Nitrogen Compounds

Question 1

What constitutes an amine compound?

Answer 1

At least 1 nitrogen atom must be bonded to a carbon atom.

Question 2

Why are amines basic?

Answer 2

Their nitrogen atom contains a lone pair of electrons

This makes them H+/proton acceptors

Question 3

Why are amines soluble?

Answer 3

They can form hydrogen bonds with water molecules.

Question 4

What physical characteristics do solutions of amines show?

Answer 4

They are volatile liquids at RT with pungent smells.

Question 5

Why are amines good nucleophiles?

Answer 5

They have a lone pair of electrons which means they are attracted to electron deficient centres (+ve charges)

Question 6

How do we name primary amines?

Answer 6

Suffix ‘-ylamine’

Question 7

How do we name secondary amines?

Answer 7

Using N- as the position indicator for substituent groups.

Question 8

How do we name primary amines with -NH2 attached partway along a large carbon chain, as a substituent?

Answer 8

Positional indicator followed by amino- prefix

Question 9

What product is formed when an amine reacts with an acid?

Answer 9

Amines are basic
Thus this is an acid-base reaction
A salt is formed with a +ve nitrogen atom

Question 10

Why is the reaction between an amine and an acid NOT a neutralisation?

Answer 10

Though this is an acid-base reaction
No water is formed
Thus not neutralisation

Question 11

Give an alternative name for an optical isomer.

Answer 11

Enantiomer.

Question 12

What is an optical isomer?

Answer 12

Molecules that form non-superimposable mirror images of one another. Has a chiral centre.

Question 13

What bond shape forms around a chiral centre?

Answer 13

Tetrahedral

Question 14

What is chirality?

Answer 14

Molecules are chiral if 4 different groups are attached to a single carbon atom.

Question 15

Give na example of a nitrogen compound that displays chirality.

Answer 15

Amino acids

Question 16

What physical property dominates the reactions of amines?

Answer 16

Their lone pair

Question 17

What type of reaction mechanism will an amine typically undergo?

Answer 17

Nucleophilic substitution.

Question 18

Describe a mechanism for nucleophilic addition.

Answer 18

2-step…
RBr + NH3 -> RNH3+Br-
RNH3+Br- + NaOH -> RNH2 + NaBr + H2O
Ammonia must be dissolved in ethanol

Question 19

Why is the nucleophilic substitution of ammonia a two step mechanism?

Answer 19

Addition of NaOH directly will result in the formation of an alcohol
Since :OH- is a good nucleophile

Question 20

Why does the nucleophilic substitution of ammonia not produce a pure product?

Answer 20

The nitrogen atom on the product still has a lone pair
Further substitution can occur to form secondary, tertiary and quaternary amines

Question 21

What constitutes an amino acid?

Answer 21

Amine and carboxylic acid group

Question 22

What is an alpha amino acid?

Answer 22

NH2 is bonded to the second (alpha) carbon

Question 23

What functional groups do amino acids have? How does this affect its properties?

Answer 23

-NH2 accepts protons so is basic
- COOH donates protons so is weakly acidic (note reversible)

Question 24

What is a zwitterion?

Answer 24

Double-charged species formed by amino acids where NH2 forms NH3+ and COOH forms COO-
No overall charge but both ends are oppositely charged AT ISOELECTRIC POINT

Question 25

Why are zwitterions soluble?

Answer 25

They are charged species So dissolve in pollar solvents

Question 26

What happens to zwitterions as we... 1. decrease pH 2. increase pH

Answer 26

1. Excess of H+ means COOH and NH3+ groups form 2. Lack of H+ means COO- and NH2 groups form

Question 27

How can we synthesise polyesters?

Answer 27

Reacting many of one monomer with -OH, -COOH groups Reaction diols and dicarboxylic acids

Question 28

Why are polymers so strong?

Answer 28

Hydrogen bonds form along the length of the chain

Question 29

What is an amide linkage group?

Answer 29

C=O, N-H

Question 30

How can we synthesise polyamides?

Answer 30

Reacting one type of monomer with NH2, COOH groups Reacting diamines and dicarboxylic acids

Question 31

What type of reaction is polymerisation to form polyesters/polyamides?

Answer 31

Condensation polymerisation Water molecule is released

Question 32

What happens when we hydrolyse a polymer under acidic conditions?

Answer 32

C-O or C-N single bond is broken Resulting molecules are protonated

Question 33

What happens when we hydrolyse a polymer under basic conditions?

Answer 33

C-O or C-N single bond is broken Resulting molecules are deprotonated (-ve or lack H+)