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Why is benzoic acid more soluble in an aqueous alkaline solution than neutral or acid solution?
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Khaled Ahmed
Why is benzoic acid more soluble in an aqueous alkaline solution than neutral or acid solution?
Always remember in case of benzoic acids derivatives
Any group present at ortho position increases the acidity of benzoic acid, irrespective of its nature.
This is due to the ortho effect. When a group is present at ortho position steric factors comes into picture due to which the carboxylic acid group tends to go out of the plane of benzene due to which it's resonance stabilization is inhibited.
Always remember in case of benzoic acids derivatives
Any group present at ortho position increases the acidity of benzoic acid, irrespective of its nature.
This is due to the ortho effect. When a group is present at ortho position steric factors comes into picture due to which the carboxylic acid group tends to go out of the plane of benzene due to which it's resonance stabilization is inhibited.
Benzoic Acid partially ionises as benzoate ion and Hydrogen ion as given below.
C6H5-COOH ———->> C6H5-COO- +H+
In alkaline medium the above equilibrium shifts toward the right and the ionisation of Benzoic Acid increases. The H+ ion formed is neutralised by the OH- ion present in the Alkaline solution and thus making it more SOLUBLE.
On the contrast in acidic medium the equilibrium shifts towards the left ,thus reducing the ionisation of Benzoic Acid. So either in Acidic or neutral medium It is less soluble.
Benzoic Acid partially ionises as benzoate ion and Hydrogen ion as given below.
C6H5-COOH ———->> C6H5-COO- +H+
In alkaline medium the above equilibrium shifts toward the right and the ionisation of Benzoic Acid increases. The H+ ion formed is neutralised by the OH- ion present in the Alkaline solution and thus making it more SOLUBLE.
On the contrast in acidic medium the equilibrium shifts towards the left ,thus reducing the ionisation of Benzoic Acid. So either in Acidic or neutral medium It is less soluble.
In benzoic acid phenyl group act as a electron donating group which causes -I effect in benzoic acid due to which electron density on Oxygen atom of carboxylic acid group is increased and hence removal of Acidic Hydrogen becomes difficult. That is why benzoic acid is less acidic.
On the other hand formic acid has no such type of group which can donate electron or withdraw electron so removal of Acidic Hydrogen from formic acid becomes easy as compared to benzoic acid so it is more acidic then benzoic acid.
Plz upvote and comment if you found this answer helpful.
In benzoic acid phenyl group act as a electron donating group which causes -I effect in benzoic acid due to which electron density on Oxygen atom of carboxylic acid group is increased and hence removal of Acidic Hydrogen becomes difficult. That is why benzoic acid is less acidic.
On the other hand formic acid has no such type of group which can donate electron or withdraw electron so removal of Acidic Hydrogen from formic acid becomes easy as compared to benzoic acid so it is more acidic then benzoic acid.
Plz upvote and comment if you found this answer helpful.
Benzoic acid is first and foremost a weak acid and thus dissociates partially in water:
C6H5COOH + H2O <---> C6H5COO- + H3O+
From this equation and the structure of benzoic acid, you can tell three things:
In a neutral solution, benzoic acid is slightly soluble in water. It is nearly insoluble in cold water but highly soluble in hot water.
This is because even though water can form hydrogen bonds with the carboxylate functional group, the bulk of the benzoic acid is still the large benzene ring, which can only form Van der Waals forces of attraction with water (significantly weaker than hydrogen bonding). Also, even though benzoic acid can dissociate in water, as it is a weak acid, it can only dissociate partially, which is insufficient to dissolve benzoic acid. Thus, benzoic acid is insoluble in cold water.
However, as temperature increases, more energy is present to overcome the hydrogen bonding between water molecules to form weaker Van der Waals forces of attraction between benzoic acid and water. Also, more energy is present to drive the dissociation of benzoic acid forward, as it is endothermic, thus benzoic acid becomes more soluble in hot water.
In alkaline medium, benzoic acid becomes soluble. The abundant OH- ions will react fully with benzoic acid in acid-base reaction to form water and benzoate ion, which now is soluble in water due to strong ion-dipole forces of attraction.
In acidic medium, benzoic acid becomes insoluble. The increase in concentration of H+ ions will shift the position of equilibrium of dissociation of benzoic acid to the left, causing benzoic acid to be hardly soluble in acidic medium.
Benzoic acid is first and foremost a weak acid and thus dissociates partially in water:
C6H5COOH + H2O <---> C6H5COO- + H3O+
From this equation and the structure of benzoic acid, you can tell three things:
In a neutral solution, benzoic acid is slightly soluble in water. It is nearly insoluble in cold water but highly soluble in hot water.
This is because even though water can form hydrogen bonds with the carboxylate functional group, the bulk of the benzoic acid is still the large benzene ring, which can only form Van der Waals forces of attraction with water (significantly weaker than hydrogen bonding). Also, even though benzoic acid can dissociate in water, as it is a weak acid, it can only dissociate partially, which is insufficient to dissolve benzoic acid. Thus, benzoic acid is insoluble in cold water.
However, as temperature increases, more energy is present to overcome the hydrogen bonding between water molecules to form weaker Van der Waals forces of attraction between benzoic acid and water. Also, more energy is present to drive the dissociation of benzoic acid forward, as it is endothermic, thus benzoic acid becomes more soluble in hot water.
In alkaline medium, benzoic acid becomes soluble. The abundant OH- ions will react fully with benzoic acid in acid-base reaction to form water and benzoate ion, which now is soluble in water due to strong ion-dipole forces of attraction.
In acidic medium, benzoic acid becomes insoluble. The increase in concentration of H+ ions will shift the position of equilibrium of dissociation of benzoic acid to the left, causing benzoic acid to be hardly soluble in acidic medium.
Always remember in case of benzoic acids derivatives
Any group present at ortho position increases the acidity of benzoic acid, irrespective of its nature.
This is due to the ortho effect. When a group is present at ortho position steric factors comes into picture due to which the carboxylic acid group tends to go out of the plane of benzene due to which it's resonance stabilization is inhibited.
Always remember in case of benzoic acids derivatives
Any group present at ortho position increases the acidity of benzoic acid, irrespective of its nature.
This is due to the ortho effect. When a group is present at ortho position steric factors comes into picture due to which the carboxylic acid group tends to go out of the plane of benzene due to which it's resonance stabilization is inhibited.
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Write out the acid base reaction in each case. Which has the greatest driving force to dissolve benzoic acid?
Write out the acid base reaction in each case. Which has the greatest driving force to dissolve benzoic acid?
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Benzoic Acid partially ionises as benzoate ion and Hydrogen ion as given below.
C6H5-COOH ———->> C6H5-COO- +H+
In alkaline medium the above equilibrium shifts toward the right and the ionisation of Benzoic Acid increases. The H+ ion formed is neutralised by the OH- ion present in the Alkaline solution and thus making it more SOLUBLE.
On the contrast in acidic medium the equilibrium shifts towards the left ,thus reducing the ionisation of Benzoic Acid. So either in Acidic or neutral medium It is less soluble.
Benzoic Acid partially ionises as benzoate ion and Hydrogen ion as given below.
C6H5-COOH ———->> C6H5-COO- +H+
In alkaline medium the above equilibrium shifts toward the right and the ionisation of Benzoic Acid increases. The H+ ion formed is neutralised by the OH- ion present in the Alkaline solution and thus making it more SOLUBLE.
On the contrast in acidic medium the equilibrium shifts towards the left ,thus reducing the ionisation of Benzoic Acid. So either in Acidic or neutral medium It is less soluble.
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In benzoic acid phenyl group act as a electron donating group which causes -I effect in benzoic acid due to which electron density on Oxygen atom of carboxylic acid group is increased and hence removal of Acidic Hydrogen becomes difficult. That is why benzoic acid is less acidic.
On the other hand formic acid has no such type of group which can donate electron or withdraw electron so removal of Acidic Hydrogen from formic acid becomes easy as compared to benzoic acid so it is more acidic then benzoic acid.
Plz upvote and comment if you found this answer helpful.
In benzoic acid phenyl group act as a electron donating group which causes -I effect in benzoic acid due to which electron density on Oxygen atom of carboxylic acid group is increased and hence removal of Acidic Hydrogen becomes difficult. That is why benzoic acid is less acidic.
On the other hand formic acid has no such type of group which can donate electron or withdraw electron so removal of Acidic Hydrogen from formic acid becomes easy as compared to benzoic acid so it is more acidic then benzoic acid.
Plz upvote and comment if you found this answer helpful.
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Benzoic acid is first and foremost a weak acid and thus dissociates partially in water:
C6H5COOH + H2O <---> C6H5COO- + H3O+
From this equation and the structure of benzoic acid, you can tell three things:
This is because even though water can form hydrogen bonds with the carboxylate functional group, the bulk of the benzoic acid is still the large benzene ring, which can only form Van der Waals forces of attraction with water (significantly weaker than hydrogen bonding). Also, even though benzoic acid can dissociate in water, as it is a weak acid, it can only dissociate partially, which is insufficient to dissolve benzoic acid. Thus, benzoic acid is insoluble in cold water.
However, as temperature increases, more energy is present to overcome the hydrogen bonding between water molecules to form weaker Van der Waals forces of attraction between benzoic acid and water. Also, more energy is present to drive the dissociation of benzoic acid forward, as it is endothermic, thus benzoic acid becomes more soluble in hot water.
Benzoic acid is first and foremost a weak acid and thus dissociates partially in water:
C6H5COOH + H2O <---> C6H5COO- + H3O+
From this equation and the structure of benzoic acid, you can tell three things:
This is because even though water can form hydrogen bonds with the carboxylate functional group, the bulk of the benzoic acid is still the large benzene ring, which can only form Van der Waals forces of attraction with water (significantly weaker than hydrogen bonding). Also, even though benzoic acid can dissociate in water, as it is a weak acid, it can only dissociate partially, which is insufficient to dissolve benzoic acid. Thus, benzoic acid is insoluble in cold water.
However, as temperature increases, more energy is present to overcome the hydrogen bonding between water molecules to form weaker Van der Waals forces of attraction between benzoic acid and water. Also, more energy is present to drive the dissociation of benzoic acid forward, as it is endothermic, thus benzoic acid becomes more soluble in hot water.
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