2020 P1 Q24 - Comparing Basicity of Amines

Let's take a look at 2020 A Levels H2 Chemistry Paper 1 Question 24.

2020 p1 q24 question

We need to compare and explain the equilibrium positions of the acid base reaction between ethylamine and diethylamine with HCl.

Let us start by comparing the basicity of ethylamine and diethylamine.

The basicity of nitrogen compounds is determined by the availability of lone pair on nitrogen.

The more available the lone pair on nitrogen, the stronger the lewis base.

2020 p1 q24 comparing basicity ethylamine vs diethylamine

Ethylamine has only 1 electron donating alkyl group.

This makes the lone pair on nitrogen less available for donation.

Hence ethylamine should be a weaker base.

Diethylamine has 2 electron donating alkyl groups, which makes the lone pair on its nitrogen more available.

This means diethylamine is a stronger base than ethylamine.

In general the more substituted the amine, the stronger the base:

tertiary amine > secondary amine > primary amine > ammonia

Therefore we will expect the position of equilibrium for the second equilibrium to lie further to the right.

2020 p1 q24 deduce POE

Finally we can compare the options and determine the answer to this question is option D.

2020 p1 q24 answer

Topic: Nitrogen Compounds, Organic Chemistry, A Level Chemistry, Singapore

Back to list of questions for 2020 A Level H2 Chemistry Paper 1.

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