# Why Does Sodium Hydroxide Increase Histidine's Solubility in Water?

• fdvet91
In summary, histidine is an amino acid that is not soluble in water, but can dissolve in water when dilute sodium hydroxide is added. The reaction between histidine and dilute sodium hydroxide can be represented by the equation C6H9N3O2 + NaOH > ?, and the solubility of water changes due to an increase in pH when the sodium hydroxide is added. This reaction is a typical acid-base reaction, with histidine acting as the acid and sodium hydroxide acting as the base, resulting in the formation of a salt and water.
fdvet91

## Homework Statement

Histidine is an amino acid. It is not soluble in water but it will dissolve in water when dilute sodium hydroxide is added.

The question has two parts to it:
part-a)
Write an equation for the reaction that occurs between histidine and dilute sodium hydroxide.
part-b)
Explain why the solubility of the water changes after the sodium hydroxide is added

## Homework Equations

we are also given the structure of histidine as shown in the link
http://imageshack.us/photo/my-images/580/histidine1.gif/

## The Attempt at a Solution

i have no clue with equation work. i managed to get... C6H9N3O2 + NaOH >
cannot figure out what the product(s) is/are going to be
part-b)attempt
the ph will increase once NaOH is added but i don't see how that has anything to do with solubility. any help would be appreciated, thanks.

How does an acid react with a base?

an acid will react with a base to give salt and water

acid + base = salt +water
not sure what you mean by that though

Histidine is an aminoacid, isn't it?

Last edited:

Hello,

I would like to provide a response to the content you have provided. First, let's start with the equation for the reaction between histidine and dilute sodium hydroxide.

C6H9N3O2 + NaOH → C6H9N3O2Na + H2O

The product formed in this reaction is sodium histidine, which is soluble in water. This is why the solubility of histidine increases when dilute sodium hydroxide is added.

Now, let's discuss why the solubility of histidine increases with the addition of sodium hydroxide. This is due to the basic nature of sodium hydroxide. When it is added to water, it dissociates into sodium ions (Na+) and hydroxide ions (OH-). The hydroxide ions can react with the carboxylic acid group (-COOH) of histidine, forming a salt (C6H9N3O2Na) and water. This salt is more soluble in water compared to histidine, which is why the overall solubility of the solution increases.

I hope this explanation helps clarify the concepts for you. If you have any further questions, please don't hesitate to ask. Keep up the good work in your organic chemistry studies!

## 1. What is the role of histidine in organic chemistry reactions?

Histidine is an amino acid that plays a crucial role in many organic chemistry reactions. It can act as a nucleophile, a base, a proton shuttle, and a buffer, making it a versatile molecule in various biochemical processes.

## 2. How does histidine affect enzyme-catalyzed reactions?

Histidine residues often act as catalytic sites in enzymes, helping to facilitate chemical reactions by stabilizing intermediates and lowering activation energy. They also play a role in substrate binding and orientation.

## 3. What is the pKa value of histidine and why is it important?

The pKa value of histidine is approximately 6, making it a weakly acidic amino acid. This property allows it to act as a proton donor or acceptor, making it important in pH-dependent reactions and as a buffer in biological systems.

## 4. Can histidine participate in redox reactions?

While histidine itself is not a redox-active molecule, it can participate in redox reactions indirectly by serving as a ligand for metal ions, which can undergo redox reactions. It can also act as a redox mediator in certain enzymatic reactions.

## 5. How is histidine involved in protein folding and stability?

Histidine residues can form hydrogen bonds with other amino acid residues, contributing to the three-dimensional structure and stability of proteins. It can also participate in non-covalent interactions with other molecules, such as heme groups, which can affect protein folding and function.

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