Sciencemadness Discussion Board

Propan2ol + NaOH

Romix - 2-4-2016 at 00:48

Added 3 spoon of NaOH to anhydrous isopropanol.
5 - 10 minuts all of it solidified, crystallized.

Added another 100ml, checked hour later, solid crystals(soluble in water)



Romix - 2-4-2016 at 00:49

Would same happen with ethanol?

Neuro- - 2-4-2016 at 08:23

Yes, as long as your ethanol was anhydrous, although yields wouldn't be great.
https://en.wikipedia.org/wiki/Sodium_ethoxide

BromicAcid - 2-4-2016 at 10:05

Dissolution of NaOH/KOH in simple alcohols is exothermic, it doesn't take much KOH to make MeOH boil on addition. Of course, as the solvent heats up it dissolves more of the hydroxide until everything is in solution. Then your solution cools and you crash out your hydroxide. Some will form the alkoxide in equilibrium with the alchohol but I would think that most of what you are seeing is unreacted NaOH.

What size were these spoon fulls? Heaping tablespons? How much isopropanol did you have to start out with? We all have to start somewhere but I would recommend your next investment be in some measuring tools for liquids, preferably in milliliters, even plastic disposable beakers can have graduations. As it stands you don't have much to work with. Wiki says solubility is 238 g/L in MeOH, less than 139 g/L in EtOH and the trend is going to continue downward from there.

Romix - 2-4-2016 at 14:42

Quote: Originally posted by BromicAcid  
Dissolution of NaOH/KOH in simple alcohols is exothermic, it doesn't take much KOH to make MeOH boil on addition. Of course, as the solvent heats up it dissolves more of the hydroxide until everything is in solution. Then your solution cools and you crash out your hydroxide. Some will form the alkoxide in equilibrium with the alchohol but I would think that most of what you are seeing is unreacted NaOH.

What size were these spoon fulls? Heaping tablespons? How much isopropanol did you have to start out with? We all have to start somewhere but I would recommend your next investment be in some measuring tools for liquids, preferably in milliliters, even plastic disposable beakers can have graduations. As it stands you don't have much to work with. Wiki says solubility is 238 g/L in MeOH, less than 139 g/L in EtOH and the trend is going to continue downward from there.


No, its not exothermic, in anhydrous alcohols.
Compare to water. Only a lil bit.

Romix - 2-4-2016 at 14:46

Ok, what will happen on decomposition of this crystals, NaOH and isopropanol?

[Edited on 2-4-2016 by Romix]

Tsjerk - 3-4-2016 at 05:39

Quote: Originally posted by Romix  

No, its not exothermic, in anhydrous alcohols.
Compare to water. Only a lil bit.


Do you think there is a difference between lower and higher alcohols? Do you know why there is a difference between water and alcohol?

Romix - 3-4-2016 at 06:38

Quote: Originally posted by Tsjerk  
Quote: Originally posted by Romix  

No, its not exothermic, in anhydrous alcohols.
Compare to water. Only a lil bit.


Do you think there is a difference between lower and higher alcohols? Do you know why there is a difference between water and alcohol?


No.
All ols I know boils at lower temperature then water.


[Edited on 3-4-2016 by Romix]

Hegi - 3-4-2016 at 06:56

I must agree with BromicAcid. It is soluble in isopropanol and it does not react. Equilibrium is shifted to the reactants. So there´s just a minimum of isopropoxide.

There is no rule for an exothermic reaction it must boil the solvent off :)

Tsjerk - 3-4-2016 at 07:25

As far as I know there is a difference between binding affinity of the compounds with water, which has to do with the formation of hydrogen bonds. I can imaging these bonds are stronger (or less hindered) with lower alcohols.

There is no reaction between water and hydroxide either, dissolving them is exothermic though. There is a difference between sodium and potassium hydroxide however. The difference can be explained by the size and overall interaction of the ions with water.

I know that the dissolution of for example ethanol in water is exothermic, for the reason I described above. I asked the last question because I was wondering whether the same is true for isopropanol (which I think is true). I think it is true for every alcohol that is miscible with water.

Edit: Ok, there is a reaction between hydroxide and water, but that doesn't explain the exothermic reaction.

[Edited on 3-4-2016 by Tsjerk]

Tsjerk - 3-4-2016 at 08:24

The reaction between absolute ethanol and water is stronger than the reaction between 96% and water. The difference can be explained by the fact part of the hydrogen bonds already formed.

The reason azeotropes exist is because certain compounds like to bind (like water and ethanol like to bind). In this process disorder is gained. Nature always looks for chaos. This way molecules are happy. Breaking the bonds costs energy, therefore they are not happy.

Nature loves losing ordering.

Chaos is the final goal.

BromicAcid - 3-4-2016 at 08:52

Of interest to this tread in terms of alkoxides using hydroxides:

http://www.sciencemadness.org/talk/viewthread.php?tid=2656