Tca has greater acidity than acetic acid. Bcos of EAIE of 3 cl increases the positivity of carbonyl C making release of proton easier. Please explain. Why Cl increases positivity when Cl is infact an electronegative element
Since Cl is so electronegativity, it is an electron withdrawing agent. That means it is pulling, through the inductive effect, electrons from elsewhere which makes the the carbonyl more positive and that helps release the proton.
While it may seem counterintuitive, in the case of the compound trichloroacetic acid (TCA), the presence of three chlorine atoms increases the positive charge on the carbonyl carbon and enhances its acidity compared to acetic acid. This effect can be explained by considering the electron-withdrawing nature of chlorine atoms.
To understand this concept, let's break it down step by step:
1. Electron-Withdrawing Nature of Chlorine: Chlorine is indeed an electronegative element, meaning it attracts electrons towards itself in a chemical bond. In TCA, each chlorine atom pulls electron density away from the carbonyl carbon, creating a partial positive charge on the carbon atom.
2. Effect of Electron-Withdrawing Groups on Stability: The positive charge on the carbonyl carbon in TCA destabilizes the molecule, making it highly reactive. Due to this instability, TCA tends to readily lose a proton (H+) and donate it as an acid.
3. Enolization and Resonance: When TCA loses a proton, it forms an enolate ion, which involves the transfer of a hydrogen atom from the acidic carbon to the oxygen. This process is assisted by the resonance stabilization of the enolate ion, which spreads the positive charge over the oxygen and adjacent carbon atoms.
4. Increased Acidity: The presence of the three chlorine atoms in TCA increases the electron-withdrawing effect and, consequently, the partial positive charge on the carbonyl carbon. This strengthens the positive charge and enhances the acidity of TCA, making it a stronger acid compared to acetic acid.
In summary, although chlorine is electronegative, its presence in trichloroacetic acid increases the positive charge on the carbonyl carbon, making it more acidic than acetic acid. This is due to the electron-withdrawing nature of chlorine, which destabilizes TCA and facilitates the release of a proton.