The correct order of increasing acid strength of the compounds:(a) ${\text{CH}}_3{\text{CO}}_2\text{H}$ (b) ${\text{MeOCH}}_2{\text{CO}}_2\text{H}$ (c) ${\text{CF}}_3{\text{CO}}_2\text{H}$ (d) ${\text{Me}}_2{\text{CHCO}}_2\text{H}$ (Isopropyl acetic acid)

Acid strength is increased by electron-withdrawing groups ($-I$ effect) and decreased by electron-donating groups ($+I$ effect).(c) ${\text{CF}}_3{\text{CO}}_2\text{H}$ has three strongly electron-withdrawing Fluorine atoms. It is the strongest.(b) ${\text{MeOCH}}_2{\text{CO}}_2\text{H}$ has an $-\text{OMe}$ group, which is electron-withdrawing ($-I$) relative to alkyl groups. It is stronger than acetic acid.(a) ${\text{CH}}_3{\text{CO}}_2\text{H}$ is the standard.(d) ${\text{Me}}_2{\text{CHCO}}_2\text{H}$ has a larger alkyl group providing a stronger $+I$ effect than a methyl group, making it the weakest.Increasing order: d < a < b < c.