Are anhydrous compounds are just the concentrated form of hydrated compounds? Or do they really pose a chemical significance during synthesis reaction? Is it acceptable to use anhydrous compounds in place of hydrated compounds by just reducing the concentration?
Lokesh Murali
Yes, of course they have chemical significance during synthesis, you need to use anhydrous compounds when:
- Synthesising water sensitive compounds
- While using a water sensitive reactant or catalyst
Using hydrated compound instead of the anhydrous one really depends on the synthesis you are trying to do, if the product, reactant and catalyst are not water sensitive then yes you can use it, but if one of them is water sensitive you cant use hydrated compounds in that case.
A hydrate has different physicochemical properties than the anhydrous form. It affects the solubility and stability of the compound. Depending on your goal, you can target on or the other. Usually, the most stable form is targeted; however, in different reactions it is sometimes required the anhydrous form as Lokesh mentioned. If you will use it in solution, than it does not matter the form.
Oussama Kheireddine Nehar Thank you for your reply, if we add water to oxalic acid (anhydrous) does it provide us with oxalic acid dihydrate?
Lokesh Murali
oxalic acid usually exists as oxalic acid dihydrate
So, theoretically yes its possible, you can obtain the dehydrate form by recrystallising anhydrous oxalic acid in water or mixture of water and ethanol
Dear Lokesh Murali ,If you are using your anhydrous compound in the place of hydrated compound for a reaction, I do not see a significant problem. Most reactions that you use hydrated compound does not require anhydrous conditions. However the other way around will be problematic . If your reaction requires anhydrous conditions, using hydrated compound instead of anhydrous material will cause significant issues. On such situation, J would highly recommend you to remove water from the hydrated version by freeze drying if possible. I’m not quite sure how efficient the crystallization will be here to remove water content from the compound , if Crystallization requires an aqueous media.
Chathura S. Abeywickrama
in his late question its the other way around, he wanted hydrated compound out of anhydrous compound.
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