Chapter 19. Amines (胺) 19.1 Nomenclature In common nomenclature most prima ry amines are named as alkylamine s. In systematic nomenclature the y are named by adding the suffix –amine to the name of the chain o r ring system to which the NH 2 gro up is attached with elision of th e final e Prim ary A m ines; ²®°· CH 3 NH 2 CH 3 CH 2 NH 2 CH 3 CH 2 CH 2 NH 2 M ethylamine (m ethanam ine) Ethylamine (ethanam ine) Propylam ine (Propanam ine) C om m on nam e; IU PA C nam e; ¼×°· ÒÒ°· ±û°·
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Chapter 19. Amines ( 胺) 19.1 Nomenclature In common nomenclature most primary amines are named as alkylamines. In systematic nomenclature they are named.
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Chapter 19. Amines ( 胺)19.1 Nomenclature
In common nomenclature most primary amines are named as alkylamines. In systematic nomenclature they are named by adding the suffix –amine to the name of the chain or ring system to which the NH2 group is attached with elision
19.2B Structure of aminesThe Nitrogen atom of most amines is like that of ammonia; it is approximately sp3 hybridized. The three alkyl groups (or hydrogen atoms) occupy corners of a tetrahedron; the sp3 orbital containing the unshared electron pair is directed toward the other corner. We describe the geometry of the amine by the location of the atoms as
If the alkyl groups of a tertiary amine are all different the amine will be chiral. There will be two enantiomeric forms of the tertiary amine. In practice, however, resolution is usually impossible b
ecause the enantiomers interconvert rapidly.
N
R'
R''
R'''
NR''
R'
R'''
Intercomversion of amine enantiomersÊå°·¶ÔÓ³ÌåÏ໥ת»»£¬ÄÑÒÔ²ð·Ö¡£
6 kcal mol-1
Ammonium salts cannot undergo inversion because they do not have an unshared pair. Therefore, those quaternary ammonium salts ( 季胺盐) with four different groups are chiral and can be resolved into separate (rel
atively stable) enantiomers.
N
R'
R''
R'''
NR''
R'
R'''
Quaternary ammonium salts such as these can be resolved
¼¾°·ÑζÔÓ³Ìå²»ÄÜÏ໥ת»»£¬¿ÉÒÔ²ð·Ö³Éµ¥¸ö¶ÔÓ³Ìå¡£
R'''' R''''+
X-
+
X-
19.3 Basicity of amines( 胺的碱性) : Amine salts (胺
盐)Amines are relatively weak bases. They are stronger bases than water but are far weaker bases than hydroxide ions (OH-), alkoxide ions
The tertiary amine less basic than primary and secondary amines in aqueous solution. However, the electron-releasing effect does make the tertiary amine more basic than ammonia.
The reason for this;
This is not the order of basicity of these amines in aqueous solution, however. In aqueous solution the order is:
19.3A Basicity of arylamines(芳香胺的碱性)
pKb 9.42 8.92 3.36
¼îÐÔÔöÇ¿
NH2 NH2H3C NH
p- conjugate effect No p- conjugate effect
+I inductive effect
p- conjugate effect
19.3C Aminium salts and quaternary ammonium salts
( 胺盐和季胺盐)When primary, secondary, and tertiary amines act as bases and react with acids, they form compounds called aminium salts.
CH3CH2NH2 + HCl CH3CH2NH3Cl-+
(CH3CH2)2NH + HCl (CH3CH2)2NH2Cl-+H2O
H2O
(CH3CH2)3N + HI (CH3CH2)3NH l-+H2O
Triethylaminium iodide
Diethylaminium chloride
Ethylaminium chloride
(an amine salt)
When the central nitrogen atom of a compound is positively charged but is not attached to a hydrogen atom the compound is called
Quaternary ammonium hydroxides, however, are strong bases. As solids, or in solution, they consist entirely of quaternary ammonium cations (R4N+) and hydroxide ions (OH-); they are, therefore, strong bases---as strong as sodium or p
19.5B Preparation of amines through reduction of nitro
HNO3
H2SO4
NO2 NH2
1) H2 / Ni
[ H ]
Reduction methods;
2) Fe, HCl. NaOH
NO2NO2
NO2NH2
H2S
NH3, CH3CH2OH
m-Dinitrobenzene m-Nitroaniline
( 70 - 80 %)
用硫化氢( hydrogen sulfide) 还原二硝基苯,只还原一个硝基。
19.5C Preparation of amines through reductive amination
O
R'
R
Aldehyde or Ketone
NH3
[ H ]R C
H
R'
NH2 (1o Amine)
R CH
R'
NH R''R''NH2
[ H ]
R''R'''NH[ H ]
R CH
R'
NR''R'''
(2o Amine)
(3o Amine)
Mechanism for reductive amination
O
R'
R
Aldehyde or Ketone
R''NH2+
(H)R
R'
OH
NHR'' R
R'
NR''- H2O
Imine
R
R'
NH R''
(2o Amine)
H2
Ni
先亲核加成,然后消除,再还原的胺。
Three specific examples of reductive aminations follow:
O
H
NH3, H2, Ni
90 atm, 40 - 70oCCH2NH2
Benzylamine(89%)
Benzaldehyde
O
H
CH3CH2NH2, H2, NiCH2NHCH2CH3
N-Benzylethanamine(89%)
Benzaldehyde
LiBH3CN
OLiBH3CN
(CH3)2NH
N
CH3
CH3
CyclohexanoneN,N-Dimethylcyclohexanamine
(52-54%)
19.5D Preparation of amines through reduction of amides, oxime
s, and nitrilesN
CH2CN
140 oC
Raney Ni
CH2CH2NH2
Cyclohexanone2-Phenylethanamine
(71%)
CH3
O
CH3
N-Methylacetanilide
+ LiAlH4 N
CH3
CH2CH3
N-Ethyl-N-methylaniline
diethyl ether
2) H2O
N OHNa, CH3CH2OH
NH2
CyclihexylamineOxime
(50-60%)
19.5E Preparation of amines through the Hofmann and curtius r
earrangements1) Hofmann rearrangement or Hofmann degradation (霍夫曼重排 或霍夫曼降级) --- 制备
伯胺
R
O
NH2 + Br2 + 4NaOH RNH2 + 2NaBr + Na2CO3 + 2 H2O
O
NH2 + Br2 + 4NaOH PhNH2 + 2NaBr + Na2CO3 + 2 H2O
2 ) The Curtius rearrangement ( 库尔提斯重排) -- 制备伯胺
R
O
Cl
Acyl chloride
NaN3
R
O
N3
Acyl azide
R
O
N- N N+
R N C O
Isocyanate
H2OR NH2 + CO2
Primary amine
ÒìëæËáõ¥
H3C
O
Cl
Acyl chloride
NaN3
H3C
O
N3
Acyl azide
H2O+ CO2CH3 NH2
Methyl amine
19.7A Reactions of primary aliphatic amines with nitrous acid
Primary aliphatic amines react with nitrous acid through a reaction called diazotization (重氮化作用) to yield highly unstable aliphatic diazo
nium salts( 重氮盐) .
R NH2 + NaNO2 + 2HCl R N N X-+
Aliphatic diazonium salt(highly unstable)
R+ + X-
HNO2
(alkenes, alcohols. alkyl halides)
Ph NH2 + NaNO2 + 2HCl Ph N N X-+
Arenediazonium salt(stable if kept below 5 oC)
HNO2
5 oC+ NaX + 2 H2O
19.7C Reactions of secondary amines with nitrous acid
(CH3)2NH + NaNO2 + 2HCl
HNO2
5 oC(CH3)2N N O
Dimethylamine N-Nitrosodimethylamine( a yellow oil)
N
CH3
H
+ HCl + NaNO2 N
CH3
N O
N-Nitroso-N-methylaniline(87-93%) (a yellow oil)
HNO2
N-Methylaniline
19.7D Reactions of tertiary amines with nitrous acid
N
CH3
CH3
+ HCl + NaNO2 N
CH3
CH3
p-Nitroso-N,N-dimethylaniline(80-89%)
HNO2N,N-Dimethylaniline
8 oCON
因氮上没有氢,故在二甲氨基的苯环的对面发生亚硝化。
19.8 Replacement reactions of arenediazonium salts ( 重氮盐的取
代) Diazonium salts are highly useful intermediates in the synthesis of aromatic compounds, because the diazonium group can be replaced by any one of a number of other atoms or groups, including –F, -Cl, -
Br, -CN, -OH, and –H.
19.8A Synthses using diazonium salts
N
H
H
HCl + NaNO2 N2+
HNO2
5 oC+
N N+ Cl-
N2+
N N+ Cl-
H2O+. heatOH
CuClCl
Br
CuBr
CN
CuCN
KI
I
1) HBF4
2) heat F
H
H3PO2
19.8B The sandmeyer reaction: Replacement of the diazonium g
roup by –Cl, -Br, or -CNCH3
NH2
o-Toluidine
HCl, NaNO2
H2O 0 - 5 oC
CH3
N2ClCuCl
15-60 oC
CH3
Cl
+ N2
NH2
HBr, NaNO2
H2O 0 - 5 oC
CH3
N2 Br-
CuBr
100 oC
CH3
Br
+ N2
Cl
+
m-Bromochlorobenzene
m-Chloroaniline
19.8C Replacement by -INO2
NH2
NaNO2, H2SO4
H2O
0-5 oC
NO2
N2+HSO4
-
KI
I
NO2
p-Nitroaniline p-Iodonitrobenzene
+ N2
19.8D Replacement by -FCH3
NH2
m-Toluidinem-Methyl aniline
1) NaNO2, H2SO4
2) HBF4
CH3
N2+BF4
-
heat
CH3
F
m-Fluorotoluene
(69%)
19.8E Replacement by -OH
H2O100 oC
NH2
NO2
m-Nitroaniline
1) NaNO2, H2SO4
N2+HSO4
-
NO2
OH
NO2
m-Nitrophenol
(74-79%)
H2O
0-5 oC
+ N2H2SO4
19.8F Replacement by -H ( Deamination by diazotization) 通过重氮化脱氨基)
NH2
NaNO2, HCl
H2O(0-5 oC)
N2+Cl -
H3PO2
H2O25 oC
H
+ N2
CH3 CH3
Br
NaNO2, HCl
H2O(0-5 oC)
N2+Cl -
H3PO2
H2O25 oC
CH3
NO2
CH3
HNO3
H2SO4
Fe, HCl
CH3
NH2
CH3
(CH3CO)2O
CH3
NHCOCH3
Br2
FeBr3
CH3
NHCOCH3
Br
H2O, OH-
CH3
NH2
BrBr
CH3
Br
Toluene
p-Toluidine amino group is protected
removing protecting group m-Bromotoluene
Arenediazonium salt
19.9 Coupling reactions of arenediazonium salts
( 重氮盐的偶联反应)Arenediazonium ions are weak electrophiles: they react with highly reactive aromatic compounds—with phenols and tertiary arylamines—to yield azo compounds. This electrophilic aromatic substitution is often called a diazo coupli
ng reaction( 偶氮化合物) .
N NX-+
+R
R = -NR2, or -OH
N N R
N NX-+
+OH
N N OH
BenzenediazoniumChloride
Phenol
p-(phenylazo)phenol(orange solid)
¶Ô-±½Öصª»ù±½·Ó
0 oC
N NX-+
+N(CH3)2
N N N(CH3)2
BenzenediazoniumChloride
N,N-Dimethyl-p-(phenylazo)aniline(yellow solid)
N,N-¶þ¼×»ù-¶Ô±½Öصª»ù±½°·
0 oC
N,N-Dimethylaniline
CH3COONa
N NX-+
+
N N
BenzenediazoniumChloride
4-Methyl-2-(phenylazo)phenol
4-¼×»ù-2-±½Öصª»ù±½·Ó
0 oC
NaOH
OH
CH3
OH
CH3
(p-cresol)
4-Methylphenol
NaO3S N N N(CH3)2
Ëá¼îµÎ¶¨Ö¸Ê¾¼Á--¼×»ù³È
NH2HO3SNaNO2, HCl
0 - 5 oCN NX-+
HO3S
NaO3S N N N(CH3)2
N(CH3)2
NaOH
NaO3SHN N N(CH3)2
H+OH-
+
red color
yellow color
Synthesis of methyl orange 甲基橙的合成
甲基橙的变色范围 3.1-4.4
19.10 Reactions of amines with sulfonyl chlorides
( 胺与磺酰氯的反应)Primary and secondary amines react with sulfonyl chlorides to form sulfonamides ( 磺酰胺)