Chap 16: Carboxylic acid and derivatives

Question 1

Why are carboxylic acids more acidic than alcohols?

Answer 1

Electron withdrawing C=O group polarises the O-H bond, weakening it

This also leads to stronger H bonding

Question 2

How to form carboxylic acid from primary alcohols/aldehydes?

Answer 2

KMnO4 or K2Cr2O7, H2SO4 (aq), heat under reflux
Purple KMnO4 decolourises/Orange K2Cr2O7 turns green

Question 3

How to form carboxylic acids from nitriles? (2 ways)

Answer 3

1) HCl or H2SO4 (aq), heat under reflux
2) NaOH (aq), heat under reflux
Followed by acidification using H2SO4 or HCl (aq) at room temp

Question 4

How to form carboxylic acids from alkenes?

Answer 4

KMnO4, H2SO4 (aq), heat under reflux
Purple KMnO4 decolourises (effervescence only if terminal alkene present)

Question 5

How to form benzoic acid from alkyl benzene?

Answer 5

KMnO4, H2SO4 (aq), heat under reflux
Purple KMnO4 decolourises and white ppt of benzoic acid formed

Question 6

How to form carboxylic acid from methyl alcohol or carbonyl?

Answer 6

NaOH (aq), I2 (aq), warm
Followed by HCl or H2SO4 at room temp

Brown I2 decolourised. Yellow ppt of CHI3 formed.

Question 7

How to form esters from carboxylic acid? Why is this way not ideal?

Answer 7

Alcohol, conc. H2SO4, heat under reflux

Reversible reaction that is slow to reach eqm, yield not 100%

Question 8

How to form acyl chloride from carboxylic acid?

Answer 8

PCl3 or PCl5, room temp
SOCl2, room temp
Steamy white fumes of HCl formed