Amines Flashcards
How do you amines ?
-amine
Or
Amino-
Why are amines so reactive ?
The lone pair of electrons on the nitrogen - due to the polar N-H bond
What shape are amines around the N and what is the bond angle ?
Trigonometry pyramidal, 107º due to lone pain on N
What kind of intermolecular forces do they have and why ?
Hydrogen bonding due to the polar N-H bond and lone pair of electrons on the N atom
How are amines produced ?
- when one or more of the hydrogen atoms in ammonia is replaced by another group
- can be primary, secondary or tertiary
What mechanism is involved in the production of amines ? And what is the product?
Amines are produced from the reaction of a halogenoalkanes with ammonia
- nucleophilic substitution
- produces a primary amine and ammonium salt
What are primary amines ?
- have a general formula of RNH2
- R can be an alkyl or aryl group
- amines are named using the suffix -amine, for example methyl amine
What are secondary amines ?
- have the general formula RR’NH.
What are tertiary amines ?
- general formula - RR’R’‘N
- eg trimethlyamine
- different R groups are put in alphabetical order
Do amines have intermolecular forces which are stronger than or weaker than alcohols?
- weaker, as N has lower electronegativity than O therefore has weaker hydrogen bonding
What state are amines at 298K ?
Short chains are gases, longer chains are volatile liquids
What do amines smell like and why ?
- fishy rotten meat
- releases di and triamines
Which primary amines are soluble in water/alcohols ?
- up to 4 carbon atoms, as they can hydrogen bond to water molecules
- after this the non-polarity of hydrocarbons chain makes them insoluble
Is phenylamine soluble ?
- no not very soluble, due to the non-polarity of the benzene ring
When can amines act as bases ?
When they bond with H+ ion
When do amines act as nucleophiles ?
When they bond with an electron-deficient C atom
What is the product from the basic action of an amine with water ?
An ammonium ion, which forms a salt with an anion
Is the product soluble in water ?
Yes, as it is so attracted to the polar bonds in H2O
How could you regenerate the soluble amine from the ammonium salt ?
Add a strong base (NaOH), which removes H+ ions from ammonium ions
What makes a base the strongest ?
-greatest electron density around the N atom, making it a better electron pair donor
What is a positive inductive effect ?
Donating electrons increase density around N
What is a negative inductive effect ?
Negative means remove electrons , decrease density around N
Why are tertiary amines never good bases ?
They are insoluble in water
How would you maximise the yield of the primary amine ?
Use excess ammonia
How do you get from a nitrile to a primary amine ?
Reduction using nickel / hydrogen catalyst
Why is this a purer method of synthesising amines ?
Because it only produces the primary amine
What conditions are needed to form nitrobenzene from benzene ?
Concentrated H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack
What are cationic surfactants ?
These molecules are complexes with a positive and negative end. This makes them good conditioners as the two ends are attracted to different substances, preventing static from building up on surfaces. Cationic surfactants are therefore useful in industry.
Can amines undergo Nucleophilic Addition-Elimination reactions ?
Amines can also undergo nucleophilic addition-elimination reactions with acyl chlorides to produce amides and N-substituted amides.
- This same reaction mechanism can also occur with acid anhydrides to produce an amide and a carboxylic acid.
