Interesting Decomposition Behavior of Metal Acetates

FT-IR is an important tool for tracking the thermal decomposition profile of metal acetates. Using FT-IR, scientists established three molecular transformations that are generally associated with

• dehydration at 80-130C,

• formation of carbonate (or oxalate?) at 105-230C, and

• final residue formation (metal, oxide) at 100–440C.

Different metals show different molecular speciation as follows:

1. Sodium and potassium acetates decompose first to an oxalate, which decomposes and yields the metal carbonate.

2. For barium acetate the corresponding carbonate occurs directly without an intermediate.

3. Calcium acetate decomposes to the carbonate over a crystalline anhydrous modification.

4. Magnesium, lead, nickel, and cadmium acetates form an intermediate basic salt which decomposes at higher temperatures to give the metal, while magnesium acetate yields the corresponding metal oxide.

5. Copper acetate affords a pure metal as final product where the decomposition proceeds via a crystalline modification of the anhydrous acetate as the intermediate analogous to the calcium.

6. Cobalt and silver acetate decompose to the pure metal without the formation of an intermediate.

7. Zinc and manganese acetates afford crystalline acetate intermediates which decompose to the corresponding oxides.

For most metals, it should be noted that the carbonates are most common thermal decomposition intermediates which be can be transformed into the corresponding oxides at higher temperatures.

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