Natural sources, acetic acid

Colligative properties can be sources of insight into not only the properties of solutions, but also the properties of the solute. For example, acetic acid, CH.COOH, behaves differently in two different solvents, (a) The freezing point of a 5.00% by mass aqueous acetic acid solution is — l.72°C. What is the molar mass of the solute Explain any discrepancy between the experimental and the expected molar mass, (b) The freezing-point depression associated with a 5.00% by mass solution of acetic acid in benzene is 2.32°C. Whar is the experimental molar mass of the solute in benzene What can you conclude about the nature of acetic acid in benzene ... 

Because of their abundance in nature, carboxylic acids were among the first organic compounds studied in detail. No systematic nomenclature system was then available, so the acids were usually named after some familiar source. Acetic acid,... 

Using What Nature Provided - Acetic Acid from Natural Sources. 

Many carboxylic acids have common names that are derived from Latin or Greek words that indicate one of their natural sources. Methanoic acid is called formic acid formica, Latin ant). Ethanoic acid is called acetic acid acetum, Latin vinegar). Butanoic acid is one compound responsible for the odor of rancid butter, so its common name is butyric acid butyrum, Latin butter). Pentanoic acid, as a result of its occurrence in valerian, a perennial herb, is named valeric acid. Hexanoic acid is one compound associated with the odor of goats, hence its common name, caproic acid caper, Latin goat). Octadecanoic acid takes its common name, stearic acid, from the Greek word stear, for tallow. 

A carboxylic acid contains a carboxyl group, which is a hydroxyl group attached to a carbonyl group. Many carboxylic acids have common names, which are derived from their natural sources. Formic acid is injected under the skin from bee or red ant slings and other insect bites. Acetic acid is produced when ethanol in wines and apple cider reacts with the oxygen in the air. Propionic acid is obtained from the fats in dairy products. Butyric acid gives the foul odor to rancid butter (see Table 14.2). 

Vapors emitted from the materials of closed storage and exhibit cases have been a frequent source of pollution problems. Oak wood, which in the past was often used for the constmction of such cases, emits a significant amount of organic acid vapors, including formic and acetic acids, which have caused corrosion of metal objects, as well as shell and mineral specimens in natural history collections. Plywood and particle board, especially those with a urea—formaldehyde adhesive, similarly often emit appreciable amounts of corrosive vapors. Sealing of these materials has proven to be not sufficiently rehable to prevent the problem, and generally thek use for these purposes is not considered acceptable practice. 

Carboxylic acids having 6—24 carbon atoms are commonly known as fatty acids. Shorter-chain acids, such as formic, acetic, and propionic acid, are not classified as fatty acids and are produced synthetically from petroleum sources (see Acetic acid Formic acid and derivatives Oxo process). Fatty acids are produced primarily from natural fats and oils through a series of unit operations. Clay bleaching and acid washing are sometimes also included with the above operations in the manufacture of fatty acids for the removal of impurities prior to subsequent processing. 

Acetic acid (qv) can be produced synthetically (methanol carbonylation, acetaldehyde oxidation, butane/naphtha oxidation) or from natural sources (5). Oxygen is added to propylene to make acrolein, which is further oxidized to acryHc acid (see Acrylic acid and derivatives). An alternative method adds carbon monoxide and/or water to acetylene (6). Benzoic acid (qv) is made by oxidizing toluene in the presence of a cobalt catalyst (7). 

This chapter lists some representative examples of biochemicals and their origins, a brief indication of key techniques used in their purification, and literature references where further details may be found. Simpler low molecular weight compounds, particularly those that may have been prepared by chemical syntheses, e.g. acetic acid, glycine, will be found in Chapter 4. Only a small number of enzymes and proteins are included because of space limitations. The purification of some of the ones that have been included has been described only briefly. The reader is referred to comprehensive texts such as the Methods Enzymol (Academic Press) series which currently runs to more than 344 volumes and The Enzymes (3rd Edn, Academic Press) which runs to 22 volumes for methods of preparation and purification of proteins and enzymes. Leading referenees on proteins will be found in Advances in Protein Chemistry (59 volumes. Academic Press) and on enzymes will be found in Advances in Enzymology (72 volumes, then became Advances in Enzymology and Related Area of Molecular Biology, J Wiley Sons). The Annual Review of Biochemistry (Annual Review Inc. Patio Alto California) also is an excellent source of key references to the up-to-date information on known and new natural compounds, from small molecules, e.g. enzyme cofactors to proteins and nucleic acids. 

Many carboxylic acids were first isolated from natural sources and were given names based on their origin. Fonnic acid (Latin formica, meaning ant ) was obtained by distilling ants. Since ancient times acetic acid (Latin acetum, for vinegar ) has been known to be present in wine that has turned sour. Butyric acid (Latin butyrum, meaning butter ) contributes to the odor of both rancid butter and ginkgo benies, and lactic acid (Latin lac, for milk ) has been isolated from sour milk. 

In more detail the nutrient medium used may contain sources of carbon such as starch, hydrolyzed starch, sugars such as lactose, maltose, dextrose, sucrose, or sugar sources such as molasses alcohols, such as glycerol and mannitol organic acids, such as citric acid and acetic acid and various natural products which may contain other nutrient materials in addition to carbonaceous substances. 

A solution of acetic acid formed in this manner is familiar as vinegar. Acids are also obtained from natural sources. A few examples are listed in Table 21-7. 

Since carboxylic acids are amongst the earliest organic compounds to be isolated from nature, a large number of them are known by their common names. The common names end with the suffix -ic acid and have been derived from Latin or Greek names of their natural sources. For example, formic acid (HCOOH) was first obtained from red ants (Latin formica means ant), acetic acid (CH C OOH) from vinegar (Latin acetum, means vinegar), but n ic acid (CH3CH2CH2COOH) from rancid butter (Latin butyrum, means butter). 

For Reaction 4 to proceed selectively it will be necessary that Reaction 5c proceeds faster than, or concertedly with. Reactions 5a, b so that no substantial build-up of EDA can take place and hence Reaction 6 will be prevented. Thus, we interpret the exceptional behaviour of Znl2, CH3I, and HI as iodide promoters in the sense that they allow a high hydrogenolysis-hydrogenation activity of the Ru function in the catalyst system. Whereas the hydrocarbonylation function of Rh (Reactions 5a, b)is promoted by a variety of iodides, it appears that the hydrogenolysis function of Ru (Reaction 5c)is very sensitive to the nature of the iodide source used, as evidenced by a low ethyl acetate/acetic acid product ratio obtained with iodides such as AII3 and Lil. 

In short, while the focus has been primarily on sulfuric and nitric acids as a source of acid deposition, it is clear that organic acids can also contribute significantly. The gas-phase concentrations of the simplest carboxylic acids, formic acid and acetic acid, are relatively high even in remote regions, of the order of a ppb. Both natural and anthropogenic sources have been... 

Common names, such as formic (ant) and butyric (butter) acids, are based on the natural source of the acid. The positions of substituent groups are shown by Greek letters a, y, S, etc. Some have names derived from acetic acid, e.g., (CH,),CCOOH and C H,CH,COOH, are trimethylacetic acid and phenylacetic acid, respectively. Occasionally they are named as carboxylic acids, e.g. 

---