Ammonium acetate
Overview
 
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
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

. It is available commercially and, depending on grade, can be rather inexpensive.
As the salt of a weak acid and a weak base, ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

 acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

 has a number of distinctive properties.
  • NH4C2H3O2 is occasionally employed as a biodegradable de-icing agent.
  • It is often used with acetic acid
    Acetic acid
    Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

     to create a buffer solution
    Buffer solution
    A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a...

    , one that can be thermally decomposed to non-ionic products
  • Ammonium acetate is useful in the Knoevenagel condensation
    Knoevenagel condensation
    The Knoevenagel condensation reaction is an organic reaction named after Emil Knoevenagel. It is a modification of the Aldol condensation.A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule...

     in organic synthesis
    Organic synthesis
    Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

    .
  • 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
    Electrospray ionization
    Electrospray ionization is a technique used in mass spectrometry to produce ions. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized...

     mass spectrometry
    Mass spectrometry
    Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

     of protein
    Protein
    Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

    s and other molecules.

Ammonium acetate is volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

 at low pressures.
Encyclopedia
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
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

. It is available commercially and, depending on grade, can be rather inexpensive.

Uses and distinctive properties

As the salt of a weak acid and a weak base, ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

 acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

 has a number of distinctive properties.
  • NH4C2H3O2 is occasionally employed as a biodegradable de-icing agent.
  • It is often used with acetic acid
    Acetic acid
    Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

     to create a buffer solution
    Buffer solution
    A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a...

    , one that can be thermally decomposed to non-ionic products
  • Ammonium acetate is useful in the Knoevenagel condensation
    Knoevenagel condensation
    The Knoevenagel condensation reaction is an organic reaction named after Emil Knoevenagel. It is a modification of the Aldol condensation.A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule...

     in organic synthesis
    Organic synthesis
    Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

    .
  • 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
    Electrospray ionization
    Electrospray ionization is a technique used in mass spectrometry to produce ions. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized...

     mass spectrometry
    Mass spectrometry
    Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

     of protein
    Protein
    Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

    s and other molecules.

Ammonium acetate is volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

 at low pressures. Because of this it has been used to replace cell buffers with non-volatile salts, in preparing samples for mass spectrometry. It is also popular as a buffer for mobile phases for HPLC
High-performance liquid chromatography
High-performance liquid chromatography , HPLC, is a chromatographic technique that can separate a mixture of compounds and is used in biochemistry and analytical chemistry to identify, quantify and purify the individual components of the mixture.HPLC typically utilizes different types of stationary...

 with ELSD detection for this reason. Other volatile salts which have been used for this include ammonium formate
Ammonium formate
Ammonium formate, NH4HCO2, is the ammonium salt of formic acid. It is a colorless, hygroscopic, crystalline solid.-Uses:Pure ammonium formate decomposes into formamide and water when heated, and this is its primary use in industry...

.

Food Additive

Ammonium acetate is also used as a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

 as an acidity regulator; INS number 264. It is approved for usage in Australia and New Zealand.

Properties

CH3COONH4 is hygroscopic. It decomposes easily at elevated temperatures into acetamide
Acetamide
Acetamide is an organic compound with the formula CH3CONH2. It is the simplest amide derived from acetic acid. It finds some use as a plasticizer and as an industrial solvent...

.
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.

Further reading

  • G. Jones, Organic Reactions, 1967, volume 15, 204ff (the Knoevenagel Reaction)
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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