Organic II - AMINES

Question 1

Explain why methylamine is a stronger base than ammonia

Answer 1

lone pair (on N accepts H+
) (1)
CH3 increases electron density (on N)
donates / pushes electrons
has positive inductive effect (1)

Question 2

Suggest a substance that could be added to aq methylamine to produce a basic buffer

Answer 2

CH3NH3Cl or HCl (1)
Or any ammonium compound or strong acid
name or formula

Question 3

Explain the term Bronsted-Lowry base and write an equation for the reaction of methylamine with water to produce an alkaline solution

Answer 3

H+ or proton acceptor (1)
CH3NH2 + H2O EQ ARROW CH3
+NH3 (+) OH–
(1)

Question 4

State and explain the difference in base strength between phenylamine and ammonia

Answer 4

phenylamine weaker (1)
if wrong no marks
lone pair on N (less available) (1)
delocalised into ring (1)

Question 5

Identify a substance that could be added to aq butylamine to produce a basic buffer solution

Answer 5

Any strong acid (but not concentrated)
or any amine salt or ammonium salt of a strong acid

Question 6

Explain why butylamine is a stronger base than ammonia

Answer 6

Lone pair (on N) (in correct context)
1
R group increases electron density / donates electrons /pushes
electrons / has positive inductive effect

Question 7

Explain how the buffer solution is able to resist a change in pH when a small amount of NaOH is added

Answer 7

extra OH–
reacts with
or reaction / equilibrium moves to left
or ratio salt / base remains almost constant (1)