Question

Which of the following solvents has maximum distribution coefficient at 200°C for the extraction of acetic acid from acetic acid – water system?

• A. butanol
• B. ethyl acetate
• C. toluene
• D. hexane

Hint:

When selecting solvents for extraction, the distribution coefficient is a key factor. Solvents with higher coefficients are generally more effective in extracting solutes.

Answer 1

The Correct Option is B

Step 1: Understanding the distribution coefficient.
The distribution coefficient (or partition coefficient) of a solvent is a measure of its relative ability to extract a solute from one phase (usually water) into another phase (such as an organic solvent). The higher the distribution coefficient, the more effective the solvent is for extraction. For acetic acid extraction, the distribution coefficient is typically higher for solvents like ethyl acetate compared to others.
Step 2: Conclusion.
Ethyl acetate is known to have the maximum distribution coefficient at 200°C for the extraction of acetic acid from an acetic acid-water system. Therefore, the correct answer is (2).

Answer 2

Choosing the best solvent for extracting acetic acid from water comes down to how strongly the solvent can interact with and dissolve acetic acid while remaining reasonably immiscible with water. Let's compare the listed solvents on this basis.

1. Butanol: Butanol is a reasonably good extractant for acetic acid because of its hydroxyl group, but it is also partly miscible with water, which reduces the sharpness of the phase split and its practical distribution advantage compared to a solvent like ethyl acetate.
2. Ethyl acetate: Ethyl acetate has an ester functional group that can hydrogen-bond effectively with acetic acid's carboxylic acid group while remaining largely immiscible with water, giving it the highest distribution coefficient for acetic acid among the options listed at this temperature.
3. Toluene: Toluene is a nonpolar aromatic hydrocarbon with essentially no capacity to hydrogen-bond with acetic acid, so acetic acid strongly prefers to stay in the aqueous phase, giving toluene a low distribution coefficient.
4. Hexane: Hexane is an even more nonpolar solvent than toluene, with no functional groups to interact favorably with the polar carboxylic acid group of acetic acid, giving it the lowest distribution coefficient of the four.

Among these solvents, ethyl acetate offers the best combination of favorable interaction with acetic acid and limited water miscibility, giving it the maximum distribution coefficient.

Therefore, the correct answer is ethyl acetate.