AMINES, AMINO ACIDS AND PROTEINS

Question 1

What are the two main categories amines can be classified into?

Answer 1

aliphatic and aromatic, aliphatic amines have alkyl groups attached to the nitrogen atom, while aromatic amines contain a nitrogen atom directly bonded to a benzene ring.

Question 2

What are primary amines?

Answer 2

One hydrogen on an ammonia is replaced and the general formula is RNH2

Question 3

What are secondary amines?

Answer 3

Two hydrogens on an ammonia are replaced and the general formula is R2NH

Question 4

What are tertiary amines?

Answer 4

Three hydrogens on an ammonia are replaced and the general formula is R3N

Question 5

What does does the nitrogen atom in amines possess?

Answer 5

A lone pair of electron. The lone pair results in a trigonal pyramidal geometry with a bond angle slightly less than 109.5. Also makes amines nucleophilic.

Question 6

Why do amines act as weak Bronsted-Lowry bases?

Answer 6

due to their ability to accept protons using the lone pair. amines react with acids by accepting H+ ions to form ammonium salts

Question 7

How to form primary amines

Answer 7

Primary aliphatic amines can be produced by heating a halogenoalkane with excess ethanolic ammonia

Question 8

How to form secondary amines

Answer 8

Secondary aliphatic amines can be produced by reacting a halogenoalkane with a primary amine.

Question 9

How to form tertiary amines

Answer 9

Tertiary aliphatic amines can be produced by reacting a halogenoalkane with a secondary amine.

Question 10

Mechanism of amine formation

Answer 10

nucleophilic substitution mechanism involves two steps:
1. The nucleophile (ammonia or amine) attacks the halogenoalkane, displacing the halogen and forming an alkylammonium salt.
2. The alkylammonium salt is the deprotonated by a base (e.g. the nucleophile or a separate base) to form the amine product.

Question 11

Aromatic amines are produced by reducing nitro compounds in a two-step process:

Answer 11

1. The nitro compound is heated under reflux with tin and concentrate HCl to form an ammonium salt.
2. The ammonium salt is then treated with aqueous NaOH to give the free amine

Question 12

What are aromatic amines useful for in organic synthesis?

Answer 12

making pharmaceuticals, dyes, and other compounds

Question 13

What two functional groups are amino acids made up of?

Answer 13

• An amino group (-NH2)
  -A carboxyl group (-COOH) (acid group)

Question 14

How are amino acids named?

Answer 14

1. Common names, e.g. glycine and alanine.
2. Systematic IUPAC names, which are based on the carbon backbone.

Question 15

What are the steps to name an amino acid systematically?

Answer 15

1. Identify the longest carbon chain that includes the carboxyl carbon
2. Start numbering the carbons from the carboxyl carbon, assigning it the number 1
3. Specify the position and identify of the amine substituent

Question 16

Amino acid reaction with alkalis

Answer 16

The carboxyl group can react with aqueous alkalis such as NaOH (aq) to form carboxylate salts and water

Question 17

Amino acid reaction with acids

Answer 17

The amine group can react with acids like HCl to form ammonium salts

Question 18

Esterification of amino acids

Answer 18

The carboxyl group is capable of reacting with alcohols to form esters and water, in a reaction catalysed by concentrated H2SO4

Question 19

What are amides?

Answer 19

Amides are organic compounds that contain the functional group -CONH2. They are derived from carboxylic acids by replacing the hydroxyl group with an amino group

Question 20

What are primary amides?

Answer 20

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O) and two hydrogen atoms.

Question 21

What are secondary amides?

Answer 21

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O), one hydrogen and one alkyl or aryl group.

Question 22

What are tertiary amides?

Answer 22

These are amides where the nitrogen atom is bonded to one carbonyl group (C=O) and two alkyl or aryl groups.

Question 23

How can amides by synthesized through a reaction with ammonia?

Answer 23

The reaction between acyl chlorides and ammonia produces primary amides.

Question 24

How can amides by synthesized through a reaction with amines?

Answer 24

The reaction between acyl chlorides and primary amines produces secondary amides, also known as N-substituted amides.

Question 25

In reactions where amides are made from acyl chlorides what typically happens to the HCl produced?

Answer 25

It reacts with any excess ammonia or amine to form ammonium salts.

Question 26

What is optical isomerism?

Answer 26

A type of stereoisomerism where isomers have the same structural formula but different arrangements of atoms in space.

Question 27

What is a chiral carbon?

Answer 27

A carbon with four different groups attached to it.

Question 28

How do you identify and draw optical isomers?

Answer 28

1. Identify the chiral carbon - carefully draw all hydrogen atoms to clearly identify each attachment. Look for the carbon atom connected to four different groups. 2. Sketch the optical isomers - illustrate one isomer with its groups arranged tetrahedrally around the chiral carbon. Next draw its mirror image.

Question 29

What are condensation reactions?

Answer 29

Condensation polymerization reactions lead to the formation of long polymer chains through the joining of monomers, accompanied by the elimination of small molecules like water (H2O) or hydrogen chloride (HCl)

Question 30

What are the key features of condensation polymers?

Answer 30

- They are formed from reactions between monomers that contain at least two functional groups. - The functional groups on each monomer react, forming links between repeat units. - A small molecule, such as water or hydrogen chloride, is eliminated each time a link forms.

Question 31

Common types of condensation polymers are:

Answer 31

- Polyesters -Polyamides

Question 32

What are polyesters?

Answer 32

A type of condensation polymer formed from the reaction between dicarboxylic acids (or derivatives such as acyl chloride) and diols. The carboxyl (-COOH) and hydroxyl (-OH) groups react, forming ester links in the polymer chain.

Question 33

What are polyamides?

Answer 33

Polyamides are another type of condensation polymer, formed from dicarboxylic acids (or derivatives such as acyl chlorides) and diamines. The carboxyl and amine groups react, forming amide links within the polymer chain.

Question 34

How can condensation polymerisation be reversed?

Answer 34

Through hydrolysis, which involves adding water across the links. However, hydrolysis with just water is very slow, so acids or bases are typically used to speed up the reaction.

Question 35

Conditions that more rapidly hydrolyse polyamides and polyesters

Answer 35

polyamides are hydrolysed more rapidly under acidic conditions. polyesters are hydrolysed more rapidly under basic conditions

Question 36

How are polyamides hydrolysed?

Answer 36

The acid protonates the carbonyl group, enabling water to attack and split the amide linkage, thereby reforming the dicarboxylic acid and the ammonium salt of the diamine

Question 37

How are polyesters hydrolysed?

Answer 37

The hydroxide ion attacks the carbonyl carbon, breaking the ester linkage and reforming thr diol and the dicarboxylic salt.

Question 38

How to deduce the monomers that form a condensation polymer?

Answer 38

1. Identify the amide (HN-CO) or ester (CO-O) linkage between repeating units 2. Cut the link in the middle to separate the polymer chain. 3. Add an H atom or -OH group to both ends of the molecules. H atoms are added to N or O atoms, and -OH groups to C atoms.

Question 39

How to draw repeat unit from condensation monomer?

Answer 39

1. Place the structures of the two monomers side by side. 2. Remove an H atom from one monomer (e.g. diol or diamine) and an OH group from the other (e.g. dicarboxylic acid), forming an H2O molecule as a by-product. For diacyl chlorides, remove Cl instead of OH, forming HCl 3. Connect the monomers through either an amide or ester linkage, depending on their functional groups. 4. To indicate continuity in the polymer chain, remove another H atom and OH/Cl group from the opposite ends.

Question 40

Compare addition and condensation polymerisation

Answer 40

1. Addition uses alkenes as monomers, condensation uses carboxylic acids, acyl chlorides, amines, alcohols, amino acids monomers 2. The polymer chain of addition polymerisation is a continuous chain of carbon atoms and condensation polymerisation contains ester or amine bonds 3. In addition polymerisation the only product formed is the polymer whereas condensation polymerisation forms the polymer and small molecule.