Organic - 3.11 Amines

Question 1

What is the structure of amines based on?

Answer 1

Ammonia, where hydrogen atoms have been replaced by alkyl or aryl groups.

Question 2

What are the hydrogen atoms replaced with in amines?

Answer 2

Alkyl or aryl groups

Question 3

What are quaternary ammonium compounds produced from?

Answer 3

Produced from tertiary amines where the nitrogen’s lone pair of electrons forms a dative covalent bond to the 4th alkyl group.

Question 4

How many alkyl groups does a quaternary ammonium salt have?

Answer 4

Four

Question 5

What is the shape of NH4+ and why?

Answer 5

Tetrahedral, four bonding pairs spread equally

Question 6

What is the shape of NH3 and why?

Answer 6

Pyramidal, lone pair exerts a stronger repulsive force

Question 7

What is the bond angle in amines?

Answer 7

107

Question 8

What prefix is used if there are two identical R groups attached to a nitrogen?

Answer 8

di-

Question 9

What prefix is used if there are three identical R groups attached to a nitrogen?

Answer 9

tri-

Question 10

How are the groups ordered if there are two different alkyl or aryl groups present?

Answer 10

They are ordered alphabetically

Question 11

When is the amine group denoted using amino-?

Answer 11

If other functional groups are present in the molecule

Question 12

What is the hierarchy used in organic chemistry?

Answer 12

1. Carboxyl (-COOH)
2. Aldehyde (-CHO)
3. Ketone (-CO-)
4. Hydroxyl (-OH)
5. Amines (-NH2, -RNH, -R2N)
6. Alkene (-C=C-)

Question 13

What do halogenoalkanes and ammonia form?

Answer 13

Amines

Question 14

What are the conditions for the preparation of primary amines from halogenoalkanes?

Answer 14

Heat in a sealed flask with excess ammonia in ethanol.

Question 15

What is the type of reaction for the preparation of primary amines from halogenoalkanes?

Answer 15

Nucleophilic Substitution

Question 16

What is the overall reaction for the preparation of primary amines from halogenoalkanes?

Answer 16

R-X + 2NH3 -> R-NH2 + NH4X

Question 17

What are the conditions for the preparation of primary amines from nitriles by reduction?

Answer 17

Using hydrogen in the presence of a nickel catalyst or by using a reducing agent such as LiAl4 in ether.

Question 18

What are the two steps involved in the preparation of primary amines from nitriles?

Answer 18

1) Formation of a nitrile from a halogenoalkane
2) Reduction of the nitrile to form an amine

Question 19

How are aromatic amines prepared?

Answer 19

Prepared by the reduction of nitro compounds

Question 20

How is phenylamine prepared?

Answer 20

By reduction of nitrobenzene using tin and conc sulfuric acid as a reducing agent

Question 21

What are the conditions for the preparation of phenylamine?

Answer 21

Heat under reflux with tin and excess sulfuric acid, followed by adding conc NaOH.

Question 22

Why is concentrated NaOH added in the preparation of phenylamine?

Answer 22

To remove the hydrogen ion from the NH3+ group. The addition of concentrated alkali liberates the free amine.

Question 23

What are aromatic amines used for?

Answer 23

Used in the manufacture of dyes (azo dyes)

Question 24

What are the two basic properties of amines?

Answer 24

Weak bases
Lone pair of electrons on nitrogen atom of ammonia and amines accept a proton.

Question 25

What are two formulas for the reaction of amines with dilute mineral acids?

Answer 25

ammonia + acid -> ammonium salt amine + acid -> alkyl ammonium salt

Question 26

What is the equation for the reaction of an amine with dilute HCl?

Answer 26

CH3NH2 + HCl -><- CH3NH3+Cl- Methylamine + hydrochloric acid -><- phenylammonium chloride (Reversible reaction)

Question 27

What is the equation for the reaction of an amine with dilute H2SO4?

Answer 27

2CH3CH2NH2 + H2SO4 -><- (CH3CH2NH3)2SO4 ethylamine + sulfuric acid -><- ethyl ammonium sulfate (Reversible reaction)

Question 28

What happens when an amine reacts with water?

Answer 28

They accept a hydrogen ion from water to produce an alkylammonium ion and hydroxide ion.

Question 29

How does base strength decrease in amines?

Answer 29

Strongest: Primary Aliphatic Amine Ammonia Weakest: Primary Aromatic Amine

Question 30

Why are primary aliphatic amines stronger bases than ammonia?

Answer 30

Because of the alkyl group attached to the nitrogen. Alkyl group is electron donating causing a lone pair to be more available

Question 31

Why are primary aromatic amines weaker bases than ammonia?

Answer 31

Weaker bases because nitrogen's lone pair of electrons can overlap with the delocalised pi electrons in the benzene ring. Lone pair is less available for accepting a proton.

Question 32

What makes amines nucleophiles?

Answer 32

They all contain a lone pair of electrons so they act as nucleophiles.

Question 33

What are the two steps in making a primary amine?

Answer 33

An amine and halogenoalkane react and initially a salt is formed. Then the salt reacts with excess ammonia to form a primary amine.

Question 34

How is a secondary amine formed from a primary amine?

Answer 34

Further substitution reactions may occur. This is because the primary amine produced has a lone pair so it can act as a nucleophile and continue to react with any unused halogenoalkane.

Question 35

How is a tertiary amine formed from a secondary amine

Answer 35

The secondary amine produced also has a lone pair so it can act as a nucleophile.

Question 36

How is a quarternary ammonium salt formed from a tertiary amine?

Answer 36

The tertiary amine reacts with the halogenoalkare to form a quarternary ammonium salt.

Question 37

What are the conditions required for a primary amine to be produced?

Answer 37

Excess ammonia

Question 38

What are the conditions needed to produce a quaternary ammonium salt?

Answer 38

Excess halogenoalkane

Question 39

What are quarternary ammonium salts used for?

Answer 39

Cationic surfactants: found in detergents, fabric softeners and hair conditioners.