lecture 25 amine nomenclature basicity of amines synthesis of amines (on board)
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Lecture 25
• Amine nomenclature
• Basicity of amines
• Synthesis of amines (on board)
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Nomenclature of Aldehydes & Ketones:IUPAC Rules
Functional Group Suffix if highest priority group As a substituent
CO2H carboxylic acid -oic acid -carboxy-
CO2R ester -oate -alkoxycarbonyl-
CO2NR2 amide -amide -carbamoyl-
CHO aldehyde -al -oxo-
CRO ketone -one -oxo-
OH alcohol -ol -hydroxy-
NR2 amine -amine -amino-
SH thiol -thiol -mercapto-
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Nomenclature of Primary Amines: IUPAC
A. Primary Amines
1. Find the longest chain to contain the -NH2 group; this is the parent chain.
2. This parent chain’s name ends in ‘amine’ - the suffix. E.g., take alkane and convert to alkanamine.
3. Number the parent chain such that the carbon bearing the -NH2 has the lowest number possible. Give location of -NH2 group in name.
4. Give name; be sure to list substituents alphabetically and to give their location; these are the prefixes. Remember that sec-, tert-, o-, m-, p-,
di-, tri-, tetra- are not considered when alphabetizing, but iso is.
Name the following:
RNH2
NH2
H2N NH2
NH2
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Nomenclature of Primary Amines: Common Name
Primary Amines
If the primary amine is a simple structure, that is the carbon group is simple,then the common name is easy to determine. In the common name, the amine’s name is “alkyl amine”; two words.
Name the following:
RNH2
NH2NH2
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Nomenclature of 2° & 3° Amines: IUPAC
B. 2° & 3° Amines
1. Find the longest R group chain to contain the -NR2/-NHR group; this is the parent chain. The carbon of the parent chain that’s bound to the N gets the #1 designation.
2. This parent chain’s name ends in ‘amine’ - the suffix. E.g., take alkane and convert to alkanamine.
3. The other R groups are listed first (as the first word) and alphabetically with an “N-” in front of them to designate that the R group is bound to the nitrogen. (Similar to 2° and 3° amide nomenclature.)
4. Give name; be sure to list the parent chain substituents alphabetically and to give their location; these are the prefixes. Remember that sec-, tert-, o-, m-, p-,
di-, tri-, tetra- are not considered when alphabetizing, but iso is.
Name the following:
N R
R''
R'
R = R or H
NH
N
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Nomenclature of 2° & 3° Amines: Common Name
B. 2° & 3° Amines
1. Identify the R groups bound to nitrogen.
2. List the alkyl groups alphabetically. Remember not to alphabetize di-, tri-, sec-, or -tert.
3. End the name with the word “amine”.
Name the following:
N R
R''
R'
R = R or H
NH
N
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Nomenclature: Heterocyclic Amines
N NH
HN
NH N
H
pyridine pyrrole indole
pyrrolidine piperidine
1
2
3
4
5
6
7
1
1
11
2 2
22
3
3
33
4
4
44
5
5
5
5
6
6
Parent names of some heterocyclic amines:
Name the following:
N
CH3
CH3 HN
Cl
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Basicity of Amines
• Basicity of amines dominates its chemistry.
• Measure of basicity is pKb:
R3N: + H2OKeq
R3N-H + OH
Keq =[R3N-H] [OH]
[R3N] [H2O]
Define Kb = [H2O] Keq =[R3N-H] [OH]
[R3N]
pKb = - log Kb
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Basicity of Amines
pKb = - log Kb
• The lower the pKb value, the more basic the amine.
• pKb values are related to the pKa values of the conjugate acids:
pKa + pKb = 14
Example: NH3 has a pKb = 4.74, so the pKa of its conjugate acid, NH4
+ is 9.26.
• It is common to find the pKa for the ammonium salt; then needto convert to pKb.
• Unlike carboxylic acids, the effect of the R substituents on thenitrogen’s basicity is minimal except for aniline derivatives.
NH2
R