Some Organic Chemistry Problems-solve
The study of organic chemistry can either be fascinating subject as the beginning of a journey to greater understanding or as if often the case a means to some end. The truth is organic chemistry is not like general chemistry, it is the gateway and linch pin for other chemical and life science courses a student may study.
Studying organic chemistry should include
- Knowing and using all available study resources
- Creating an effective study environment and
- Implementing study sessions using a review, read and practice, preview methodology
- Solving problems using a systematic approach
Solved Examples
Question 1: 2,4,6-Trinitrotoluene is a relatively acidic compound. Explain why the proton is easily removed from the methyl group?
Solution:The proton is removed easily because the anion formed after the removal of the proton is stabilized by resonance with the three -NO2 groups as shown below.

Question 2: Predict the relative acidity of the following pairs-(i)H3O+ and NH4+
(ii)CH3NH2 and CH3OH
Solution 2: We examine the conjugate base being formed when each acid loses a proton; the better the conjugate base accommodates the electron pair left behind, the weaker the base and hence stronger the acid.
H3O+ > NH4+
Oxygen is more electronegative than nitrogen and can hold on to electrons better. Therefore H3O+ will tend to lose the proton more rapidly and more acidic.
CH3OH > CH2NH2
Again because oxygen is more electronegative than nitrogen CH3OH is more acidic.
Question 3: The 'Ka' of acetic acid is 1.2x10-5 and the pKa of phenyl acetic acid is 4.31.
CH3COOH C6H5CH2COOH
Ka = 1.2x10-5 pKa = 4.31
Calculate the pKa of acetic acid and Ka of phenyl acetic acid. Which of the two acids is stronger? Explain.
Solution 3:CH3COOH & C6H5CH2COOH
Ka of CH3COOH = 1.2 x 10-5 pKa = 4.31
pKa = -log Ka
Substitute the values to obtain pKa and Ka
pKa = 4.76 Ka = 5.1 x 10-5
Phenylacetic acid is stronger because of the inductive electron withdrawing effect of the phenyl group.
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