AMINES

Naming

• How many chains are coming off the Nitrogen atom in the amine

• Count the number of carbons in each chain• Name each chain as a branch• Add the word amine after the branch(es)

Name the following• CH3NH2

• CH3CH2CH2CH2NH2

• CH3NHCH3

• CH3CH2NHCH3

• (CH3)3N

1 C in branch Hence MethylHence Methylamine

1C in each branch Hence dimethylHence dimethylamine

4C in branch Hence ButylHence Butylamine

1C in first branch and 2 C in second branchHence EthylmethylHence Ethylmethylamine

1C in all three first branchesHence trimethylHence trimethylamine

Primary Secondary and Tertiary

• Count the number of branches off the Nitrogen in the amine

• Only 1C =• If 2C =• If 3 C =

Primary amine

Secondary amine

tertiary amine

Primary

Primary

Secondary

Tertiary

Structure of amines

What are these?

What is the bond angle?

Lone Pair

107.5O

What chemistry do we expect?

Charge here on C

Charge here on N

BP/MP?

• What can form between two Amine molecules?

• Can you draw it?

• What does this mean in terms of properties

A hydrogen bond

MP/Bp are higher than expected because the intermolecular force (H-Bond) is stronger than a typical VDW so more energy si required to break them.

Preparation of amines• Nucleophilic substitution reaction between

Ammonia and Halogenoalkanes dissolved in ethanol

• Write the equation for the formation ofa. CH3NH2

b. CH3CH2NH2

c. CH3NHCH3

CH3Cl + 2NH3 CH3NH2 + NH4Cl in ethanol

CH3CH2Cl + 2NH3 CH3CH2NH2 + NH4Cl in ethanol

2CH3Cl + 3NH3 CH3NHCH3 + 2NH4Cl in ethanol

NB: Amines will react with halogenoalkanes as well to form secondary aminesThe by product HCl will also react with ammonia to form Ammonium Chloride

Click here for mechanism for the above reactions

Water soluble?• What can form between two Amine molecules?

• What can form between two water molecules?

• What can form between an amine and a water molecule

• Can you draw them?

A hydrogen bond

A hydrogen bond

A hydrogen bond

The ability to form H-bonds with the water molecules means that amines dissolve in water

Acid or Base?• What is present on the Nitrogen of the amine?

• What will be attracted to a Nitrogen atom?

• What can happen next?

A lone pair AND a slight negative charge

A hydrogen ions

The lone pair of electrons on the Nitrogen are donated to the H+ ion forming a dative covalent bond

The ability accept an H+ ion means that Amines are BASES

Equations for base behaviour• Addition of water

• Addition of H+

• Addition of HCl

• Addition of H2SO4

RNH2 + H2O RNH3+ + OH-

RNH2 + H+ RNH3+

RNH2 + HCl RNH3+ + Cl-

2RNH2 + H2SO4 2RNH3+ + SO4

-2

Other reactions of amines

• What might happen when you add amines toa. Iodomethane (or other halogenoalkanes)

b. Acetyl Chloride (CH3COCl)

Substituted amines will form

CH3I + 2RNH2 RNHCH3 + RNH3I

Amides will form

CH3COCl + 2RNH2 RNHCOCH3 + RNH3I

Phenylamine

Questions to askHow is this molecule formed?What is the chemistry of this molecule?Why?

Preparation- How?

• Reduction of Nitrobenzene using Sn and Conc HCl

• Can you write an equation?

+ 6[H]+ 2H2O

Reactions of Phenylamine

• Where will the lone pair be on the Nitrogen?

• How does this effect the basic nature of phenylamine

• Why?

Incorporated into the pi cloud of the benzene ring. The p orbital on the Nitrogen overlaps with the P orbitals on the benzene ring

Makes phenylamine less basic

The lone pair is longer available to donate to an H+ so phenylamine does not accept a proton as readily as other amines

Reactions of the benzene ring in Phenylamine

What will be the effect on the electron density in the ring?

Electron density will increase.Phenylamine will be able to polarise molecules or attract an electrophile

What reactions will Phenylamine undergo?

C6H5NH2 + 3Br2 C6H2Br3NH2 + 3HBrC6H5NH2 + dil HNO3 C6H2(NO2)3NH2 + 3H2O

NB THESE ARE SIMILIAR REACTIONS TO PHENOL

Ammonia with bromoethane

EthylamineCH3CH2Br + NH3 CH3CH2NH2 + HBr

Preparation of amines

Further reactions with bromoetane

DiethylamineCH3CH2Br + CH3CH2NH2 CH3CH2NHCH3CH2 + HBr

mechanism

mechanism

NB The HBr will be neutralised by excess ammonia or amine to form NH4Cl or RNH3Cl respectively but I wouldn’t include in a mechanism only the balanced equation

δ+ δ-CH3

H

BrC

H Br-

Ammonia with bromoethane

Nucleophilic substitution mechanism

ethylamineCH3

H

NH2C

HHBr

Will go to NH3Br with excess ammonia

reaction equation

N H

H H

CH3

H

NC

H

H

H

+H

δ+ δ-CH3

H

BrC

H Br-

Further reactions with bromoethane

Nucleophilic substitution mechanism

Diethylamine HBrWill go to RNH2Br with excess

amine

reaction equation

N H

H CH3CH2

CH3

H

NC

H

H

H

+CH3CH2

CH3

H

NHC

H

CH3CH2

δ+ δ-CH3

H

BrC

H Br-

Further reactions with bromoethane

Nucleophilic substitution mechanism

triethylamineHBr

Will go to RNH2Br with excess aminereaction equation

N CH3CH2

H CH3CH2

CH3

H

NC

H

CH3CH2

H

+CH3CH2

CH3

H

NC

H

CH3CH2

CH3CH2