Chapter 27 Flashcards
1
Q
What are amines?
A
- Compounds derived from ammonia, where one or more of the H atoms are replaced by a carbon chain
2
Q
In what 2 ways can amines be classified?
A
- Primary, secondary and tertiary
- Aliphatic or aromatic
3
Q
What are aliphatic and aromatic amines?
A
- In aliphatic amines the N atom is attached to at least one straight or branched carbon chain
- In aromatic amines the N atom is attached to an aromatic ring
4
Q
What are primary, secondary and tertiary amines?
A
- A primary amine is bonded to 1 alkyl or aryl groups
- A secondary amine is bonded to 2
- A tertiary amine is bonded to 3
5
Q
How are primary amines named? Give examples.
A
- If the amine is at the end of the chain, you add the suffix -amine (e.g. ethylamine)
- If the amine is not on carbon 1, you use the prefix amino- (e.g. 2-aminobutane)
6
Q
How are secondary and tertiary amines named?
A
- If they’re attached to multiples of the same alkyl chain, you use the prefix di- or tri- (e.g. dimethylamine)
- If they’re attached to different alkyl chains, use the short one as a prefix (if there are 2 other chains, put them in alphabetical order) and add an N to show that the other chain is also bonded to the nitrogen atom (e.g. N-methylpropylamine, N-ethyl-N-methylpropylamine, N,N-dimethylethylamine)
7
Q
What can amines can act as in chemical reactions?
A
- Weak bases, as the lone pair on the N atom can accept a proton and form a dative covalent bond
- Nucleophiles, as there is a lone pair of electrons on the N atom
8
Q
How do amines react with acids? Give an example.
A
- They form an ammonium salt
- Hydrochloric acid + propylamine -> propylammonium chloride
9
Q
How can primary amines be prepared?
A
- Salt formation: reacting a haloalkane with ammonia to form an ammonium salt
- Amine formation: reacting the ammonium salt with sodium hydroxide to form the primary amine
10
Q
How are secondary and tertiary amines formed?
A
- To form secondary amines, the process to form primary amines repeats, but with a primary amine taking the role of ammonia (the N still has a lone pair)
- To form tertiary amines, secondary amines are reacted with a haloalkane
11
Q
Give the equations for the formation of propylamine. Give the conditions, and mechanism if applicable.
A
- Step 1: nucleophilic substitution
- Excess ethanolic ammonia
- 1-chloropropane + ammonia -> propylammonium chloride
- Step 2: check mechanism
- propylammonium chloride + sodium hydroxide -> amine + sodium chloride + water
12
Q
Why is excess ethanolic ammonia used in the formation of primary amines?
A
- Ethanol is used as a solvent instead of water, as otherwise the haloalkane would react with water via nucleophilic substitution to form an alcohol
- Excess ammonia is used to reduce (although it’s not possible to entirely avoid) further substitution of the amine to form secondary and tertiary amines
13
Q
How are aromatic amines prepared?
A
- Nitrobenzene is reduced using tin and concentrated hydrochloric acid
14
Q
Give the reaction and conditions for the formation of phenylamine.
A
- Nitrobenzene + 6[H] -> phenylamine + 2H2O
- Conditions: Sn and concentrated HCl
15
Q
What are amino acids?
A
- Compounds with an amine group on one end, and a carboxyl group on the other
16
Q
What are α-amino acids, and how do they differ?
A
- They only have one central carbon atom which has a H group, and an R group
- The R group is what differs between them
17
Q
How do amino acids react with acids?
A
- The amine group reacts to form an ammonium salt (NH3+X)
18
Q
How do amino acids react with aqueous alkalis?
A
- The carboxyl group reacts to form a carboxylate salt and water
19
Q
How do amino acids react with alcohols?
A
- If an amino acid is heated under reflux with an acid catalyst, it forms an ester and water
- The amine group is also protonated due to the acidic conditions
20
Q
What is optical isomerism?
A
- A type of stereoisomerism
21
Q
What are optical isomers? What is a pair of optical isomers called?
A
- Stereoisomers that are non-superimposable mirror images of each other (think hands)
- (Superimposable: can perfectly overlap if they were in the same place)
- The pair are called enantiomers
22
Q
What causes optical isomerism?
A
- One or more chiral centres in a molecule
23
Q
What are chiral centres?
A
- Chiral centres are usually carbon atoms that are bonded to 4 other groups; this makes them asymmetric (if it was bonded to less than 4 groups, or 2 or more of the same group, you can split the molecule in half and it would look the same)
24
Q
How is the number of chiral centres linked to the number of enantiomers?
A
- Number of enantiomers: 2^n
- n: number of chiral centres
25
What is condensation polymerisation?
- The joining of monomers with the loss of a small molecule
26
Give 2 examples of types of polymers formed through condensation polymerisation.
- Polyesters
- Polyamides
27
What is required for condensation polymerisation to take place?
- 2 different functional groups
28
What are the 2 ways of making polyesters? What small molecule is made in each reaction, and how much is formed?
- Making them from one monomer that has both a hydroxyl and a carboxyl group
- n-1 water molecules are formed
- Making them from 2 different monomers where one is a dicarboxylic acid and the other is a diol
- 2n-1 water molecules are formed
29
How else can polyesters be formed? What difference is there in the reaction?
- Using acyl and diacyl chlorides instead of carboxylic and dicarboxylic acids
- HCl is formed instead of water
30
What are the 4 ways of making polyamides? What small molecule is made in each reaction, and how much is formed?
- Making them from one monomer that has both an amine and a carboxyl group
- n-1 water molecules are formed
- Making them from one monomer that has both an amine and an acyl chloride group
- n-1 HCl molecules are formed
- Making them from 2 different monomers where one is a dicarboxylic acid and the other is a diamine
- 2n-1 water molecules are formed
- Making them from 2 different monomers where one is a diacyl chloride and the other is a diamine
- 2n-1 HCl molecules are formed
31
What are the 2 main differences between addition and condensation polymerisation?
- Addition polymerisation uses a monomer with a C=C, while condensation polymerisation uses either one monomer with 2 functional groups, or 2 monomers where each has 2 of the same functional group
- In addition polymers, there is a constant carbon chain, while in condensation polymers there are ester and amide linkages
32
In what way do polyesters behave in the same way as esters?
- They can both be hydrolysed by aqueous acid or alkali
33
What does the hydrolysis of polyesters by acid produce?
- Carboxylic acid and alcohol
34
What does the hydrolysis of polyesters by aqueous alkali produce?
- Carboxylate salt and alcohol
35
What does the hydrolysis of polyamides by acid produce? What do you need to remember to include?
- Alkylammonium ion and carboxylic acid
- Any nitrogen atoms are protonated
36
What does the hydrolysis of polyamides by aqueous alkali produce?
- Carboxylate salt and amine
37
Why are some polyesters biodegradable?
- They can be hydrolysed
