Amines measurement

The trends that are evident, especially from basicities of amines measured in the gas phase, point to increasing basicity with the number and size of alkyl groups on the nitrogen atom. 

Less optimistic conclusions about the performance of the DFT/PCM scheme were drawn in a study of solvent effect on the optical rotation of (.S )- -mclhy I benzyl amine [67]. The authors compared the optical rotation of this amine measured in 39 different solvents (whenever possible extrapolated to infinite dilusion) with the results obtained by means of IEF-PCM with the B3LYP functional and the aug-cc-pVDZ basis set. They observed substantial discrepancies for many of the hydrogen-bond forming solvents (which is not... 

Figure 6.32 Cyclic voltammogram of a nanocrystalline TiC electrode modified with a electroactive aromatic amine, measured at a scan rate of 2 mV s 1. The electrolyte is acetonitrile containing 0.5 M lithium bis(trifluoromethylsulfonyl)imide. Reprinted with permission from P. Bonhote, E. Gogniat, S. Tingry, C. Barbe, N. Vlachopoulos, F. Lenzmann, P. Comte and M. Gratzel, /. Phys. Chem., B, 102,1498 (1998). Copyright (1998) American Chemical Society...

A number of organic compounds have been identified as products of DON photodegradation. In the majority of published papers, they are characterized in bulk as amines measured as fluorescent ortho-phtaldialdehyde derivatives (Lindroth and Mopper, 1979). Figure 10.5 shows one of the few cases where organic products of DON phototransformation are presented as chemical moieties identified at the molecular level. 

Delmas, D., Frickla, M. G., and Linley, E. A. S. (1990). Dissolved primary amine measurement by flow injection analysis with o-phthaldialdehyde Comparison with high performance liquid chromatography. Mar. Chem. 29, 145—154. 

The use of probe molecules that will sorb on specific acid sites has also been used to differentiate Brpnsted and Lewis sites. Studies on H-ZSM-5 and H-ZSM-8 suggest that pyridine cannot access the Lewis sites and thus essentially measures Brpnsted acidity 2,6-Dimethylpyridine has been reported to sorb preferentially on the Brpnsted sites of a variety of zeolites. Various amines have also been used to measure surface acidity. Since amines are weaker bases than either ammonia or pyridine, they preferentially sorb on the stronger acid sites. Both n-butyl amine and t-butyl amine have been used as adsorbates in TPD studies of zeolites. Comparison of the TPD spectra with butene isomerization has shown that butyl amines measure only the strong acid sites. 

Figure 3.2. Fick diffusion coefficient D as a function of temperature for the system water-triethyl-amine. Measured data for Fick diffusivity D at constant composition = critical composition X2 = 0.0874. Critical temperature = 18.3°C. Data from Haase and Siry (1968).

Table 11. chemical shifts for a series of primary and secondary amines measured using N-optimized CIGAR-HMBC ... 

TABLE 13. Gas-phase proton affinities for some silyl substituted amines, measured by pulsed ion cyclotron resonance64... 

Figure 2.47. IR spectra of dodecylamine adsorbed during 5 min from 10" M aqueous solution on (a-c) powdered quartz and (of) polished quartz surface. DRIFTS of undiluted quartz powder (a) -150 -E 38 (jim and p) -5 urn size (200 scans) (c) DRIFTS of -5 ixm size but diluted in the 1 5 ratio by KBr (200scans) (cf)s-polarized IRRAS spectrum of polished surface after treatment with amine, measured at = 70° (500 scans). Background spectmm is (a) and p) initial quartz powder (c) KBr (d) freshly polished quartz surface.

Table 3.2. Electron-nuclear relaxation times in amines measured after addition of reagent. (Values normalized to a viscosity of IcP and expressed in cPs units (L 34))...

Reduction of a nitro compound to a primary amine. In a 50 ml. round-bottomed or conical flask fitted with a reflux condenser, place 1 g. of the nitro compound and 2 g. of granulated tin. Measure out 10 ml. of concentrated hydrochloric acid and add it in three equal portions to the mixtiue shake thoroughly after each addition. When the vigorous reaction subsides, heat under reflux on a water bath until the nitro compound has completely reacted (20-30 minutes). Shake the reaction mixture from time to time if the nitro compound appears to be very insoluble, add 5 ml. of alcohol. Cool the reaction mixture, and add 20-40 per cent, sodium hydroxide solution imtil the precipitate of tin hydroxide dissolves. Extract the resulting amine from the cooled solution with ether, and remove the ether by distillation. Examine the residue with regard to its solubility in 5 per cent, hydrochloric acid and its reaction with acetyl chloride or benzene-sulphonyl chloride. 

Note that for 4.42, in which no intramolecular base catalysis is possible, the elimination side reaction is not observed. This result supports the mechanism suggested in Scheme 4.13. Moreover, at pH 2, where both amine groups of 4.44 are protonated, UV-vis measurements indicate that the elimination reaction is significantly retarded as compared to neutral conditions, where protonation is less extensive. Interestingy, addition of copper(II)nitrate also suppresses the elimination reaction to a significant extent. Unfortunately, elimination is still faster than the Diels-Alder reaction on the internal double bond of 4.44. 

In the flask were placed 10.0 g of the propargylic amine (see Chapter lIII-5, Exp. 1). The air in the flask was replaced with nitrogen and a solution of 0.01 mol of KO-tert.-Ci,H,3 in 10 g of THF (free from hydroperoxide) was added. The mixture was warmed at about 40 C. A weakly exothermic reaction was observed and the temperature rose to about 45°C. After 1-2 min the gel originally present, had disappeared almost completely and a brown solution had formed. The refractive index of the solution (note 1) was measured after intervals of about 2 min. After the... 

Basicity of Amines As Measured by the of Their Conjugate Acids ... 

Basicity constant Ki, (Section 1 14) A measure of base strength especially of amines... 

If the liquid that is being bombarded contains ions, then some of these will be ejected from the liquid and can be measured by the mass spectrometer. This is an important but not the only means by which ions appear in a FAB or LSIMS spectrum. Momentum transfer of preformed ions in solution can be used to enhance ion yield, as by addition of acid to an amine to give an ammonium species (Figure 4.3). 

Table 4 lists the specifications set by Du Pont, the largest U.S. producer of DMF (4). Water in DMF is deterrnined either by Kad Fischer titration or by gas chromatography. The chromatographic method is more rehable at lower levels of water (<500 ppm) (4). DMF purity is deterrnined by gc. For specialized laboratory appHcations, conductivity measurements have been used as an indication of purity (27). DMF in water can be measured by refractive index, hydrolysis to DMA followed by titration of the Hberated amine, or, most conveniendy, by infrared analysis. A band at 1087 cm is used for the ir analysis. 

Polymerization. The polymerization of aziridines takes place ia the presence of catalytic amounts of acid at elevated temperatures. The molecular weight can be controlled by the monomer—catalyst ratio, the addition of amines as stoppers, or the use of bifimctional initiators. In order to prevent a vigorous reaction, the heat Hberated during the highly exothermic polymerization must be removed by various measures, ie, suitable dilution, controlled metering of the aziridine component, or external cooling after the reaction has started. 

The free maleic acid content in maleic anhydride is determined by direct potentiometric titration (166). The procedure involves the use of a tertiary amine, A/-ethylpipetidine [766-09-6J, as a titrant. A tertiary amine is chosen as a titrant since it is nonreactive with anhydrides (166,167). The titration is conducted in an anhydrous solvent system. Only one of the carboxyhc acid groups is titrated by this procedure. The second hydrogen s dissociation constant is too weak to titrate (166). This test method is not only used to determine the latent acid content in refined maleic acid, but also as a measure of the sample exposure to moisture during shipping. 

Odors are measured by their intensity. The threshold value of one odor to another, however, can vary greatly. Detection threshold is the minimum physical intensity necessary for detection by a subject where the person is not required to identify the stimulus, but just detect the existence of the stimulus. Accordingly, threshold deterrninations are used to evaluate the effectiveness of different treatments and to estabflsh the level of odor control necessary to make a product acceptable (8). Concentration can also produce different odors for the same matenal. For example, indole (qv) in low concentrations has the smell of jasmine and a low threshold of perception. In high concentrations, it has a strong odor of feces and CX-naphthyl amine as well as a considerably higher threshold of perception. 

Tertiary amines are also effective as accelerators in cobalt redox systems to advance the cure rate (Eig. 6). Hardness development measured by Shore D or Barcol D634-1 penetrometer can be used to demonstrate this benefit, which is useful in increasing mold turnover at ambient temperatures. 

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). 

Because the heavy ethyleneamines are very complex materials, assays by titration in aqueous and nonaqueous media are often performed (151). The result is usually expressed as an amine number or amine value, a measure of the total basic nitrogen content of the product. Titrimetric procedures are also available to define primary, secondary, and tertiary amine content (152). 

Aminoisoxazoles can be determined photometrically by reaction with sodium 1,2-naph-thoquinone-4-sulfonate and selective extraction of the resulting dye into CCI4 for absorbance measurements. This class of compound can be determined in the presence of sulfonamides, sulfanilamides, hydroxylamines and other select amines (74MI41610). 

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