Aniline standard solution

The first attempts at predicting solubility were largely empirical. Paint technologists employed various approaches. In one approach kauri-butanol values were equal to the minimum volume of test solvent that produced turbidity when added to a standard solution of kauri-copal resin in 1-butanol. The aniline point is the lowest temperature where equal volumes of aniline and the test solvent are completely miscible. Both tests are measures of the relative aromaticity of the test solvent. 

For this purpose a standard solution containing 0-005 gram of furfural per litre of pure 50% alcohol is prepared, the spint to be tested being also brought to 50% concentration. 10 c c of each of the two liquids are treated at the same time with 10 drops of aniline and 1 c c of concentrated acetic acid. If, after 20 minutes, the colorations are approximately similar, they are compared in the Duboscq colorimeter, if, however, the two colorations differ greatly, the test is repeated m the manner described for the determination of the aldehydes (tee above). The proportion of furfuraldehyde present is readily calculated from the colorimeter readmgs... 

For each of the diluted Standard Solutions—1, 2, and 3— plot absorbance against p-nitroaniline mM concentration. The result is a straight line that passes through the origin. Calculate the millimolar extinction coefficient (e) of each Standard p-Nitro-aniline Solution using the following formula ... 

FIGURE 11.16 Electrophorogram for a standard solution of aromatic amines. Peaks 1, pyridine 2, /7-phenylenediamine 3, benzidine 4, o-toluidine 5, aniline 6, A/,A -dimethylaniline 7, p-anisidine 8, /7-chloroaniline 9, m-chloroaniline 10, ethylaniline 11, a-naphthylamine 12, diethyl-aniline 13, A -(l-naphthyl)ethylenediamine 14, 4-aminophenazone 15, o-chloroaniline 16, 3,4-dichloroani-line 17, 3,3 -dichlorobenzidine 18, 2-methyl-3-nitroaniline 19, 2,4-dichloroaniline 20, 2,3-dichloroaniline 21, 2,5-dichloroaniline. (From Cavallaro, A., Piangerelli, V., Nerini, F., Cavalli, S., and Reschiotto, C., J. Chromatogr., 709, 361-366, 1995.)... 

Also the paint industry, formerly the main end-user of solvents, attempted to produce a quantitative solvent power data system [5]. This related solvency to certain standard solutes, used in their industry. These could either be a well-known natural (Kauri-resin) or later a synthetic (nitrocellulose) paint binder. The result was the introduction of the Kauri-Butanol number, which applies to hydrocarbon solvents only and the NC-dilution ratio which is used for oxygenated solvents. Another test, used in conjunction with hydrocarbon solvents, is based on the fact that aniline is hardly miscible with aliphatic hydrocarbons but mixes very well with aromatics. The Kauri-Butanol (KB) number as defined in ASTM D 1133 is a measure of the tolerance of a standard solution of Kauri resin in -butanol to hydrocarbon diluent. Standard hydrocarbon solvents used to calibrate the Kauri solution are toluene (KB-number 105) and a 75% v -heptane/25% v toluene blend (KB-number 40). The KB-value increases from approx. 20 to over 100 in the order ... 

Solvents. Perhaps the single most important property of a solvent is its ability to dissolve various resins, gum-like materials, oils, nitrocellulose lacquers, etc., and accordingly there are numerous solvency tests of which the aniline point and kauri butanol number are the best known. The kauri butanol number consists of ascertaining the volume of sample that will cause a standard solution of kauri gum in butyl alcohol to become so opaque that 10-point type is illegible when viewed through the solution. Similar tests employ nitrocellulose and butyl or ethyl acetate solvents. 

Dir ect nitration of aniline and other ar ylanines fails because oxidation leads to the formation of dark-colored tars. As a solution to this problem it is standard practice to first protect the amino group by acylation with either acetyl chloride or acetic anhydride. 

Historically the first fully unsaturated azepine was obtained by Wolff in 1912 by the decomposition of phenyl azide in aniline. However, the actual structure of this product, named dibenzamil , remained unknown until 1955, when Huisgen and coworkers showed it to be an anilinoazepine, originally formulated as the 7-anilino-2H-azepine, but later corrected, mainly on the basis of HNMR evidence, to the 2-anilino 3H-tautomer (221 R1=PhNH R2 = H). Subsequently, the thermolysis and photolysis of aryl azides in primary, secondary and, in certain instances, tertiary amine solution has become a standard method for the preparation of 2-amino-3/f-azepines (79AG(E)900,8lAHC(28)23l). 

Colorimetric Methods are used only for the estimation of very small percentages of vanadium, e.g. in vanadium steels and alloys. The most important depend on the intensity of the reddish-brown colour produced by the action of hydrogen peroxide on an acid vanadate solution.3 If chromium is present, an equal amount must be introduced into the standard vanadium solution under the same conditions of temperature, acid concentration, etc. Phosphoric acid is added to destroy any yellow colour due to ferric iron, and either hydrofluoric acid or ammonium fluoride to destroy any colour produced by titanium.4 A colorimetric method for the simultaneous estimation of small quantities of titanium and vanadium has also been worked out.5 Other colorimetric processes are based on (a) the formation of a yellow to black coloration, due to aniline black, in the presence of aniline hydrochloride and potassium chlorate or other oxidising agent,6 and (b) the orange coloration finally produced when an acid solution of a vanadate is brought into contact with strychnine sulphate.7... 

After the sulfanilic acid and nitrite solutions have been standardized, 1 N aniline solution is prepared. Pure aniline (200 cc.) is distilled from a small distillation flask (Fig. 7, page 71) at such a rate that the distillation is complete in 45 minutes. The aniline which comes over within a range of one-half degree between 184 and 185°C. is used for preparing the solution. The specific gravity should bie 1.0260 to 1.0265 at 17.5°. 

According to the Brpnsted definition, the acidity of a molecule is associated with its capacity to give up a proton Ph—NH2 — Ph—NH +H+. The change of standard enthalpy or free energy of this deprotonation reaction is a measure of the intrinsic acidity. As discussed above, in solution, the propensity of an aniline derivative is to accept a proton. The measured dissociation constant (pATa) is related to the basicity of the neutral molecule (or the acidity of the anilinium cations). As a consequence, relatively little is known about their acidity and/or the anilinide anions. However, the NH acidities have been well established in hydroxamic acids even though the latter usually behave as O-acids134. It is therefore of interest to get some insight into the deprotonation of aniline in the gas phase. 

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