Physical Properties of Acids

All three are important commercial chemicals, used to make polymers and other useful materials. 

Finally, it is useful to have a name for an acyl group. Particular acyl groups are named from the corresponding acid by changing the -ic ending to -yl. 

The first members of the carboxylic acid series are colorless liquids with sharp or unpleasant odors. Acetic acid, which constitutes about 4% to 5% of vinegar, provides the characteristic odor and flavor. Butyric acid gives rancid butter its disagreeable odor, and the goat acids (caproic, caprylic, and capric in Table 10.1) smell like goats. 3-Methyl-2-hexenoic acid, produced by bacteria, is responsible for the offensive odor of human armpits. Table 10.3 lists some physical properties of selected carboxylic acids. 

Carboxylic acids are polar. Like alcohols, they form hydrogen bonds with themselves or with other molecules (Sec. 7.4). Therefore, they have high boiling points for their molecular weights—higher even than those of comparable alcohols. For example, acetic acid and propyl alcohol, which have the same formula weights (60 g/mol), boil at 118°C and 97°C, respectively. Carboxylic acids form dimers, with 

Hydrogen bonding also explains the water solubility of the lower molecular weight carboxylic acids. 

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Students will identify the whiting compounds prepared as acidic or basic and research the chemical and physical properties of acids and bases. 

Regarding the physical properties of acids, they taste sour and leave a burning sensation on one s skin. Chemically, they are corrosive and lose their physical properties when in contact with basic solutions. In solution, they produce an excess of hydrogen or hydronium ions. Regarding physical properties of bases, they taste bitter and feel slippery. Chemically, they react with acids to form salts and water. In solution, they produce an excess of hydroxide ion. The whiting compounds produce excess hydroxide ions in solution. 

Describe the trends in physical properties of acid derivatives, and compare the relative reactivity of esters, thioesters, amides, nitriles, anhydrides, and acid chlorides. 

In this section we will examine the effect that hydrocarbons, specifically methane, have on the physical properties of acid gases. The effect on the vapor pressure (i.e., the vapor-liquid equilibrium) will be discussed in a subsequent chapter. 

In the preceding chapters, details were presented for estimating the physical properties of acid gas, and procedures were presented for designing the equipment required. Note that in this section some of the conversions are not exact because of the approximate nature of the information presented. Although some of the rules of thumb presented in this section are general in nature, the reader is wise to apply them only to acid gas systems. 

Lucey, J.A., and Singh, H. (1997) Formation and physical properties of acid milk gels a review. Food Res. Ini. 30, 529 542. 

Electrical conductivity Another physical property of acid and base solutions is the ability to conduct electricity. Pure water is a nonconductor of electricity, but the addition of an acid or base produces ions that cause the resulting solution to become a conductor. 

Allara D L and Nuzzo R G 1985 Spontaneously organized molecular assemblies. 1. Formation, dynamics, and physical-properties of normal-alkanoic acids adsorbed from solution on an oxidized aluminum surface Langmuir 1 45-52... 

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

The physical properties of a number of aliphatic acid chlorides are collected in Table 111,88. 

The physical properties of a few tjrpical acid chlorides of aromatic acids are collected in Table IV, 18 7). Some acid anhydrides are also included in this Table (compare Section 111,94). 

Specific rotation is a physical property of a substance just as melting point boil mg point density and solubility are For example the lactic acid obtained from milk is exclusively a single enantiomer We cite its specific rotation m the form [a]o =+3 8° The temperature m degrees Celsius and the wavelength of light at which the measure ment was made are indicated as superscripts and subscripts respectively... 

The physical properties of a typical amino acid such as glycine suggest that it is a very polar substance much more polar than would be expected on the basis of its formula tion as H2NCH2CO2H Glycine is a crystalline solid it does not melt but on being heated It eventually decomposes at 233°C It is very soluble m water but practically insoluble m nonpolar organic solvents These properties are attributed to the fact that the stable form of glycine is a zwittenon, or inner salt... 

TABLE E Selected Physical Properties of Representative Carboxylic Acids and Dicarboxylic Acids... 

Equivalent Weights Acid-base titrations can be used to characterize the chemical and physical properties of matter. One simple example is the determination of the equivalent weighf of acids and bases. In this method, an accurately weighed sample of a pure acid or base is titrated to a well-defined equivalence point using a mono-protic strong acid or strong base. If we assume that the titration involves the transfer of n protons, then the moles of titrant needed to reach the equivalence point is given as... 

Peptides and proteins are formed by linking successive amino acids into chains or rings. The order (sequence) and types of amino acids determine the chemical and physical properties of peptides and proteins. 

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

Table 11. Some Physical Properties of Cyanoacetic Acid and Methyl and Ethyl Esters ...

Some of the physical properties of fatty acid nitriles are Hsted in Table 14 (see also Carboxylic acids). Eatty acid nitriles are produced as intermediates for a large variety of amines and amides. Estimated U.S. production capacity (1980) was >140, 000 t/yr. Eatty acid nitriles are produced from the corresponding acids by a catalytic reaction with ammonia in the Hquid phase. They have Httie use other than as intermediates but could have some utility as surfactants (qv), mst inhibitors, and plastici2ers (qv). 

Table 14. Some Physical Properties of Fatty Acid Nitriles...

A summary of the physical properties of glacial acetic acid is given in Table 5. ... 

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