrosation. HCl, H2O NaNO2 Tertiary arylamine NR2 p-Nitroso-N,N-dialkylaniline ON NR2 N-Methylaniline C6H5NHCH3 N-Methyl-Nnitrosoaniline C6H5NCH3 N O HCl, H2O NaNO2 o-Methylaniline CH3 NH2 m-Methylaniline CH3 NH2 p-Methylaniline CH3 NH2 Benzylamine C6H5CH2NH2 N-Methylaniline C6H5NHCH3 1-(m-Hydroxyphenyl)- 2-(methylamino)ethanol CHCH2N HO OH H CH3 C6H5CH2CHCH3 NH2 1-Phenyl-2-propanamine (amphetamine) AMINES 617 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website
618 AMINES 22.25(a) Basicity decreases in proceeding across a row in the periodic table. The increased nucle charge as one progresses from carbon to nitrogen to oxygen to fluorine causes the electrons to be bound more strongly to the atom and thus less readily shared H, C: HN: >H 10-16 3.5×10-4 conJugate (b) The strongest base in this group is amide ion, H,N, and the weakest base is water, H,O Ammonia is a weaker base than hydroxide ion; the equilibrium lies to the left. H, H,o NH4+ Weaker Weaker acid The correct order is H,N O (c) These anions can be ranked according to their basicity by considering the respective acidities of thej Base Conjugate acid Ka of conjugate acid H,N H-N HO HC≡N 7.2×10-10 2.5×101 The order of basicities is the opposite of the order of acidities of their conjugate acids (d) A carbonyl group attached to nitrogen stabilizes its negative charge. The strongest base is the nion that has no carbonyl groups on nitrogen; the weakest base is phthalimide anion, which has two carbonyl groups Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website
22.25 (a) Basicity decreases in proceeding across a row in the periodic table. The increased nuclear charge as one progresses from carbon to nitrogen to oxygen to fluorine causes the electrons to be bound more strongly to the atom and thus less readily shared. (b) The strongest base in this group is amide ion, H2N– , and the weakest base is water, H2O. Ammonia is a weaker base than hydroxide ion; the equilibrium lies to the left. The correct order is (c) These anions can be ranked according to their basicity by considering the respective acidities of their conjugate acids. Base Conjugate acid Ka of conjugate acid H2N H3N 1036 HO H2O 1016 7.2 1010 2.5 101 The order of basicities is the opposite of the order of acidities of their conjugate acids. (d) A carbonyl group attached to nitrogen stabilizes its negative charge. The strongest base is the anion that has no carbonyl groups on nitrogen; the weakest base is phthalimide anion, which has two carbonyl groups. Strongest base N N O Weakest base N O O NO3 Weakest base Strongest base H2N HO C N HON O O O N O O C N HC N NH3 Strongest base H2N HO H2O Weakest base Weaker acid H2O Weaker base NH3 Stronger base OH Stronger acid NH4 1060 Strongest base H3C 1036 H2N 1016 HO 3.5 104 Weakest base F of conjugate acid Ka 618 AMINES Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website