Neutral equivalent

Product Neutral equivalent Color, Water, wt %, Melting point, °C, min Amine assay, %... 

To analy2e fatty amines, both wet and instmmental methods of analysis are used. Wet methods routinely used are total amine value (ASTM Method D2073) combining weight or neutralization equivalent primary, secondary, and tertiary amine content (ASTM Method D2083) moisture, Kad-Fischer (ASTM Method D2072) and iodine value, measure of unsaturation (ASTM Method D2075). These provide important information on physical and chemical characteristics of the amine products used in various appHcation areas (8,76,81). In addition to the ASTM methods available, the American Oil Chemists Society has developed methods of analysis for fatty amines (82). 

A purified fatty acid is recommended for the preparation of a pure a-sulfo acid. Purified palmitic acid (m.p. 60.8-61.4°, neutralization equivalent 256.2) is prepared by twice recrystallizing a good commercial grade of palmitic acid from acetone at 0°, using a solvent ratio of 10 ml. to 1 g. However, the reaction may be applied to commercial saturated higher fatty acids, if the iodine number is sufficiently low. The checkers obtained similar results with recrystaUized Neo-Fat 1-56 (Armour and Company, Chicago, 111.) or Eastman white label palmitic acid. 

The filtrate mentioned above, upon acidification thereof with HCI gave a darker acid which melted over a wide range, but had a neutral equivalent which also corresponds to that of (3-fluoranthoylpropionic acid. 

Very pure docosanedioic acid can be obtained by another recrystallization from about 450 ml. of 2-methoxyethanol. The recrystallized acid is collected on a Buchner funnel, and the well-pressed filter cake is suspended in 200 ml. of 95% ethanol, refiltered, and dried in air weight 112 g. (61%) m.p. 126-127° neutralization equivalent, 185-187. 

Equation 7.2 represents the rate law for quinone methide disappearance. This equation was derived using material balance where reactions occur from and equilibrating mixture of neutral and protonated quinone methide. Both the protonated (k2 process) and neutral equivalent (k2 and k4 processes) react to afford the observed major products shown in Scheme 7.18. Alternatively, the quinone methide can be protonated... 

The hydrolysis reaction is very slow at ambient temperatures and is accelerated by boiling chromium salt solutions (5). The hydrolysis reaction is characterized by the transformation of the deep blue colored CrtHgOJg to green colored hydrolyzed olates. Another indication is tnatan aged or boiled Cr(III) salt solution has a higher neutralization equivalent than a fresh one due to the hydrolytically produced protons. One way to establish hydrolytic equilibria quickly is to add appropriate equivalents of bases such as NaOH to Cr(III) salt solutions. 

This product gave satisfactory analytical values Calcd. for C8H17NO C, 67.1 H, 12.0. Found C, 67.2 H, 11.9. The neutral equivalent of various samples, titrated potentiometrically with standard hydrochloric acid solutions, ranged between 144 and 145 (calcd. 143.2). 

This stearolic acid has been thoroughly characterized 3 6 by the freezing-point curve, ultraviolet and infrared spectra, ozonization, and hydrogenation. It has been shown to be free both of positional isomers and of olefinic acids such as oleic and elaidic acids. Its properties include m.p. 46-46.5°, iodine number (Wijs titration, 30 minutes) 89.5, d 5 1.4510, d 5 1.4484, neutral equivalent 279.2-279.6 (theory 280.4), hydrogen uptake 95-100% of theory for a triple bond. The last trace of color is difficult to remove by recrystallization from petroleum ether. It can be removed, however, by crystallization from a 20-30% solution in acetone at —5 to —8°, or from an 8-10% solution at —20°, or by distillation (b.p. 189-190°/2mm.). 

The potassiiun /-butoxide prepared in this manner is a 1 1 complex with /-butyl alcohol neutralization equivalent calculated for (CH3)3COH-(CH3)3COK, 186. Found 184, 182. The complex can be isolated by simply removing the solvent at 20-25 mm. pressure on a steam bath. It can be stored for several months under a nitrogen atmosphere. 

The neutralization equivalent is a useful means of determining the molecular weight of a carboxylic acid. The process begins with a simple neutralization reaction of acid with standard base (usually sodium hydroxide). The reaction is... 

Indeed, there were those who described the azide coupling method as racemization-free. [15l However, this viewpoint proved to be overly optimistic. In 1970, Sieber reported that during a synthesis of calcitonin M by the azide method, significant epimerization occurred during two of the segment condensation steps in one of these reactions 40% of the epimerized product was observed. 16 There is a crucial detail in the experimental procedure here. The workers used tert-butyl nitrite to convert a peptide hydrazide into a peptide azide, but did not isolate the azide as was typical for research at that time. Instead, they neutralized the active intermediate in situ with DIPEA and added the amino segment for acylation. This demonstrates another important theme in the control of epimerization, the presence of a tertiary amine in the reaction mixture, even if only as a neutralization equivalent, can result in the formation of epimerized products. Indeed, most observations of racemization during... 

There is obtained 257-265 g. (88-91%) of />-toluenesulfonylan-t hranilic acid as a pale lavender powder with a neutral equivalent of 294-300, which indicates a purity of 97-99% (Note 3). This product is suitable for conversion to 2-aminobenzophenone, but it may be recrystallized by dissolving in hot 95% ethanol (10 ml. per g.) and then adding water (4 ml. per g.). The recovery in the first crop is about 75% of material melting at 229-230° and having a neutral equivalent of 295. 

The melting point of the />-toluenesulfonylanthranilic acid is not a good criterion of purity because the />-toluenesulfonic acid salt of anthranilic acid has about the same value. The neutral equivalents are widely different 154 for the salt and 291 for p-toluenesulfonylanthranilic acid. The compound obtained in this preparation gives a negative test for anthranilic acid on diazotization and treatment with alkaline /3-naphthol solution. The probable impurity is the sodium salt of -toluene-sulfonylanthranilic acid. 

Carboxylic acids dissolve in Na,CO, thereby evolving CO,. The neutralization equivalent or equivalent weight of a carboxylic acid is determined by titration with standard base it is the number of grams of acid neutralized by one equivalent of base. If 40.00 mL of a O.IOON base is needed to... 

The neutralization equivalent is found by dividing the weight of acid by the number of equivalents of base, i.e. 

Problem 16.89 What carboxylic acid (A) has a neutralization equivalent (NE) of 52 and decomposes on heating to yield CO, and a carboxylic acid (B) with an NE of 60 M... 

The glutaric acid obtained has a neutralization equivalent of 66.3 (theory 66.1) and is suitable for most synthetic work. 

The 5,5-(adipoyldiimino)-bis[2,4,6-triiodo-N-methylisophthalamic acid] was precipitated a second and third time from its sodium salt solution. The third precipitate was then dissolved in hot dimethylformamide (400 ml), and water (1.5 L) was slowly added. The mixture was digested and the hot mixture filtered, yielding a crystalline product which, after drying at 110°C, weighed 126.0 g (neutral equivalent, 724). This product was dissolved in dilute sodium hydroxide solution (1 L) and the solution was acidified (pH 5) and filtered into a hot stirred solution of hydrochloric acid (25 ml of concentrated acid in 75 ml water). The mixture was chilled and the solid collected, washed with water and dried at 110°C. Yield of 5,5-(adipoyldiimino)-bis[2,4,6-triiodo-N-methylisophthalamic acid] 114.0 g (45%). Melting point, 302°C (corrected), with decomposition. 

Crude 5-nitroisophthalic acid, monomethyl ester (46.3 g, 0.21 mole) was dissolved in 35% aqueous methylamine solution (500 ml). On standing, the orange solution became blood red. The reaction mixture was evaporated overnight on the steam bath, the cool residue was treated with 50 ml of water and the solution was acidified with hydrochloric acid. A yellow precipitate of crude N-methyl-5-nitroisophthalamic acid was separated and dried (yield 41.5 g). This acid was redissolved in dilute ammonia solution and the resulting solution (pH 5.2) was treated with charcoal. Acidification of the treated solution yield a pale yellow product of neutral equivalent 213. A small portion (10 g) was recrystaliized from 1 1 water-ethanol (300 ml) to yield orange N-methyl-5-nitroisophthalamic acid. M.p. 251°-252.5°C. 

The acid was spread out on a large filter paper and dried above a steam radiator for 48 hours. The literature reports the acid to be a monohydrate which loses its water of crystallization by drying at 120° for 3 hours. However, titration of the air-dried acid showed that it was not hydrated. A sample of the acid heated to 120° for 3 hours showed no change in neutral equivalent. 

The product secured by this procedure is free from sodium sulfate and isomeric sulfonic acids. Titrations of the first crop of crystals gave neutral equivalents ranging from 187.0 to 187.6 the calculated neutral equivalent is 187.2. The second crop is less pure since it had a neutral equivalent of about 177. 

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