MediumChemistryHigh School (11–12)Organic Chemistry: Some Basic Principles and Techniques › Electronic Effects and Reaction IntermediatesConceptualA-LevelIBJEE Main
Arrange these acids in order of increasing strength: CH₃COOH, Cl₃CCOOH, ClCH₂COOH and Cl₂CHCOOH…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- Arrange these acids in order of increasing strength: , , and .
- Arrange these acids in order of increasing strength: , , and .
Give the reason for each order.
Need a reminder? The key ideaShow
The inductive effect is a permanent pull () or push () of electrons along sigma bonds. It fades with distance. Resonance spreads pi electrons and lone pairs over several atoms. The hybrid is more stable than any one structure, and its equal bonds share the bond order. The electromeric effect is a temporary shift of a pi pair under attack. Hyperconjugation spreads the sigma electrons of an alpha C-H bond, so more alpha hydrogens mean more stability.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
(a) . Each chlorine pulls electrons through the chain by its effect. That weakens the O-H bond and steadies the carboxylate ion. Three chlorine atoms pull the most.
(b) . The effect falls from fluorine to iodine, in the order .
Answer: a stronger effect, or more groups with it, gives a stronger acid.
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