Chapter Fifteen

Amines

2

Goals1.  Recognize primary, secondary, tertiary, and

heterocyclic amines– Recognize quaternary ammonium ions.

2.    Name simple amines & write their structures, 3. Describe amines in terms of hydrogen bonding,

solubility, boiling point, and basic nature4.    Be able to predict the products of the acid–base

reactions of amines and ammonium ions.5.  Describe properties of typical of amines.

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Amines

A compound that has one or more organic groups bonded to nitrogen:

The importance of the NH4+ ion

• Each amine N atom has a lone pair of electrons. – This lone pair is

responsible in large part for the chemistry of amines.

• When a fourth group bonds to the nitrogen through this lone pair a quaternary ammonium ion, which has a permanent positive charge and forms ionic compounds with anions.

Amines are Basic

Amines exist as ammonium ions in blood and other body fluids resulting in high pH.

aromatic amine ammonia non-aromatic amines

Strength of the base

Amines are Basic

• Because of the basic nature, they are often referred to as Alkaloids

• Man has a long history of extracting amines from plants for medicinal and recreational uses

Codein: A heterocyclic amine

Protein contains amine groups– Volatile amines produced during decay are responsible

for the odor of rotten fish or decaying meat. – Cadaver-sniffing dogs are used to detect the strong

odor of the amines produced from decaying flesh.

Some complex amines from plants can be very poisonous. Many useful drugs are amines.

Pharmaceutical Amines Diphenhydramine is an over-the-counter antihistamine.

Antihistamines of this type are oily liquid, and are converted to amine salts to be used formulated for use as medicine

Diphenhydrammonium chloride is also called Diphenhydramine hydrochloride

Naming Primary Amines1. Identify the alkyl group attached to nitrogen – Add the suffix -amine to the alkyl group name

Secondary and Tertiary Amine

Named by adding di- or tri-, to the alkyl group name along with the suffix -amine.

Dipropylamine Triethylamine

Classify the amine shown below as primary, secondary, tertiary, or quaternary.

 Primary

 Secondary

 Tertiary

 Quaternary

0% 0%10%

90%

1. Primary2. Secondary3. Tertiary4. Quaternary

Countdown

10

Complex 2o and 3o Amines• The parent compound is chosen as the 1 amine that

contains the largest of the R groups.• All other groups are are treated as N-substitute groups

•2. It has a ethyl R group :

• The largest chain is propane thus the compound is a propylamine

we call it N-Ethylpropylamine

Name the amine shown below.

CH3CH2NCH2CH2CH3|CH3

  N-ethyl, N

-methylpro...

  N-ethyl, N

-propylm

et...

  N-methyl, N-pentylamine

  N-methyl, N-propylet...

45%

18%

27%

9%

1. N-ethyl, N-methylpropylamine 2. N-ethyl, N-propylmethylamine3. N-methyl, N-pentylamine4. N-methyl, N-propylethylamine

Countdown

10

Who am I?

  N-ethyl-N-met...

 N-methyl-N-eth...

  N-hexyl-N-met...

  N-ethyl-N-met...

0%

75%

0%

25%

1. N-ethyl-N-methyl-N-hexyl amine 2. N-methyl-N-ethyl hexylamine 3. N-hexyl-N-methyl ethyl amine 4. N-ethyl-N-methylhexyl amine

Who am I?

1. N-ethyl-N-methyl-N-hexyl amine 2. N-methyl-N-ethyl hexylamine 3. N-hexyl-N-methyl ethyl amine 4. N-ethyl-N-methylhexyl amine

Aromatic Amine’s• The simplest aromatic amine

is known by the common name aniline.

• The methy group is treated as a substitution onto the Aniline

Amino Group

• –NH2 is also a functional group (amino group)

• when this group is treated as a substituent amino- is used as a prefix. 3-Aminopropanoic acid

Properties of AminesThe lone electron pair on the N in amines causes amines to be weak bases:

.

Electron pair donors that form a bond with H+ in water

Physical Properties• Because of hydrogen bonding, 1 and 2 amines have higher boiling points than

alkanes of similar size.– Amines have less hydrogen bonding, and lower boiling than alcohols of similar size. 

• All amines can hydrogen-bond to water molecules through the lone electron pair on their nitrogen atoms. – Amines with up to about 6 C’s are soluble in water.

3 amine molecules have no H atoms attached to N and therefore cannot hydrogen-bond with each other. As a result they are much lower boiling than alcohols or 1 or 2 amines of similar molecular weight.

Heterocyclic Nitrogen Compounds• Heterocycle: A ring that contains nitrogen or some

other atom in addition to carbon in the ring structure • Heterocycles are common in many natural compounds found in

plants and animals.

Heterocyclic Nitrogen compounds

• Look for # of nitrogen atoms and # of carbon atoms

This compound has 2 nitrogen atoms and 4 carbon atoms

Heterocyclic Nitrogen compounds

• Look for # of nitrogen atoms and # of carbon atoms

This compound has 4 nitrogen atoms, and 5 carbon atoms

Basic Nature of Amines

• Amines exist as ammonium ions in the aqueous environment of blood and other body fluids, which typically have a pH value of 7.2

• When you see amine compounds represented – they are normally shown as ions.

Amines are Basic

Amines exist as ammonium ions in blood and other body fluids resulting in high pH.

aromatic amine ammonia non-aromatic amines

Strength of the base

Naming Amine ions• The positive ions formed by addition

of H+ to alkylamines are named by replacing the ending –amine

• by -ammonium.

To name the ions of heterocyclic amines, the amine name is modified by replacing the -e with -ium.

Amine Salts

• Composed of an ammonium cation and an anion– Ammonium salts are generally odorless, white, crystalline solids that are

much more water-soluble than neutral amines because they are ionic.

Permant + charge structures in solution that are are unaffected by changes in pH.

Quaternary ammonium ions

Benzalkonium chlorides, used in surgical scrubs and storage of surgical instruments have both antimicrobial and detergent properties.

Amines in Plants: Alkaloids1. Naturally occurring, nitrogen-containing compound

isolated from a plant2. Usually basic, bitter, and poisonous3. The bitterness and poisonous nature of alkaloids probably

evolved to protect plants from being devoured by animals.

Physiologically Active Alkaloids• Caffeine and nicotine are stimulants. • Others are notable as pain relievers

(analgesics), as sleep inducers, and for the euphoric states they can create.