1. Chapter 15
Amines

2. Structure & Classification
Amines are classified as 1°, 2°, or 3° depending on the number of carbon groups bonded to nitrogen

3. Structure & Classification
heterocyclic amine: an amine in which the nitrogen atom is part of a ring

4. Nomenclature IUPAC names Similar to alcohols
drop the final -e of the parent alkane and replace it by -amine
use a number to locate the amino group on the parent chain

5. Nomenclature IUPAC names (cont’d)
IUPAC nomenclature retains the common name aniline for C6H5NH2, the simplest aromatic amine
use numbers to locate substituents or, alternatively, use the prefixes ortho (o), meta (m), and para (p)
common names are still widely used

6. Nomenclature IUPAC names (cont’d)
name unsymmetrical secondary and tertiary amines as N-substituted primary amines
take the largest group bonded to nitrogen as the parent amine
smaller group(s) are substituents indicated by using the prefix N

7. Nomenclature Common names
for most aliphatic amines, list the groups bonded to nitrogen in alphabetical order in one word ending in the suffix -amine

8. Nomenclature Amine salts
when four things are bonded to a nitrogen atom, the nitrogen bears a positive charge
name the compound as a salt
replace the ending -amine (or aniline or pyridine or the like) by -ammonium (or anilinium or pyridinium or the like) and add the name of the anion

9. Physical Properties
Like ammonia, low-molecular-weight amines have very sharp, penetrating odors
trimethylamine, for example, is the pungent principle in the smell of rotting fish
two other particularly pungent amines are 1,4-butanediamine (putrescine) and 1,5-pentanediamine (cadaverine)

10. Physical Properties Amines are polar compounds
both 1° and 2° amines have N-H bonds, and can form hydrogen bonds with one another

11. Physical Properties
an N-H---N hydrogen bond is weaker than an O-H---O hydrogen bond
compare the boiling points of ethane, methanamine, and methanol

12. Physical Properties
all classes of amines form hydrogen bonds with water and are more soluble in water than are hydrocarbons of comparable molecular weight
most low-molecular-weight amines are completely soluble in water
higher-molecular-weight amines are only moderately soluble in water or are insoluble

13. Basicity of Amines
Like ammonia, amines are weak bases, and aqueous solutions of amines are basic
the acid-base reaction between an amine and water involves transfer of a proton from water to the amine

14. Basicity of Amines
The base dissociation constant, Kb, for the reaction of an amine with water has the following form, illustrated for the reaction of methylamine with water to give methylammonium hydroxide
pKb is defined as the negative logarithm of Kb

15. Basicity of Amines aliphatic amines SS bases than NH3
aromatic amines are weaker bases

16. Basicity of Amines
We can determine which form of an amine exists in body fluids, pH 7.40
if an aliphatic amine is dissolved in blood, it is present predominantly as its protonated (conjugated acid) form

17. Reactions of Amines
The most important chemical property of amines is their basicity
amines, whether soluble or insoluble in water, react quantitatively with strong acids to form water-soluble salts

18. Reactions of Amines
example: complete each acid-base reaction and name the salt formed

19. Reactions of Amines
example: complete each acid-base reaction and name the salt formed
solution:

20. Synthesis of Amines
1) Alkyl halides react with ammonia to make primary amines
This can lead to multiple amination products
Example on board
2) Alkyl halides may be reacted with cyanide and then hydrogenated to for the primary amine exclusively.

21. Reactions of Amines
3) Aldehydes and ketones can condense with primary amines and then be hydrogenated to for secondary amines
Example on the board

22. Amines
End
Chapter 16