Aliphatic carboxylic acids, 288 Table

I he present procedure, a modification of one reported earlier by ilie submitters," has been applied to the a-chlorination of a scries of aliphatic carboxylic acids (Table I). In these reactions... 

A very interesting steric effect is shown by the data in Table 7-12 on the rate of acid-catalyzed esterification of aliphatic carboxylic acids. The dissociation constants of these acids are all of the order 1(T, the small variations presumably being caused by minor differences in polar effects. The variations in esterification rates for these acids are quite large, however, so that polar effects are not responsible. Steric effects are, therefore, implicated indeed, this argument and these data were used to obtain the Es steric constants. Newman has drawn attention to the conformational role of the acyl group in limiting access to the carboxyl carbon. He represents maximum steric hindrance to attack as arising from a coiled conformation, shown for M-butyric acid in 5. 

For a wide variety of aliphatic carboxylic acids, including some with aromatic substituents, the product yields for CO and C02 are in an approximately constant ratio of 1 10 for radiolysis at 298 K. Values for some typical compounds are given below in Table II. 

Since decarboxylation is a primary reaction of the aliphatic carboxylic acids, it is interesting to compare the radical yield measured at 77 K (3) with the yield of carbon monoxide plus carbon dioxide. These values are compared in Table III. The results suggest that there is a correlation between the loss of the carboxyl group and the formation of radicals in the carboxylic acids. 

A similar behaviour has been found to occur with the other N-acetyl amino acids. In each case, the most stable radical observed at 303 K was the alpha carbon radical, as was also observed for the aliphatic carboxylic acids. In Table VI the radical yields observed following gamma radiolysis of a series of N-acetyl amino acids at 303 K are reported, together with the stable radical intermediates observed at this temperature (5). 

The table lists the full series of aliphatic carboxylic acids that are found in plants and animals. In higher plants and animals, unbranched, longchain fatty acids with either 16 or 18 carbon atoms are the most common— e.g., palmitic and stearic acid. The number of carbon atoms in the longer, natural fatty acids is always even. This is because they are biosynthesized from C2 building blocks (see p.168). 

The protonation of aliphatic carboxylic acids can be followed by nmr techniques (as explained above) or spectrophotometrically, using a band near 190 nm in the ultraviolet. Some values are given in Table 3. The aliphatic... 

TABLE 12.6 Antifungal activity of aliphatic carboxylic acid salts... 

Several aliphatic carboxylic acids have been known for centuries, and their common names reflect their historical sources. Formic acid was extracted from ants formica in Latin. Acetic acid was isolated from vinegar, called acetum ( sour ) in Latin. Propionic acid was considered to be the first fatty acid, and the name is derived from the Greek protos pion ( first fat ). Butyric acid results from the oxidation of butyraldehyde, the principal flavor of butter butyrum in Latin. Caproic, caprylic, and capric acids are found in the skin secrehons of goats caper in Lahn. The names and physical properties of some carboxylic acids are listed in Table 20-1. 

Table 5 shows the partition coefficient of some common aliphatic carboxylic acids produced from fermentation.32 Aromatic carboxylic acids are not produced from fermentation because they are rarely formed by microorganisms. One noteworthy exception is the production of salicylic acid formed by Pseudomonas aeruginosa from naphthalene through biotransformation.1 The extraction of salicylic acid with and without amine in xylene was reviewed by Schiigerl1 in detail including equipment and operational parameters. 

An even simpler route to the fused-ring 1,3-dithiolium salts is by condensation of 203 with aromatic and even aliphatic carboxylic acids.131,13 > 137 The reaction, which is generally carried out in phosphorus oxychloride, proceeds rapidly and always in good yield. The parent member of this series of benzo-l,3-dithiolium salts is obtained in 80-90% yield when the acid used is formic acid (Table... 

The pyrolysis oil collected between 200 to 275 C in the second step was 18.14 % by wt. on an anhydrous wood basis and corresponded to the hemicelluloses degradation . In general, hemicelluloses decompose to yield furans and its derivatives as well as a series of aliphatic carboxylic acids. Hardwoods are composed of pentosan-based hemicelluloses, while hexosan-based hemicelluloses are found in softwoods. Hardwood produces more low molecular weight carboxylic acids and furans than softwood upon decomposition . In contrast, hardwood contains a lower quantity of fatty acids than softwood. Cl - C6 carboxylic acids, fatty acids (e.g. Cia), fiiran and derivatives were identified in this fraction. In the second pyrolysis step, a little rearrangement of the lignin polymer occurred which was based on the formation of small amount of phenolic compounds 0,395 % by wt., anhydrous wood basis). The main components of this fraction are listed in Table 2. Betulin and lupeol were abundant in this fraction. Furthermore, levoglucosan which has been reported earlier as a major compound in the cellulose-derived pyrolysis oils, was identified in the second... 

The aliphatic carboxylic acids have been known for a long time, and as a result have common names that refer to their sources rather than to their chemical structures. The common names of the more important acids are shown in Table 18.1. Formic acid, for example, adds the sting to the bite of an ant (Latin formicQy ant) butyric acid gives rancid butter its typical smell (Latin butyrum, butter) ... 

Table 4-4. pH Dependence of the retention of various aliphatic carboxylic acids on IonPac ICE-ASS. 

Table 1. UOz Complexes with monobasic aliphatic carboxylic acids...

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