Propanoic acid, 288 Table

The barriers to rotation about the N-C bond have been determined b dynamic nuclear magnetic resonance for A -isopropyl (80. 81). propanoic acid (74). A -ethyl (82). N-benzyl. and A -neopentyl substituents (82). Selected values of these barriers are given in Tables VII-6 and VII-7. 

Experimental pKa data suggests that simple alkyl groups all affeet acid-base reactivity in roughly the same way. What is more, this universal alkyl effect is roughly equivalent to the effect of a hydrogen atom. For example, the difference in pKa between water and ethanol is approximately the same as that between formic acid and propanoic acid (see table at right). 

Step 1 Write the equation for the dissociation equilibrium of propanoic acid in water. Then set up an ICE table. 

Food preservatives prevent spoilage of food due to microbial growth. The most commonly used preservatives include table salt, sugar, vegetable oils and sodium benzoate, CeHgCOONa. Sodium benzoate is used in limited quantities and is metabolised in the body. Salts of sorbic acid and propanoic acid are also used as preservatives. 

Enolate dianions from 3-benzoyl-2-fc-rt-butylT-methyl-5-oxo-4-imidazolidineacetic and -propanoic acids 4, obtained from aspartic and glutamic acid, have also been used in diastcreose-lective alkylation reactions (see Table 4)7. 

In the first of these reactions (Equation 11-2), a hydrocarbon is produced by the cleavage of a borane, R3B, with aqueous acid, or better, with anhydrous propanoic acid, CH3CH2C02H. The overall sequence of hydroboration-acid hydrolysis achieves the reduction of a carbon-carbon multiple bond without using hydrogen and a metal catalyst or diimide (Table 11-3) ... 

The condensation of a carboxylic acid with ammonia or an amine yields an amide. The amide in Table 15-1 resulted from the condensation of propanoic acid with ammonia. The example in the preceding section involved the condensation of acetic acid with a primary amine. A very important class of biochemical molecules are the amino acids, which join to form protein molecules by the condensation of the amine group of one molecule to the acid group of the next. The amide linkage in this case has the special name peptide. 

Table 4.5 Examples of the different electronic substitution constants used in QSAR studies. Inductive substituent constants (crO are the contribution the inductive effect makes to Hammett constants and can be used for aliphatic compounds. Taft substitution constants (cr ) refer to aliphatic substituents but use propanoic acid (the 2-methyl derivative of ethanoic acid) as the reference point. The Swain-Lupton constants represent the contributions due to the inductive (.F) and mesomeric or resonance (R) components of Hammett constants. Adapted from An Introduction to the Principles of Drug Design and Action by Smith and Williams 3rd Ed. (1998) Ed. H.J.Smith. Reproduced by permission of Harwood Academic Publishers.

A mmetric hydrogenation catalyzed by palladium deposited on simpler synthetic polypeptides, homopolymers of a-amino acids or their derivatives, was studied by Beamer, Belding and Pickling (5, (5). In the hydrogenation in ethanol of a-meth-ylcinnamic acid [ J] and of a-acetamidocinnamic acid [4] to give 2-methyl-3-phenyl-propanoic acid [5] and phenylalanine, respectively, the predominant optical antipodte was found much dependent on the secondary conformation of the polypeptide (Table 1). 

Similar rules apply for compounds 10-13, which contain rings. Compounds 10 and 11 are isomeric keto nitriles, and both must be named as nitriles according to Table A.2. Substance 10 is named as a benzonitri e since the -CN functional group is a substituent on the aromatic ring, but substance 11 is named as an acetonitrile since the -CN functional group is part of an open chain. The correct names are 2-acety -4-methylbenzonitrile (10) and (2-acetyl-4-methylphenyl)acetonitrile (11). Compounds 12 and 13 are both keto acids and must be named as acids. The correct names are 3-(2-oxocyclohexyl)propanoic acid (12) and 2- 3-oxopropyl)cyclohexane carboxylic acid (13). 

Table 9.3 Experimental Results for Cell (9.5.12) for the Case of Propanoic Acid at 25°C...

Fig. 9.4 Plot of the function on the left-hand side of equation (9.5.16) against ionic strength I using the data in table 9.3. Extrapolation of the straight line fitted by least squares to / = 0 allows one to estimate the acidity constant for propanoic acid.

The following table brings together data for propanoic acid and butanoic acid and the results, for 25°C, obtained in Worked Problems 8.5 to 8.7. Comment on and interpret these results. 

Anisole can be acylated with carboxylic acids over ZSM-5 catalyst. The reaction is carried out in a batch reactor under reflux for 2 d. Table 4.12 shows fhe resulfs obfained utilizing carboxylic acids with different chain length. Prom propanoic acid to stearic acid, the conversion decreases from 92% to 1%, showing a trend opposite to that observed with REY zeolites. This behavior can be ascribed to the small micropore size of ZSM-5, in which the formation of large molecules is difficulf (for penfanoic to octanoic acid) or impossible (for longer-chain carboxylic acids). The poor conversion of AAC can be affribufable to the low reflux temperature. 

The formic, acetic, and propanoic acids listed as major MSS vapor-phase components were defined as ciliastats by Wynder et al. (4304, 4350) in the mid-1960s [see summary graph, p. 254, Table VII-31 in (4332)]. However, Wynder and Hoffmann (4332) were among the first to comment on the fact that all vapor-phase ciliastats are water soluble and therefore may be removed from the smoke stream by solution in the fluids coating the oral cavity. In their 1967 book [see p. 646 in (4332)], they stated ... 

New linoleums are often odorous materials because of emitted hexanal, propanoic acid and nonanal (Jensen et al., 1995), but emissions from linoleums in use for several years still cause odor problems. The emissions of linoleums in chemical terms are given in Table 3.2-6. It seems, as expected, that the main emissions of both new and used linoleums contain volatile substances which are similar in new and used products, degradation reactions occur in the material during use, and some emissions are common for both new and old materials. 

The calculations performed for acetic and propanoic acids (see Table 8) confirm the opportunity to use the medium-sized TZVP basis set to obtain good results. On the other hand the lack of other theoretical data regarding the propanoic acid reflects the difficulty to treat, with expensive procedures, such a kind of system. 

However, not all alcohols can be oxidized to aldehydes and, subsequently, carboxylic acids. To understand why, compare the oxidations of 1-propanol and 2-propanol, shown in Table 22.13. Note that oxidizing 2-propanol yields a ketone, not an aldehyde. Unlike aldehydes, ketones resist further oxidation to carboxylic acids. Thus, while the pro-panal formed by oxidizing 1 -propanol easily oxidizes to form propanoic acid, the 2-propanone formed by oxidizing 2-propanol does not react to form a carboxylic acid. 

Volatile fatty acids p resent in wine may derive from the anabolism of lipids, resulting in compounds with even number of carbon atoms, by oxidative decarboxylation of a-keto acids or by the oxidation of aldehydes. Volatile fatty acids synthesised from a-keto acids are mainly propanoic add, 2-methyl-l-propanoic acid (isobutyric acid), 2-methyl-l-butanoic acid, 3-methyl-l-butanoic acid (isovaleric acid 3-methylbutyric add) and phenylacetic add. From lipid metabolism, the following fatty acids are reported butanoic add (butyric), hexanoic acid (caproic), odanoic acid (caprylic) and decanoic add (capric) (Dubois, 1994). Although fatty adds are charaderized by unpleasant notes (Table 1), only few compounds of this family attain its perception threshold. However, their flavour is essential to the aromatic equilibrium of wines (Etievant, 1991). 

Esters, amides, and acid hahdes are usually named as derivatives of the parent carboxylic acid. Thus, in Table 4.1, you find ethyl propanoate listed under the parent carboxylic acid, propanoic acid. If you have trouble finding a particular ester under the parent carboxylic acid, try looking under the alcohol part of the name. For example, isopentyl acetate is not listed under acetic acid, as expected, but instead is foimd under the alcohol part of the name (see Table 4.1). Fortunately, this handbook has a Synonym Index that nicely locates isopentyl acetate for you in the main part of the handbook. 

Acid anhydrides have structure 58 and are named by recognizing that the structure consists of two carboxylic acid units. The lUPAC rules demand that the two acids be named sequentially, followed by the word anhydride. For anhydride 63 in Table 16.3, one component is derived from butanoic acid and the other from propanoic acid. The names of the acid are listed alphabetically, so the name of 63 is butanoicpropanoic anhydride. For a general rule of naming, list R and R in 63 alphabetically, followed by the word anhydride). Anhydride 63 is an unsymmetrical anhydride because the two acid components are different. If both acid components are identical, it is a symmetrical anhydride such as 64. Using both acid names for this compound leads to diethanoic anhydride, or simply ethanoic anhydride When the single name is used, the anhydride is understood to be symmetrical. Anhydride 64 is derived from ethanoic acid, which has the common name acetic acid, so the common name acetic anhydride is often used for 65. 

The nomenclature for carboxylic acids follows the familiar pattern of adding the functional group name -oic acid to the named hydrocarbon chain except that the common names formic acid and acetic acid are still widely accepted. Thus, formic acid is methanoic acid, acetic acid is ethanoic acid, propionic acid is propanoic acid, and -butyric acid is butanoic acid. The CAS numbers (Chemical Abstract Service, American Chemical Society) for the carboxylic acids are listed in Table 6.1 along with the physical properties. The CAS numbers refer to the major carboxylic acid component. Refer to the Material Safety Data Sheet (MSDS) for CAS numbers of any minor impurities in the solvent. 

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