Final answer:
The acid strength increases as we move from CH3 to CCl3 due to higher electronegativity and stronger inductive effects of the chlorine atoms.
Step-by-step explanation:
Two factors that affect the strength of the acid as the group R changes from CH3 to CCl3 are electronegativity and inductive effects.
Electronegativity: As the group changes from CH3 to CCl3, the atoms bonded to the central carbon are more electronegative.
Chlorine has a higher electronegativity compared to hydrogen, which means it can pull the electron density towards itself more effectively.
This increases the polarization of the bond between the acidic hydrogen and the molecule, thereby increasing acidity.
Inductive effects: Chlorine atoms also exert a stronger inductive effect than hydrogen due to their higher electronegativity.
The inductive effect refers to the shifting of electron density through sigma bonds in a molecule. In the case of CCl3, the electron-withdrawing effect of the three chlorine atoms makes the molecule a stronger acid compared to CH3 because it stabilizes the negative charge on the conjugate base, enhancing the acid's ability to donate a proton.