Why is benzoic acid more soluble in alkaline solution rather than neutral or acid solution?

Answer 1

It would depend on the solvent that phenol or benzoic acid are being placed in. Benzoic acid would be more soluble in a polar solvent because of the carbonyl group's extreme electronegativity.

Answer 2

If you are referring to a phenoxide ion when you say "phenol ion." I can help you. It all has to do with the delocalisation of the negative charge. To be clear, in the phenoxide ion, oxygen is the center of highest electron density. Because oxygen has a lone pair of electrons that can transfer to the nearest carbon, phenoxide ion can must be described by resonance. Subsequently, the delocalisation of the electrons makes the phenoxide ion than stable.

Answer 3

The reason why phenol is more soluble in NaOH than in water is because phenol is slightly acidic. The Ka for phenol in water is 1e-10. Of course, this is not very strong. But by mixing with NaOH, it causes the phenol to release the H+ to form sodium phenoxide. The one negative charge on this compound can move to different locations in the phenol to form different resonances (4 resonances in total) and create verystable compound. Furthermore, the reaction between NaOH and phenol is exothermic, and the equilibrium lies far to the right. This makes the sodium phenoxide extra stable.

Phenol has a very weakly acidic hydrogen (pka 1e-10), but mixing with NaOH will cause an acid base reaction:

Ph-OH + Na+OH- ----> Ph-O-Na+ + H2O

The above reaction produces a salt, sodium phenoxide, NaOPh. Like sodium chloride (NaCl), NaOPh is soluble.

Mixing PhOH + H2O does not give a salt because water is not a strong enough base to deprotonate phenol. Hence due to the amount of carbons (C6H6O is formula for PhOH), this compound is not expected to be water soluble. Too many carbons. Note also that inspite of the polar -OH group, this molecule is still not soluble because the -OH group is small in comparison to the rest of the molecule.

Answer 4

Benzoic Acid is more Acidic than Phenol due to resonance effect.

Answer 5

because it is an acid which forms a salt with alkali and such salts are soluble in water.

Answer 6

Because phenols have a lone pair of electron on the oxygen atom and this is drawn into the benzene ring thereby increasing the electron density of the ring which attracts more electrophiles.