What is the molecular formula of vinegar

acetic acid

Acetic acid is one of the simplest carboxylic acids and belongs to the class of organic compounds. Its systematic name is ethanoic acid. The empirical formula is C2H4O2. It can also be described in more detail than CH3–Write COOH.

View: Start the Jsmol visualization by clicking the link under the acetic acid molecule. Look at the molecule in the ball-and-stick representation, the space-filling representation, and the bond-only representation.

structure

The molecule is structured as expected. At the carbon atom of the CH3–Group it is tetrahedrally coordinated, on the other carbon atom it is trigonal planar and on the oxygen atom it is angled.

properties

Acetic acid has a melting point of 16.6 ° C. For such a small molecule, that's a remarkably high melting point.

Acetic acid has a pKa-Value of 4.76. Compared to the strong mineral acids such as sulfuric acid, hydrochloric acid or nitric acid, this is a low value. Acetic acid is therefore viewed as a weak acid. However, many organic acids are even weaker than acetic acid, so it is one of the stronger acids in this group.

  • more about the reasons why acetic acid is expected to have a lower melting point, and why it does have such a high melting point - coming soon.
  • more about the reasons acetic acid is one of the stronger organic acids - coming soon.

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Manufacturing

Acetic acid is one of the oldest man-made substances. Even the ancient Egyptians could make vinegar. You simply leave wine open for a long time. Acetic acid bacteria (Acetobacter aceti and others), which occur everywhere, are introduced into the wine standing around and begin their metabolic activity. They convert the alcohol (ethanol) into acetic acid. Of course, this procedure is not all that effective. The conversion proceeds only slowly, and at an acetic acid concentration of 12% it is over - then the acetic acid bacteria are poisoned by their metabolic products (acetic acid).

The process of vinegar fermentation just described has been further developed over time. The principle is always that liquids containing ethanol (they are called mash) are mixed with acetic acid bacteria. Then air is passed through at an elevated temperature. Just like 4000 years ago, the bacteria now do their work, only faster. Despite all the improvements, vinegar fermentation is complex and expensive. That is why today only table vinegar is produced in this way, around 190,000 t per year worldwide (as of 2010).
Reaction equation of vinegar fermentation: C2H5OH + O2 → CH3COOH + H2O
This reaction provides energy. This also gives you the answer to the question you may have already asked why the vinegar bacteria actually convert ethanol into acetic acid.

Most of the acetic acid (around 7 million tons per year) is produced industrially. In the presence of a rhodium-containing catalyst, methanol and carbon monoxide react at a temperature of 150 to 200 ° C. and a pressure of 30 to 60 bar to form acetic acid.
Reaction equation: CH3OH + CO → CH3COOH

About a quarter of acetic acid is made through recycling. Wastewater that arises from the production of vinyl acetate and cellulose acetate is processed.

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use

Only about 3% of the acetic acid produced worldwide is used as table vinegar (that is a 5% acetic acid) or vinegar essence (25%). What do you do with the big rest?

  • Most of the acetic acid is converted into vinyl acetate (vinyl acetate), which then reacts to form polyvinyl acetate. Polyvinyl acetate is used as a binder for paints and varnishes and as a solvent for adhesives, also in the paper and textile industries.
  • Another significant proportion of acetic acid is converted into acetic anhydride. Cellulose acetate (acetyl cellulose) can be produced from this by reacting it with cellulose, which is then further processed into textile fibers (“artificial silk”), glasses frames, cigarette filters and other things. Since acetic anhydride can also be used to produce heroin, it is subject to the Basic Substance Monitoring Act in Germany.
  • About 5 to 10% of the world's acetic acid production is used as a solvent in the manufacture of terephthalic acid, which is further processed into polyethylene terephthalate (PET), which is often sold in bottle form.
  • Acetic acid salts are used as preservatives for food. They are sodium acetate (E 262), potassium acetate (E 261) and calcium acetate (E 263).
  • Acetic acid itself is used as an acidifier for food (E 260).
  • Household applications are of little importance in terms of quantity. This includes the use as a cleaning agent for limescale deposits. Acetic acid reacts with the lime to form water-soluble calcium acetate. However, acetic acid must not be used on metal surfaces, as these are also attacked. When washing clothes, a dash of vinegar is an inexpensive and environmentally friendly substitute for the fabric softener that is otherwise added to the final rinse water.

more information on acetic acid

There are now a lot of good sites on the internet about acetic acid, for example

Physical Properties

  • Melting point: 16.6 ° C
  • Boiling point: 117.9 ° C
  • Density at 20 ° C: 1.0492 g / cm3
  • Viscosity at 20 ° C: 1.22 ⋅ 10–3 ⋅ N ⋅ s / m2
  • pKaValue: 4.76
  • CAS no. : 64-19-7

 

 

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