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Acetic Acid


Other Names:

Glacial acetic acid

Ethanoic acid






General Information:


Structure:



CAS Number: 64-19-7

Molecular Weight: 60.05 g/mol

Appearance: Colorless liquid

Chemical Formula: CH3CO2H

Melting Point: 16-17 C

Boiling Point: 118-119 C

Density: 1.049 g/mL at 25 C

Acidity (pKa): 4.76


The common name for undiluted acetic acid is glacial acetic acid. With a melting/freezing point of around 16 C, acetic acid is not a suitable solvent for reactions that require cooling. In fact, when removing acetic acid by rotovap it tends to crystallize on the cold finger of the rotovap rather than dripping into the collection flask as a liquid.


Acetic acid is sometimes used as a polar protic solvent. When it is used as a solvent, it is often used for reactions that involve carbocation intermediates.


Acetic acid is a weak monoprotic acid and has a pKa of 4.76. As a weak acid, acetic acid is sometimes used to quench basic reactions, or to adjust the pH of a mixture.




Common Uses:


Solvent in nitration reactions





Reagent/catalyst in reductive aminations





Solvent/co-solvent in the iron catalyzed reduction of nitro groups





Solvent in brominations (especially alpha-bromination)





Reagent for quenching reactions



Procedure excerpt:

…stirred at RT for 30 min. The mixture was quenched with AcOH (0.45 mL) and concentrated in vacuo. The resulting material was purified…




Acid for adjusting pH



Procedure excerpt:

…The reaction mixture was cooled to RT and concentrated in vacuo. The mixture was diluted with H2O, acidified with AcOH, and extracted with EtOAc




Additive in HPLC purifications



Procedure excerpt:

…in DMSO (0.9 mL) was heated to 120 C overnight. The crude product was filtered and purified by HPLC (H2O/ACN with AcOH)…




Reagent for forming acetate salts of compounds



Procedure excerpt:

…added AcOH (28.9 g, 0.480 mol). The mixture was concentrated in vacuo (maintaining the temp below 50 C) to provide the product as the carboxylate acetic acid salt…




Safety:


Concentrated acetic acid (AcOH) is corrosive to the skin. Nitrile gloves have been shown to provide much better protection against acetic acid compared to latex gloves.




References:


1) WO2014149164, page 386

2) WO2007084786, page 112

3) WO2011014535, page 39

4) WO2011017578, page 154

5) WO2015129926, page 108

6) WO2012069948, page 63

7) WO2010016005, page 84

8) WO2011017578, page 127

9) Wikipedia: Acetic acid (link)

10) www.sigmaaldrich.com: Glacial acetic acid (link)

11) www.emdmillipore.com: Acetic acid (glacial) 100% (link)