Compare acidic strength of following :-(I) CF3COOH         (II) CF3CH2COOH(III) NO2–CH2COOHA I > II > III B I > III > II C III > I > II D III > II > I

To compare the acidic strength of the given compounds, we need to consider the factors that influence acidity.

1. Inductive Effect: The presence of electron-withdrawing groups increases the acidity of a compound. In this case, compound (III) NO2–CH2COOH has a nitro group (-NO2) attached to the carbon chain, which is a strong electron-withdrawing group. This makes compound (III) the most acidic among the given compounds.

2. Resonance Effect: The presence of resonance structures can stabilize the conjugate base, making the compound more acidic. However, none of the given compounds have any resonance structures.

3. Electron Density: The more electronegative atoms are attached to the acidic hydrogen, the more acidic the compound becomes. In this case, both compounds (I) CF3COOH and (II) CF3CH2COOH have a trifluoromethyl group (-CF3) attached to the acidic hydrogen. Since both compounds have the same electron-withdrawing group, we need to consider the effect of the alkyl chain. The longer the alkyl chain, the more electron-donating it is, which decreases the acidity. Therefore, compound (II) CF3CH2COOH is less acidic than compound (I) CF3COOH.

Based on these factors, the correct order of acidic strength is: III > I > II

Therefore, the correct answer is option C: III > I > II.