11: Amines

Question 1

Give the formula of an ammonium ion.

Answer 1

NH4+

Question 2

Give the shape of an ammonium ion.

Answer 2

Tetrahedral

Question 3

What is formed when a hydrogen in ammonia is replaced by an alkyl or aromatic group?

Answer 3

Amine

Question 4

If one hydrogen in ammonia is replaced with a different organic functional group, what is formed?

Answer 4

Primary amine

Question 5

If two hydrogens in ammonia is replaced with a different organic functional group, what is formed?

Answer 5

Secondary amine

Question 6

If three hydrogens in ammonia are replaced with a different organic functional group, what is formed?

Answer 6

Tertiary amine

Question 7

What does the NH2 functional group smell of?

Answer 7

Rotten fish

Question 8

Generally how do we name amines?

Answer 8

Amine is the suffix, the prefix depends on the organic groups attached

Question 9

Give 2 uses of amines.

Answer 9

Used in drugs to treat malaria
Used to make plastics

Question 10

Give a use of quaternary amine salts.

Answer 10

To make detergents.

Question 11

Why are amines considered bronsted-lowry bases?

Answer 11

They accept protons by forming a coordinate bond with them.

Question 12

When acids react with amines, what is produced?

Answer 12

Salt

Question 13

What does the strength of amines as bases depend on?

Answer 13

The availability of the lone pair on the nitrogen.

Question 14

Are primary aromatic amines strong or weak bases? Why?

Answer 14

Weak
The benzene ring draws electrons towards itself and the nitrogen’s lone pair gets partially delocalised onto the ring.

Question 15

Are ammonia molecules strong or weak bases? Why?

Answer 15

They are in between strong and weak. They do not have an aromatic group to pull electrons away from the amine or they don’t have an alkyl group to push the lone pair of electrons forward and make the lone pair more available.

Question 16

Are primary aliphatic amines strong or weak bases? Why?

Answer 16

Strong bases. The alkyl group pushes electrons away from itself towards the hydrogen, making them more available for a proton to bind to.

Question 17

What is an inductive effect?

Answer 17

The ability of an atom in a molecule to pull electrons towards itself, increasing the negative charge.

Question 18

Why are secondary aliphatic amines stronger bases than primary amines?

Answer 18

They have 2 inductive effects.

Question 19

Amides are derivatives of what organic molecule?

Answer 19

Carboxylic acids

Question 20

Give the formula of the group that amides contain.

Answer 20

CONH2

Question 21

In CONH2, what does the carbonyl group doto NH2’s electrons?

Answer 21

Pulls electrons away from the NH2.

Question 22

Generally, how do we name amides?

Answer 22

Amide is always the suffix.
The prefix comes from the length of the RCO chain.

Question 23

Name the mechanism that forms amines from halogenoalkanes.

Answer 23

Nucleophilic substitution

Question 24

Why are there a mixture of primary/secondary/tertiary and quaternary ammonium salts produced from nucleophilic substitution of haloalkanes?

Answer 24

More than one hydrogen in the halogenoalkane is likely to be substituted.

Question 25

Describe the mechanism of nucleophilic substitution of halogenoalkanes to produce amines.

Answer 25

1. NH3 attacks slightly positive carbon bonded to halogen.
2. Halogen breaks off as a halide ion.
3. NH3 binds and the N is positive
4. Another NH3 attacks a hydrogen bonded to the positive nitrogen and breaks off.
5. The broken off hydrogen bonds with the NH3 and produces an NH4+ ion

Question 26

Why does nucleophilic substitution keep occurring on the amine molecule produced?

Answer 26

It has a lone pair, so is still a nucleophile.

Question 27

Briefly, how can we produce amines from nitriles?

Answer 27

By reducing the nitrile using a strong reducing agent (such as LiAlH4 in dry ether), followed by dilute acid

Question 28

Why do we not use reduction of nitriles to produce amines in industry?

Answer 28

Too expensive

Question 29

Give the conditions for the production of amines from nitriles in industry.

Answer 29

Nickel or platinum catalyst
High temperature and pressure

Question 30

Name the mechanism that produces primary amides from acyl chlorides.

Answer 30

Nucleophilic addition elimination

Question 31

Describe the nucleophilic addition elimination mechanism to produce amides from acyl chloride and ammonia.

Answer 31

1. Lone pair on nitrogen in ammonia ttacks the slightly positive carbon in the acyl chloride
2. A pair of electrons from C=O is transferred onto the oxygen, so the bond is now single.
3. The pair of electrons on the oxygen reform the double bond and the Cl is removed
4. This leaves the amide ion positively charged and the Cl-
5. The Cl- bonds to a hydrogen on the N atom, the hydrogen breaks off, forming HCl
6. This leaves an amide and HCl is eliminated.

Question 32

When acid anhydrides react with primary amines, what 2 things are formed?

Answer 32

N-substituted amide and carboxylic acid

Question 33

When acid anhydrides react with ammonia, what 2 things are formed?

Answer 33

Primary amide and a carboxylic acid.

Question 34

Explain how aromatic amines a produced,

Answer 34

A mixture of a nitrocompound, tin and conc HCl is heated under reflux to produce a salt.
An alkali is added to the mixture (such as NaOH) which turns the salt into an aromatic amine.

Question 35

What are N-Substituted amides?

Answer 35

Amides where one of the hydrogens attached to nitrogen has been substituted with an alkyl group

Question 36

How do we name N substituted amides?

Answer 36

Add N-(alkyl group) for example, N-propylamide.