Title: 22.15 Nitrosation of Alkylamines
122.15Nitrosation of Alkylamines
2Nitrite Ion, Nitrous Acid, and Nitrosyl Cation
3Nitrosyl Cation and Nitrosation
4Nitrosyl Cation and Nitrosation
5Nitrosation of Secondary Alkylamines
- nitrosation of secondary amines gives an
N-nitroso amine
6Example
NaNO2, HCl
H2O
(88-90)
7Some N-Nitroso Amines
8Nitrosation of Primary Alkylamines
- analogous to nitrosation of secondary amines to
this point
9Nitrosation of Primary Alkylamines
R
H
- this species reacts further
10Nitrosation of Primary Alkylamines
- nitrosation of a primary alkylamine gives an
alkyl diazonium ion - process is called diazotization
11Alkyl Diazonium Ions
- alkyl diazonium ions readily lose N2 to give
carbocations
12Example Nitrosation of 1,1-Dimethylpropylamine
13Nitrosation of Tertiary Alkylamines
- There is no useful chemistry associated with the
nitrosation of tertiary alkylamines.
1422.16Nitrosation of Arylamines
15Nitrosation of Tertiary Arylamines
- reaction that occurs is electrophilic aromatic
substitution
16Nitrosation of N-Alkylarylamines
- similar to secondary alkylamines
- gives N-nitroso amines
NaNO2, HCl,H2O, 10C
17Nitrosation of Primary Arylamines
- gives aryl diazonium ions
- aryl diazonium ions are much more stable
thanalkyl diazonium ions - most aryl diazonium ions are stable under the
conditions of their formation (0-10C)
18Example
HSO4
19Synthetic Origin of Aryl Diazonium Salts
2022.17Synthetic TransformationsofAryl Diazonium
Salts
21Transformations of Aryl Diazonium Salts
22Preparation of Phenols
H2O, heat
23Example
1. NaNO2, H2SO4 H2O, 0-5C
2. H2O, heat
(73)
24Transformations of Aryl Diazonium Salts
25Preparation of Aryl Iodides
- reaction of an aryl diazonium salt with potassium
iodide
KI
26Example
I
1. NaNO2, HCl H2O, 0-5C
Br
2. KI, room temp.
(72-83)
27Transformations of Aryl Diazonium Salts
28Preparation of Aryl Fluorides
- heat the tetrafluoroborate salt of a diazonium
ion - process is called the Schiemann reaction
29Example
1. NaNO2, HCl, H2O, 0-5C
2. HBF4
3. heat
(68)
30Transformations of Aryl Diazonium Salts
31Preparation of Aryl Chlorides and Bromides
- aryl chlorides and aryl bromides are prepared by
heating a diazonium salt with copper(I) chloride
or bromide - substitutions of diazonium salts that use
copper(I) halides are called Sandmeyer reactions
32Example
NH2
Cl
1. NaNO2, HCl, H2O, 0-5C
2. CuCl, heat
NO2
NO2
(68-71)
33Example
1. NaNO2, HBr, H2O, 0-10C
Br
Cl
2. CuBr, heat
(89-95)
34Transformations of Aryl Diazonium Salts
35Preparation of Aryl Nitriles
- aryl nitriles are prepared by heating a diazonium
salt with copper(I) cyanide - this is another type of Sandmeyer reaction
36Example
1. NaNO2, HCl, H2O, 0C
CN
CH3
2. CuCN, heat
(64-70)
37Transformations of Aryl Diazonium Salts
38Transformations of Aryl Diazonium Salts
- hypophosphorous acid (H3PO2) reduces diazonium
salts ethanol does the same thing - this is called reductive deamination
39Example
NaNO2, H2SO4, H3PO2
(70-75)
40Value of Diazonium Salts
- 1) allows introduction of substituents such as
OH, F, I, and CN on the ring - 2) allows preparation of otherwise difficultly
accessible substitution patterns
41Example
4222.18Azo Coupling
43Azo Coupling
- Diazonium salts are weak electrophiles.
- React with strongly activated aromatic compounds
by electrophilic aromatic substitution.
44Example
Cl
45Section 22.19Spectroscopic Analysis of Amines
46Infrared Spectroscopy
- the NH stretching band appears in the
range3000-3500 cm-1 - primary amines give two peaks in this region,
onefor a symmetrical stretching vibration, the
other foran antisymmetrical stretch
47Infrared Spectroscopy
- primary amines give two NH stretching peaks,
secondary amines give one
481H NMR
- compare chemical shifts in
4913C NMR
- Carbons bonded to N are more shielded than those
bonded to O.
CH3NH2
CH3OH
50UV-VIS
An amino group on a benzene ring shifts ?maxto
longer wavelength. Protonation of N causesUV
spectrum to resemble that of benzene.
?max204 nm256 nm
?max230 nm280 nm
?max203 nm254 nm
51Mass Spectrometry
- Compounds that contain only C, H, and O have
even molecular weights. If an odd number of N
atoms is present, the molecular weight is odd. - A molecular-ion peak with an odd m/z value
suggests that the sample being analyzed contains
N.
52Mass Spectrometry
- Nitrogen stabilizes carbocations, which drives
the fragmentation pathways.
e
53Mass Spectrometry
- Nitrogen stabilizes carbocations, which drives
the fragmentation pathways.
e
54End of Chapter 22