3.11 Amines

Question 1

How do you name amines

Answer 1

amine or amino

Question 2

Why are amines so reactive

Answer 2

The lone pair of electrons on the nitrogen - due to polar N-H bond

Question 3

What shape are amines around the N? Bond angle?

Answer 3

Trigonal pyramidal, 107 degrees due to lone pair on N

Question 4

What kind of IMF do they have and why

Answer 4

Hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom

Question 5

Do amines have imf which are stronger than or weaker than alcohols? Why?

Answer 5

Weaker, as N has a lower electronegativity than O —> weaker hydrogen bonding

Question 6

What state are amines at 298K

Answer 6

Short chains are gases, longer chains are volatile liquids

Question 7

What do they smell of, why

Answer 7

Fishy smell - rotting fish/flesh releases di- and triamines

Question 8

Which primary amines are soluble in water/alcohols why

Answer 8

Up to 4 carbon atoms, as they can hydrogen bond to water molecules. After this, non-polarity of hydrocarbon chains makes them insoluble

Question 9

What kind of solvents are most other amines soluble in

Answer 9

Less or non-polar solvents

Question 10

Solubility of phenylamine, why

Answer 10

Not very soluble due to the non-polarity of the benzene ring - C6H5 cannot form hydrogen bonds

Question 11

How can/when do amines act as bases

Answer 11

When they bond with a H+ ion

Question 12

How can/when do amines act as nucleophiles

Answer 12

When they bond with an electron deficient C atom (donate lone pair from N)

Question 13

Draw a mechanism for the basic action of an amine with water

Answer 13

Google

Question 14

What is the product from the basic action of an amine with water

Answer 14

RNH3+ ammonium ion, which forms a salt with an anion

Question 15

Is ammonium ion soluble in water

Answer 15

Yes as its ionic so attracted to the polar bonds in H2O

Question 16

How could you regenerate the soluble amine from the ammonium salt

Answer 16

Add a strong base (NaOH) –> removes H+ ions from ammonium ion

Question 17

In order to be the strongest base, what must a particular amine have (out of a set of amines)

Answer 17

Greatest electron density around the N atom, making it a better electron pair donor (attracts protons more)

Question 18

What does positive/negative inductive effect mean

Answer 18

Positive inductive effect = donate electrons, increase density around N
Negative means remove electrons, decrease density around N

Question 19

What effect do alkyl groups have on electron density and base strength

Answer 19

Positive inductive effect - increase electron density around N - stronger base

Question 20

What effect do aryl groups have on electron density and base strength

Answer 20

Negative inductive effect - decrease electron density around N - weaker base

Question 21

Why are tertiary amines never good bases

Answer 21

Insoluble in water

Question 22

Draw a mechanism for the nucleophilic substitution of NH3 with RCH2Br to form primary amines

Answer 22

Google

Question 23

How can primary amines then form secondary, tertiary etc

Answer 23

Multiple substitutions; primary amine is a nucleophile that attacks the original haloalkane etc

Question 24

What are the problems with this method

Answer 24

Not efficient as low yield of primary amine due to multiple substitutions

Question 25

How do you get from a nitrile to a primary amine (name of reaction type and reagents/catalysts)

Answer 25

Reduction using Nickel / hydrogen catalyst

Question 26

What mechanism is used for forming amides from acyl chlorides and amines

Answer 26

Nucleophilic addition / elimination

Question 27

Draw a mechanism for the reaction of ethanoyl chloride with ethanamine

Answer 27

google