ORGANIC ACIDS

Organic acids are organic compounds that have a degree of acidity (English: acidic properties). The most common organic acids are the alkanoic acid having acidity with carboxyl-COOH, and sulfonic acid group-SO2OH the acidity has a relatively stronger. Stability is very important to the acid groups and determine the degree of acidity an organic compound. 

In biology, there is an acidic group with low acidity, such as the-OH,-SH, enol group, phenol group. Bio-organic compounds such groups are not classified as organic acids. Examples of these compounds include: lactic acid, acetic acid, formic acid, citric acid and oxalic acid. 

Acetic acid, ethanoic acid or acetic acid is an organic acid chemical compounds known as sour flavoring and aroma in food. Acetic acid has the empirical formula C2H4O2. This formula is often written in the form of CH3-COOH, CH3COOH, or CH3CO2H. Pure acetic acid (called glacial acetic acid) is a colorless hygroscopic liquid, and has a freezing point of 16.7 ° C. 

Acetic acid is one of the simplest carboxylic acids, as formic acid. Solution of acetic acid in water is a weak acid, meaning that only partially dissociate into H and CH3COO-ions. Acetic acid is a chemical reagent and industrial raw materials is important. Acetic acid is used in the production of polymers such as polyethylene terephthalate, cellulose acetate and polyvinyl acetate, as well as a wide range of fibers and fabrics. In the food industry, acetic acid is used as an acidity regulator. In households, diluted acetic acid is often used as a water softener. Within a year, world demand for acetic acid to 6.5 million tons per year. 1.5 million tons per year generated from the recycling, the remainder derived from the petrochemical industry as well as from biological sources.

Vinegar (Acetic Acid)
Acetic acid, ethanoic acid or acetic acid is an organic acid chemical compounds known as sour flavoring and aroma in food. Acetic acid has the empirical formula C2H4O2. This formula is often written in the form of CH3-COOH, CH3COOH, or CH3CO2H. Pure acetic acid (called glacial acetic acid) is a colorless hygroscopic liquid, and has a freezing point of 16.7 ° C.
Acetic acid is one of the simplest carboxylic acids, as formic acid. Solution of acetic acid in water is a weak acid, meaning that only partially dissociate into H + and CH3COO-. Acetic acid is a chemical reagent and industrial raw materials is important. Acetic acid is used in the production of polymers such as polyethylene terephthalate, cellulose acetate and polyvinyl acetate, as well as a wide range of fibers and fabrics. In the food industry, acetic acid is used as an acidity regulator. In households, diluted acetic acid is often used as a water softener. Within a year, world demand for acetic acid to 6.5 million tons per year. 1.5 million tons per year generated from the recycling, the remainder derived from the petrochemical industry as well as from biological sources.
Naming
Acetic acid is a trivial name or trade name of this compound, and is the name most recommended by IUPAC. The name is derived from the Latin word acetum, meaning vinegar. Systematic name of this compound is ethanoic acid. Glacial acetic acid is a trivial name that refers to acetic acid which is not mixed with water. So called because water-free acetic acid forms crystals resemble ice at 16.7 ° C, slightly below room temperature.
The most commonly used abbreviations and acronyms merupakat official for acetic acid is AcOH or HOAc where Ac means an acetyl group, CH3-C (= O) -. In the context of acid-base, acetic acid is often abbreviated HAC, though many feel that the abbreviation is not true. Ac also not be confused with the symbol of the element actinium (Ac).
History
Vinegar has been known to humans since ancient times. Vinegar is produced by a variety of bacteria producing acetic acid, and acetic acid is a byproduct of the manufacture of beer or wine.
The use of acetic acid as chemical reagent has also been started long ago. In abat to-3 BC, the ancient Greek philosopher Theophrastus explains that vinegar reacts with metals to form various dyes, such as white lead (lead carbonate) and verdigris, which is a green substance mixture of salts containing copper and copper ( II) acetate. The Romans produced sapa, a very sweet syrup, by boiling the wine is sour. Sapa contain lead acetate, a sweet substance also called sugar of lead and sugar of Saturn. Finally, it continues to poisoning with lead by Roman officials.
In the 8th century, Persian scientist Jabir ibn Hayyan produce concentrated acetic acid from vinegar through distillation. During the Renaissance, glacial acetic acid produced from the dry distillation of metal acetates. In the 16th century German alchemist Andreas Libavius ​​explain the procedure, and compared the glacial acetic acid produced the vinegar. Apparently glacial acetic acid has many different properties with a solution of acetic acid in water, and many experts believe that chemicals were two different substances. French chemist Pierre athlete finally prove that the two substances are essentially the same.
In 1847 the German chemist Hermann Kolbe synthesized acetic acid from inorganic substances for the first time. Chemical reactions do is chlorination of carbon disulfide to carbon tetrachloride, followed by pyrolysis into tetrakloroetilena and chlorination to trichloroacetic acid in water, and finally through the electrolytic reduction to acetic acid.
Since 1910 most of the acetic acid produced from piroligneous liquid obtained from the distillation of wood. These fluids reacted with calcium hydroxide producing calcium acetate and then acidified with sulfuric acid produces acetic acid.


Frozen crystals of acetic acid
Chemical properties
Acidity
Hydrogen atoms (H) in the carboxyl group (-COOH) in carboxylic acids such as acetic acid can be released as H + ions (protons), thus giving the acid. Acetic acid is a weak monoprotic acid with a value of pKa = 4.8. Conjugate base is acetate (CH3COO-). A 1.0 M solution of acetic acid (approximately equal to the concentration in the vinegar) has a pH of approximately 2.4.

Cyclic dimer
The crystal structure of acetic acid shows that acetic acid molecules form a dimer pairs are linked by hydrogen bonds. Dimers can also be detected in the steam temperature of 120 ° C. Dimers also occur in an aqueous solution in a solvent non-hydrogen-bonded, and sometimes on pure acetic acid. Dimer tampered with the solvent hydrogen bond (eg water). Dimer dissociation enthalpy is estimated 65.0-66.0 kJ / mol, the entropy of dissociation of about 154-157 J mol-1 K-1. [5] The nature of dimerization is also shared by other simple carboxylic acids.
As the solvent
Acetic acid solvent protic liquid is hydrophilic (polar), much like water and ethanol. Acetic acid has a dielectric constant of the medium is 6.2, so that it can dissolve both polar compounds and inorganic salts are like sugar and non-polar compounds such as oils and elements such as sulfur and iodine. Acetic acid bercambur easily with polar or nonpolar solvents such as water, chloroform and hexane. Solubility properties and ease of mixing of acetic acid makes it widely used in the chemical industry.
Chemical reactions
Acetic acid is corrosive to many metals such as iron, magnesium, and zinc, forming hydrogen gas and acetate salts (called metal acetate). Metal acetates can also be obtained by reaction of acetic acid with a suitable base. Famous example is the reaction of baking soda (sodium bicarbonate) reacts with vinegar. Hapir all acetate salts dissolve well in water. One exception is chromium (II) acetate. Examples acetate salt formation reactions:
Mg (s) + 2 CH3COOH (aq) → (CH3COO) 2mg (aq) + H2 (g)
NaHCO3 (s) + CH3COOH (aq) → CH3COONa (aq) + CO2 (g) + H2O (l)
Aluminum is a metal that is resistant to corrosion because it forms a layer that protects the aluminum oxide surface. Therefore, acetic acid usually transported with aluminum tanks.
Acetic acid undergo reactions of carboxylic acids, such as acetic acid to produce a salt when react with alkali, producing metal ethanoate when reacting with metals, and produce metal ethanoate, water and carbon dioxide when it reacts with carbonate or bicarbonate salt. The most well-known organic reactions of acetic acid is the formation of ethanol by reduction, the formation of carboxylic acid derivatives such as acetyl chloride or acetic anhydride via nucleophilic substitution. Acetic anhydride is formed through condensation two molecules of acetic acid. Esters of acetic acid can be obtained via Fischer esterification, and also the formation of amides. At a temperature of 440 ° C, acetic acid decomposes into methane and carbon dioxide, or ketene and water.
Detection
Acetic acid can be identified by a distinctive smell. In addition, salts of acetic acid reacts with a solution of iron (III) chloride, which produces a solid red color is lost when the solution is acidified. Acetate salts when heated with arsenic trioxide (AsO3) form kakodil oxide (AsO3) form kakodil oxide ((CH3) 2AS-O-As (CH3) 2), which is easily recognizable with an unpleasant smell.
Acetic acid is produced synthetically or naturally through bacterial fermentation. Now only 10% of the production of acetic acid produced through the natural path, but most of the laws governing the acetic acid found in vinegar should come from biological processes. Of acetic acid produced by the chemical industry, 75% of which is produced by methanol carbonylation. The rest is generated through alternative methods.
Total world production of acetic acid was estimated at 5 Mt / a (million tonnes per year), half of which is produced in the United States. Europe produces about 1 Mt / a and continued to decline, while Japan produced about 0.7 Mt / a. 1:51 Mt / a is produced through recycling, so the total market acetic acid reaches Mt 6:51 / a.Perusahan largest producer of acetic acid are Celanese and BP Chemicals. Other manufacturers are Millennium Chemicals, Sterling Chemicals, Samsung, Eastman, and Svensk Etanolkemi.
Acetic Acid Biosynthesis
Acetic acid is a product of the catabolism of aerobic glycolysis pathway or glucose reshuffle. Pyruvic acid as a product of oxidation of glucose oxidized by NAD + terion then immediately bound by Coenzyme-A. In prokaryotes, this process occurs in the cytoplasm while in eukaryotes takes place in the mitochondria.

Production
1. Carbonylation of methanol
Most pure acetic acid produced by carbonylation. In this reaction, methanol and carbon monoxide react to produce acetic acid
CH3OH + CO → CH3COOH

The process involves iodomethane as an intermediate, in which the reaction itself occurs in three stages with metal complex catalysts in the second stage.
(1) CH3OH + HI → CH3I + H2O
(2) CH3I + CO → CH3COI
(3) CH3COI + H2O → CH3COOH + HI

If the above reaction conditions arranged in such a way, the process can also be produced as a by-product of acetic anhydride. Methanol carbonylation long been the most promising methods in the production of acetic acid because both methanol and carbon monoxide are commodity raw materials. Henry Dreyfus developing embryo carbonylation of methanol plant at the company Celanese in 1925. [9] However, the lack of practical materials that can be filled with corrosive materials from the reaction at the required pressure of 200 atm cause the method was abandoned for commercial purposes. It was not until 1963 that the first commercial plant using methanol carbonylation was founded by German chemical company, BASF catalysts cobalt (Co). In 1968, it was discovered Rhodium catalyst complexes, cis-[Rh (CO) 2I2] - which can operate optimally at low pressure without byproducts. The first plant using the catalyst was the U.S. chemical company Monsanto in 1970, and Rhodium berkatalis methanol carbonylation method called Monsanto process and a method of production of acetic acid the most dominant. At the end 1990'an, British Petroleum petrochemical companies commercialize Cativa catalyst ([Ir (CO) 2I2] -) which is supported by the ruthenium. Iridium-based process is more efficient and more "green" than the previous method [10], so in lieu of Monsanto.

2. Oxidation of acetaldehyde
Prior to the commercialization of Monsanto process, most acetic acid produced by oxidation of acetaldehyde. Now the oxidation of acetaldehyde is a method of acetic acid production the second most important, though not competitive when compared to the carbonylation of methanol. Acetaldehyde is produced through the oxidation used butane or light naphtha, or the hydration of ethylene. When butene or light naphtha is heated with air along with several metal ions, including manganese ions, cobalt and chromium, peroxides are formed which then decomposes to acetic acid according to the equation below.
2 C4H10 + 5 O2 → 4 CH3COOH + 2 H2O

Generally, the reaction is run at a temperature and pressure such that the temperature reached as high as possible namut still liquid butane. Reaction conditions are generally about 150 ° C and 55 atm. Byproducts such as butanone, ethyl acetate, formic acid and propionic acid may also be formed. Products also commercially valuable, and if desired reaction conditions can be modified to produce more by-products, but the separation of acetic acid as an obstacle to cost more.

Through the same conditions and catalyst of acetaldehyde can be oxidized by oxygen in the air produces acetic acid.
2 CH3CHO + O2 → 2 CH3COOH

Using modern catalysts, this reaction can have a yield ratio (yield) is greater than 95%. The main byproducts are ethyl acetate, formic acid and formaldehyde, all of which have lower boiling points than acetic acid so that it can be separated easily by distilas

Use
Acetic acid is used as a chemical reagent to produce a variety of chemical compounds. The majority (40-45%) of acetic acid is used as a material world for the production of vinyl acetate monomer (vinyl acetate monomer, VAM). Addition of acetic acid is also used in the production of acetic anhydride and ester. The use of acetic acid, including the use of the relatively small vinegar.