Zinc acetate

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Zinc acetate
Zinc acetate dihydrate sample.jpg
Sample of zinc acetate dihydrate
Names
IUPAC name
Zinc acetate
Other names
Acetic acid, zinc salt
Acetic acid, zinc(II) salt
Dicarbomethoxyzinc
E650
Zinc(II) acetate
Zinc diacetate
Properties
Zn(CH3COO)2 (anhydrous)
Zn(CH3COO)2·2 H2O (dihydrate)
Molar mass 183.48 g/mol (anhydrous)
219.50 g/mol (dihydrate)
Appearance Colorless crystalline solid
Odor Slightly acetic
Density 1.735 g/cm3 (dihydrate)
Melting point 100 °C (212 °F; 373 K) (dihydrate, decomposition)
237 °C (459 °F; 510 K) (anhydrous, decomposition)
Boiling point Decomposes
dihydrate:
43 g/100 ml (20 °C)
Solubility Slightly soluble in 1,4-Dioxane, acetic acid, acetic anhydride, acetyl chloride, acetone, aniline, benzonitrile, butanol, dimethyl sulfate, dimethylformamide, epichlorohydrin, ethanol, methanol, methyl propionate, pyridine, THF
Almost insoluble in liq. ammonia
Insoluble in bromoacetic acid, liq. SO2, toluene, xylene
Solubility in acetic acid 0.293566 g/cm3 (at 25 °C)
Solubility in ethanol 0.495393 g/cm3 (at 25 °C)
Hazards
Safety data sheet Alfa Aesar (anydrous)
FisherScientific (dihydrate)
Related compounds
Related compounds
Copper(II) acetate
Cadmium acetate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Zinc acetate is a chemical compound with the formula Zn(CH3COO)2 the acetic acid salt of zinc, more commonly encountered as dihydrate, Zn(CH3COO)2·2 H2O.

It is also used as food additive, E650.

Properties

Chemical

Zinc acetate reacts with bases to form insoluble zinc hydroxide:

Zn(CH3COO)2 + 2 NaOH → 2 CH3COONa + Zn(OH)2

According to one paper, pyrolysis of anhydrous zinc acetate (at reduced pressure) should yield acetic anhydride and leave behind basic zinc acetate:

2 Zn(AcO)2 → Zn4(AcO)6 + Ac2O

So far this route has not been confirmed.

Physical

Zinc acetate is a solid crystalline, soluble in water. Its anhydrous form is hygroscopic and quickly turns into the dihydrate form upon standing in open air. It has a weak acetic smell.

Availability

Zinc acetate is available as food supplements and can be purchased online. Recrystallization is required to purify the compound.

Higher purity Zn(AcO)2 can be purchased from chemical suppliers.

Preparation

Zinc acetate can be prepared by adding zinc metal or zinc oxide to acetic acid. Vinegar can also be used as source acetic acid. After all the zinc has dissolved, the solution is concentrated and cooled to crystallize solid zinc acetate dihydrate. If vinegar was used, organic residue from the vinegar will be trapped in the zinc acetate crystals. To remove the impurities, crush the resulting crystals and wash them thoroughly with an organic solvent.

If anhydrous zinc acetate is desired, you can dry the zinc acetate dihydrate by refluxing it with toluene using a Dean-Stark apparatus.

Projects

  • Grow crystals
  • Make zinc metal
  • Make glacial acetic acid
  • Synthesis of acetic anhydride

Handling

Safety

Zinc acetate is slightly irritant due to the acetic acid resulting from hydrolysis, though this is not a problem when handling the compound.

Storage

Zinc acetate should be stored in closed bottles, away from moisture and acids, in a well ventilated place.

Anhydrous zinc acetate should be kept in air-tight containers.

Disposal

No special disposal is required for zinc acetate, though it's best to dilute it strongly if you want to pour it down the drain. Alternatively, you can precipitate zinc hydroxide/oxide by adding an alkali to a solution of zinc acetate.

References

Relevant Sciencemadness threads