Amines

Question 1

Name this compound:

Answer 1

2-aminopropanoic acid

Question 2

Name this compound:

Answer 2

propanamine

Question 3

Stereochemistry of tertiary and quarternary amines.

Answer 3

3° amines can be chiral. But they are always racemic because of spontaneous inversions at room temperature.

Even protonated 3° amines undergo inversion because the proton comes on and off in an acid-base equilibrium.

4° amines can be chiral and they stay chiral because they don’t undergo inversion.

Question 4

IR peaks of primary amines

Answer 4

2 peaks around 3300 cm-1

Question 5

IR peaks of secondary amines

Answer 5

1 peak around 3300 cm-1

Question 6

Amide Formation Reaction

Answer 6

Amine and an acid derivative with a good leaving group create an amide.

Question 7

Reaction of an amine with nitrous acid (HNO₂)

Question 8

Why can the nitrogen in nitrous acid be attacked?

Answer 8

The NO+ species is a very good electrophile.

Question 9

Alkylation of Amines

Question 10

Hoffmann Elimination

Answer 10

• amine + methyl iodide → exhaustive methylation of the amine → elimination with the methylated amine as leaving group
• Forms less substituted double bond.

Question 11

Basicity of amines

Answer 11

Amines like to gain protons, although neutral amines are not very likely to give up protons. Protonated amines are much more acidic.

Question 12

Basicity of amides

Answer 12

An amide, however, can lose a proton much more easily. This is because the carbonyl group next to the nitrogen contributes to a resonance structure that places the negative charge on the oxygen. Thus, the negative charge of the conjugate base is distributed over both nitrogen and oxygen

Question 13

Stabilization of adjacent carbonium ions

Answer 13

The nitrogen of the amine donates its lone electron pair to the adjacent carbonium ion

Question 14

Effect of electron donating group on aromatic amine

Answer 14

Electron donating groups on the aromatic amine increase the basicity of aromatic amines. This is because the electron donating groups contribute to the electron density on the nitrogen

Question 15

Effect of electron withdrawing group on amines

Answer 15

Electron withdrawing groups on the aromatic amine decrease the basicity of aromatic amines. This is because the electron withdrawing groups steal electron density from the nitrogen.

Question 16

Effect of ortho substituent group on aromatic amine

Answer 16

Anything ortho to the amine, no matter whether it is electron donating or withdrawing, will decrease the basicity of the aromatic amine. This is because of the ortho effect, which is basically sterics. The protonated amine will have a greater steric interaction with the ortho group, so it will be less stable.

Question 17

Aromatic amines versus alipathic amines in terms of basicity

Answer 17

Aromatic amines are weaker bases than aliphatic amines. This is because the amine donates its electron density to the aromatic ring. Also, the amine forms stable resonance structures with the aromatic ring, which is absent once the amine becomes protonated