Amines

Question 1

What is the strength of a base dependant on?

Answer 1

The availability of the lone pair of electrons on the nitrogen. The higher the electron density, the more readily available the electrons are

Question 1

Why do aromatic amines have he weakest base strength?

Answer 1

Benzene is an electron withdrawing group so it pulls electrons away from the nitrogen into the ring
-The electron density at nitrogen reduces so lone pair availability is reduces so aromatic amines are less basic.

Question 2

Why do aliphatic amines have the strongest base strength?

Answer 2

Alkyl groups are electron pushing groups so they push the electrons towards nitrogen. The electron density at nitrogen increases so he lone pair availability is increased
-so primary aliphatic mines are more basic.

Question 3

Downside of using nucleophillic substitution to produce amines

Answer 3

produces primary, secondary, tertiary and quaternary salts so its products are impure
-the amines still have a lone pair of electrons on the nitrogen so act as a nucleophile and react with the halogenoalkanes

Question 4

What is needed to reduce nitriles to amines

Answer 4

-nickel catalyst
-hydrogen gas

Question 5

What is the overall reaction for reducing nitriles to amines?

Answer 5

r-CH2-CN + 2H2 / 4[H] <> R-CH2-CH2NH2

Question 6

Butylamine can also be prepared in a two-step synthesis starting from
1-bromopropane, CH3CH2CH2Br. Write an equation for each of the two steps in this
synthesis.

Answer 6

-CH3CH2CH2Br + KCN → CH3CH2CH2CN + KBr
-CH3CH2CH2CN + 2H2 → CH3CH2CH2CH2NH2

Question 7

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

Answer 7

-HCl

Question 8

Write an equation for the reaction
of methylamine with water to produce an alkaline solution.

Answer 8

CH3NH2 + H2O ( ) CH3
+NH3 (+) OH–

Question 9

Explain how the buffer solution in part (a)(ii) is able to resist a change in pH
when a small amount of sodium hydroxide is added.

Answer 9

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

Question 10

Equation for formation of electrophile in adding NO2 to benzene with acyl chloride

Answer 10

HNO3 + 2H2SO4 → NO2 + H3O+
+ 2HSO4

Question 11

Reagents used in addition of NO2 to benzene

Answer 11

-conc HNO3
-conc H2SO4