Amines Flashcards
How do you name amines?
- carbon chain then ‘amine’ at the end
e.g 2 carbon chain would be ethanamine
How do you form aliphatic amines from halogenoalkanes & in what conditions ?
Add NH3 to form the salt
Add NH3 to then form amine
Sealed tube, ethanol solvent and excess NH3
Why can’t you add NH3 to a benzene ring to form an amine?
The benzene ring has a high electron density that isn’t susceptible to nucleophilic attack by the ammonia
How can nitrobenzene be reacted to form an aromatic amine?
Add 6 mol of reducing agent
Forms phenylamine and HCl
Needs tin catalyst heated with conc HCl
What is NH3 described as ?
A nucleophile due to lone pair
Acts as a bas (electron donor / H acceptor by forming coordinate bond to H+ ion
Explain the inductive effect
Different functional groups can affect how available a lone pair is by changing electron density
Benzene will draw electron density away from the nitrogen atom, making its lone pair less available
Alkyl groups push electron density towards the nitrogen making it more available
Tertiary amines are the strongest bases
Explain the ethanoylation of primary amides
Nucleophilic addition elimination
methyl amine attacks the carbon and breaks the C=O.
NH2-CH3 adds on and removes 1 hydrogen, oxygen reforms the double bond and Cl is taken away
N-methylethanamide is formed as well as HCL
What is the test for aliphatic and aromatic amines?
Nitric (lll) acid
Describe what happens when HNO2 is added to an amine at room temperature
Forms and alcohol, nitrogen gas and water
The burst of nitrogen gas shows the presence of amine
Can calculate the amount by collecting volume of nitrogen gas
What happens in cold temperatures when HNO2 is added to amines
An intermediate diazonium ion is produced, acting as a bridge to connect another functional group.
Either connecting a phenol or amines
Producing 4-(phenylazo)phenylamine or 4-(phenylazo)phenol
How do azo dyes produce the bright colour
Due to the chromophore ( C=O, C=C) interacting with visible light
What is the same between the reactions with HNO2?
- Both are coupling reaction
- Both involve loss of a small molecule (HCl)
How does colour arise ?
Due to substances absorbing and reflecting light. These wavelengths correspond to a specific colour in which they are observed by the human eye.
