Ammonium acetate

Ammonium acetate
IUPAC name Ammonium ethanoate
Identifiers
CAS number	631-61-8 Y
ChemSpider	11925 Y
UNII	RRE756S6Q2 Y
RTECS number	AF3675000
Jmol-3D images	Image 1
SMILES O=C(O)C.N
InChI InChI=1S/C2H4O2.H3N/c1-2(3)4;/h1H3,(H,3,4);1H3 Y Key: USFZMSVCRYTOJT-UHFFFAOYSA-N Y InChI=1/C2H4O2.H3N/c1-2(3)4;/h1H3,(H,3,4);1H3 Key: USFZMSVCRYTOJT-UHFFFAOYAY
Properties
Molecular formula	C2H3O2NH4
Molar mass	77.0825 g/mol
Appearance	white solid crystals deliquescent
Density	1.17 g/cm3[1]
Melting point	114 °C, 387 K, 237 °F
Boiling point	decomposes
Solubility in water	148 g/100 ml (4 °C)
Solubility in methanol	7.89 g/100 mL (15 °C)
Structure
Crystal structure	orthorhombic
Hazards
MSDS	JT Baker
GHS pictograms	[2]
GHS hazard statements	H315, H319, H335[2]
GHS precautionary statements	P261, P305+351+338[2]
NFPA 704	1 2 1
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ammonium acetate is a chemical compound with the formula CH₃COONH₄ (or C₂H₄O₂.NH₃ or C₂H₇NO₂). It is a white solid, which can be derived from the reaction of ammonia and acetic acid. It is available commercially and, depending on grade, can be rather inexpensive.

Uses and distinctive properties

Ammonium acetate

As the salt of a weak acid and a weak base, ammonium acetate has a number of distinctive properties.

• NH₄C₂H₃O₂ is occasionally employed as a biodegradable de-icing agent.
• It is often used with acetic acid to create a buffer solution, one that can be thermally decomposed to non-ionic products
• Ammonium acetate is useful in the Knoevenagel condensation in organic synthesis.
• It is a relatively unusual example of a salt that melts at low temperatures.
• Can be used with distilled water to make a protein precipitating reagent.
• Is often used as an aqueous buffer for ESI mass spectrometry of proteins and other molecules.

Ammonium acetate is volatile at low pressures. Because of this it has been used to replace cell buffers with non-volatile salts, in preparing samples for mass spectrometry. ^[3] It is also popular as a buffer for mobile phases for HPLC with ELSD detection for this reason. Other volatile salts which have been used for this include ammonium formate.

Food Additive

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.^[4]

Properties

CH₃COONH₄ is hygroscopic. It decomposes easily at elevated temperatures into acetamide.

CH₃COONH₄ → CH₃C(O)NH₂ + H₂O

In this reaction, a salt is converted to two molecular species, which is a relatively uncommon conversion at mild temperatures.

References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
2. ^ ^{a b c} Online Sigma Catalogue , accessdate: June 8, 2011.
3. ^ Berman et al., 2008. J Am Soc Mass Spectrom, 19:1230-1236.
4. ^ Australia New Zealand Food Standards Code"Standard 1.2.4 - Labelling of ingredients". http://www.comlaw.gov.au/Details/F2011C00827. Retrieved 2011-10-27. 

Further reading

• G. Jones, Organic Reactions, 1967, volume 15, 204ff (the Knoevenagel Reaction)