lecture 25 amine nomenclature basicity of amines synthesis of amines (on board)

Lecture 25

• Amine nomenclature

• Basicity of amines

• Synthesis of amines (on board)

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-

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

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

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

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

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

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

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