[Chemistry] questions on solubilty of bases and naphthalen-2-ol

[xechox_06]

Homework Statement

2-hydroxybenzenediazonium ion is allowed to react with naphthalen-2-ol to form 1-(4-hydroxyphenylazo)-2-naphthol

Homework Equations

1.Why is amine having a different solubility in water and dilute hydrochloric acid?

2.Why is naphthalen-2-ol dissolves in sodium hydroxide instead of water or acidic aqueous solvent?

3.Does naphthalen-2-ol react with aliphatics amines and how to use it to distinguish between aliphatics and aromatic amines?

The Attempt at a Solution

1.I guess it is because when it dissolve in dilute hydrochloric acid, the H+ ions react with the OH- ions from the amine, so the equilibrium shift towards the right, and therefore amine dissolves better in dilute hydrochloric acid?

2.Is it related to basify...but I even don't know what is basify. Or it is because naphthalen-2-ol is too bulky to dissolve in water?

3.My guess is no. But I also don't know why...

Really thanks a lot for you guys help

 

[chemisttree]

1. What happens to an amine in acidic solution? It has nothing to do with the alcohol (-OH) functionality...

2. Think of naphthalene-2-ol as an enol. What would a base do in that case?

3. To answer this question you need to understand the mechanism of the reaction. Remember that the diazonium salt is added slowly to a solution that contains an excess of NaOH, so the reaction occurs under basic conditions. Diazonium ion is an electrophile in this reaction.

 

[Blueshift5]

I would like to provide a response to the questions on solubility of bases and naphthalen-2-ol.

1. The difference in solubility of amines in water and dilute hydrochloric acid can be explained by their acidic and basic properties. Amines are basic compounds and can readily react with acids such as hydrochloric acid to form water-soluble salts. In water, the amine may also form hydrogen bonds with water molecules, making it more soluble. However, in dilute hydrochloric acid, the acidic properties of the acid can protonate the amine, making it more water-soluble.

2. The solubility of naphthalen-2-ol in sodium hydroxide can be attributed to its acidic properties. Naphthalen-2-ol is a weak acid and can react with the strong base, sodium hydroxide, to form a water-soluble salt. In contrast, in an acidic aqueous solvent, naphthalen-2-ol may not be as soluble due to competing protonation reactions.

3. Naphthalen-2-ol may not react with aliphatic amines as it is primarily an aromatic compound. However, it can be used to distinguish between aliphatic and aromatic amines based on their reactivity with naphthalen-2-ol. Aromatic amines, such as 2-hydroxybenzenediazonium ion, can undergo diazotization reactions with naphthalen-2-ol to form azo compounds, while aliphatic amines may not exhibit this reaction. This can be used as a distinguishing test for aromatic and aliphatic amines.