O- Amines

Question 1

shape + bond angle of amines

Answer 1

pyramidal
107

Question 2

bonding

Answer 2

H bonds w. NH2 groups
- x as strong as those in alcohols ∵ N ↓ electronegative than O

Question 3

state of matter at room temp

Answer 3

• shorter chain amines (methyl + ethyl)- gases
• longer chain- volatile liquids

Question 4

solubility

Answer 4

• primary amines w/ chain lengths up to 4 C- v soluble in H2O + alcohols ∵ form H bonds w/ the solvents
• phenylamine x soluble in H2O- ∵ benzene ring x form H bonds

Question 5

reactivity

Answer 5

lone pair forms bond with:
1. as a base –> H+ ion
2. as a nucleophile –> δ+ C

both a Bronsted-Lowry base (proton acceptor) + Lewis base (lone pair donor)

Question 6

Why does phenylamine dissolve in excess hydrochloric acid despite being relatively insoluble?
What then happens if a strong base (eg. NaOH) is added?

Answer 6

• forms a soluble ionic salt
• base removes proton from salt –> regenerates insoluble amine

Question 7

rank base strengths for primary, secondary alkylamines, and arylamines

Answer 7

secondary > primary > arylamines
- aryl groups withdraw e- from N
- ∵ lone pair overlaps w/ delocalised system on benzene ring
- N- weaker e- pair donor

Question 8

compare base strengths for a primary alkylamine and ammonia

Answer 8

• inductive effect in alkylamine (alkyl group pushing e- towards N)
• ↑ e- density on N
• N –> better e- pair donor

Question 9

compare base strengths of primary and secondary alkylamines

Answer 9

secondary > primary
- 2 inductive effects

Question 10

compare base strengths for secondary and tertiary alkylamines

Answer 10

seondary > tertiary
- tertiary ↓ soluble in water