2 replies to this topic

[EdgarAB]

The reaction:
MgO
2C17H35COOH ====== (C17H35COO)2Mg

1.) MgO is intrinsically basic and is a good catalyst for this reaction.
2.) Will it further favor the forward reaction if the environment is basic?
3.) What pH level of the environment is required for the forward reaction not to proceed?

Hope someone would be kind enough to answer these questions.

Thanks and best regards.

[Andrei]

EdgarAB,

I do not have direct experience with Magnesium Stearate, but I have some very old experience with Calcium, Stannum (Tin) and Cadmium Stearates.
It was a very long time ago, but I remember that no direct Metal Oxide-Stearic Acid reaction was happening, always the corresponding oxide (salt) was first transformed in hydroxide, and only after that contacted with the fatty acid. Maybe somebody did use oxides in a lab somewhere, but in the real world we were manufacturing the metallic stearates that way (via a hydroxide). Maybe this will give you some indication about what pH value drives the reaction. And by the way, everything was happening in a water environment.
From the little chemistry I know I had the impression that, as a general rule, metal oxides are some of the most stable compounds existing, meaning very low reactivity. Probably it is not a coincidence that some of the metals naturally can be found as metal oxides on our planet.
I do not understand how MgO can be a catalyst in a reaction where Mg is consumed and leaves the system as a product. According to my understanding a catalyst, at least theoretically, is not consumed in the reaction.
The way you are showing the chemical reaction “pH” term is meaningless, there is no H+ around to be able to actually express a pH. You cannot speak about pH unless there is a solution in the middle. I think water is missing there and a base, a very strong base.
All the best.

[pawan]

The reaction proposed by you is incomplete & incorrect also.
Andrei has correctly pointed out that it is done using hydroxide compounds with
Fatty acids.
We are manufacturing some metal stearates using OH form.

So you need to react Mg(OH)2 with fatty alcohols producing water in the system
& hence pH comes in picture.......

At the end it will be slightly basic which can be neutralized with weak acid if required
depending on product specs for your customer.

There is no catalyst thing & there is no forward reaction after this.
You just add stoichiometric amounts based on purity of commercial samples.