Ammonium acetate
Names IUPAC name Identifiers ChEBI ChemSpider ECHA InfoCard 100.010.149 EC Number RTECS number UNII UN number 3077 Properties C2H7NO2 Molar mass 77.083 g·mol−1 Appearance White solid crystals, deliquescent Odor Slightly acetic acid like Density 1.17 g/cm3 (20 °C)[1] 1.073 g/cm3 (25 °C) Melting point 113 °C (235 °F; 386 K)[4] 102 g/100 mL (0 °C) 148 g/100 mL (4 °C)[1] 143 g/100 mL (20 °C) 533 g/100 mL (80 °C) Solubility Soluble in alcohol, SO2, acetone, liquid ammonia[2] Solubility in methanol 7.89 g/100 mL (15 °C)[3][1] 131.24 g/100 g (94.2 °C)[2] Solubility in dimethylformamide 0.1 g/100 g[2] Acidity (pKa) 9.9 Basicity (pKb) 33 −41.1·10−6 cm3/mol Viscosity 21 Structure Orthorhombic Thermochemistry −615 kJ/mol[2] Hazards Occupational safety and health (OHS/OSH): Irritant GHS labelling:[3] Warning H303, H316, H320, H333 P281, P335 NFPA 704 (fire diamond) Flash point 136 °C (277 °F; 409 K)[3] Lethal dose or concentration (LD, LC): 386 mg/kg (mice, intravenous)[2] Safety data sheet (SDS) JT Baker
Ammonium acetate, also known as spirit of Mindererus in aqueous solution, is a chemical compound with the formula NH4CH3CO2. It is a white, hygroscopic solid and can be derived from the reaction of ammonia and acetic acid. It is available commercially.[5]
The synonym Spirit of Mindererus is named after R. Minderer, a physician from Augsburg.[6]
It is the main precursor to acetamide:[7]
NH4CH3CO2 → CH3C(O)NH2 + H2O
It is also used as a diuretic.[5]
As the salt of a weak acid (ammonium) and a weak base (acetate), is often used to create a buffer solution. Ammonium acetate is volatile at low pressures. Because of this, it has been used to replace cell buffers that contain non-volatile salts in preparing samples for mass spectrometry.[8] It is also popular as a buffer for mobile phases for HPLC with ELSD and CAD-based detection for this reason. Other volatile salts that have been used for this include ammonium formate.
When dissolving ammonium acetate in pure water, the resulting solution typically has a pH of 7, because the equal amounts of acetate and ammonium neutralize each other. However, ammonium acetate is a dual component buffer system, which buffers around pH 4.75 ± 1 (acetate) and pH 9.25 ± 1 (ammonium), but it has no significant buffer capacity at pH 7, contrary to common misconception.[9]
- a biodegradable de-icing agent.
- a catalyst in the Knoevenagel condensation and as a source of ammonia in the Borch reaction in organic synthesis.
- a protein precipitating reagent in dialysis to remove contaminants via diffusion.
- a reagent in agricultural chemistry for determination of soil CEC (cation exchange capacity) and determination of available potassium in soil wherein the ammonium ion acts as a replacement cation for potassium.
- part of Calley’s method for lead artifact conservation
Ammonium acetate is also used as a food additive as an acidity regulator; INS number 264. It is approved for usage in Australia and New Zealand.[10]
Ammonium acetate is produced by the neutralization of acetic acid with ammonium carbonate or by saturating glacial acetic acid with ammonia.[11] Obtaining crystalline ammonium acetate is difficult on account of its hygroscopic nature.