6.2 Nitrogen Compounds, Polymers And Synthesis

Question 1

What is an amine?

Answer 1

Organic compounds where one or more of the hydrogens of ammonia has been replaced by an alkyl chain

Question 2

How do you name tertiary amines?

Answer 2

-Longest carbon chain as stem
-Add the other two carbons as prefixes
-If there’s more than one of the same chain use di- or tri-
Begin the name with N-, N-
-e .g . N-, N-dipropylbutamine

Question 3

Explain the basicity of amines

Answer 3

There’s a lone pair of electrons on the nitrogen atom that’s able to accept protons (H+ ions).

So they’re us.

Question 4

What is formed when amines react with dilute acid?

Example:
CH3CH2NH2 + HCl –>

ethylamine + hydrochloric acid–>

Answer 4

Neutralised to form ammonium salt

CH3CH2NH2 + HCl –> CH3CH2NH3+Cl-

ethylamine + hydrochloric acid–> ethylammonium chloride

Question 5

How are aliphatic amines made?

Answer 5

Heating a haloalkane with excess of ethanolic ammonia

Question 6

What is the problem with making aliphatic amines?

Answer 6

You get a mixture of primary, secondary, tertiary amines and Quaternary ammonium salts as more then one hydrogen likely substituted.

Can be separated via fractional distillation

Question 7

Why is excess ammonia used in making amines?

Answer 7

Drive reaction to the right forming more product

Question 8

How are aromatic amines made?

Answer 8

Made by reducing a nitro compound.

Heat a mix of nitro compound, tin metal and conc. HCl under reflux-this makes a salt.

Add sodium hydroxide to neutralise excess acid

nitrobenzene + 6[H] –> Phenylamine +2H2O

Question 9

What is the general formula for α-amino acid?

Answer 9

RCH(NH2)COOH

Question 10

How does an amino acid react with Acid?

Answer 10

Amino group reacts with acid forming a salt of the conjugate acid.

RCH(NH2)COOH + HCl —> RCH(COOH)Cl-H3N+

Question 11

How does an amino acid react with Alkali?

Answer 11

The carboxylic acid group reacts with an alkali to form a conjugate base.

This can combine with a positive ion to form a salt.

RCH(NH2)COOH + NaOH —> RCH(NH2)COO-Na+ + H2O

Question 12

What happens when an amino acid reacts with alcohols?

Answer 12

The carboxylic group reacts with alcohol in the presence of a strong acid catalyst forming an ester

Question 13

What does amphoteric mean?

Answer 13

Act as acid and base (Amino acid)

Question 14

What happens when amino acids form zwitterions?

Answer 14

the two groups exchange a proton to from internal salt

[A proton (H+) is transferred from the carboxyl group to the basic group->N becomes +]

Question 15

What is the isoelectric point?

Answer 15

the pH at which a zwitterion forms

Question 16

In acidic conditions what do amino acids form?

Answer 16

NH3+ (equilibrium driven right)

Question 17

In alkali conditions what do amino acids form?

Answer 17

COO-Na+ (equilibrium driven left)

Question 18

Define optical isomerism

Answer 18

Stereoisomers that are non-superimposable mirror images of each other about a chiral
centre

Question 19

How do you identify a chiral center?

Answer 19

Atom (carbon) with 4 different groups attached to it.

Question 20

What is a racemate?

Answer 20

50:50 mix of each enantiomer, have no effect on plane polarised light

Question 21

What are enantiomers?

Answer 21

mirror images of eachother that cant be superimposed

Question 22

Describe condensation polymerisation to form polyesters

Answer 22

Polyesters are formed form monomers that have carboxylic acid and alcohol functional groups

Ester link (-COO-) formed between monomers

Question 23

Describe condensation polymerisation to form polyamides

Answer 23

Polyamides are formed from monomers that have carboxylic acid and amine functional groups

amide links (-CONH-) formed between monomers

Question 24

Describe the acid and base hydrolysis of the ester groups in polyesters

Answer 24

• Polyesters react slowly in strong aqueous acid to reform the carboxylic acid and alcohol groups of the monomers
• Polyesters react quickly with hot aqueous NaOH to reform the alcohol groups of the monomers and form the salt of the carboxylic acid

Question 25

Describe the acid and base hydrolysis of the amide groups in polyamides

Answer 25

• Polyamides react quickly in strong aqueous acid to form the carboxylic acid groups of the monomers and a diammonium salt
• Polyamides react slowly in hot aqueous NaOH to form the amine groups of the monomers and the salt of the carboxylic acid

Question 26

Can you predict the repeat unit from a given monomer for addition and condensation polymerisation?

Answer 26

maybe

Question 27

Can you predict the monomer(s) required for a given section of a polymer molecule for addition and condensation polymerisation

Answer 27

maybe

Question 28

How are peptides formed?

What is dipeptide and polypepetide?

Answer 28

Amino acids react together to form a peptide in a condensation reaction.

Dipeptide: 2-amino acids
Polypeptide: many amino acids

Question 29

Suggest two benefits of using single stereoisomers in the synthesis of drugs

Answer 29

no/fewer side effects

increases the (pharmacological) activity/effectiveness

Reduces/stops the need for/cost/difficulty in separating
stereoisomers/optical isomers

Question 30

State what is meant by a condensation polymer.

Answer 30

monomers join to form polymer

AND small molecule e.g. H2O/HCl

Question 31

What’s the use of C–C bond formation in synthesis

Answer 31

to increase the length of a carbon chain

Question 32

formation of C-C=/N by reaction of:
(i) haloalkanes with CN– and ethanol, including
nucleophilic substitution mechanism

Answer 32

R-X + CN- –> R-C=/N + Br-