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
