Spectroscopy aliphatic amines

The present procedure2 describes the conversion of resin-bound, primary aliphatic amines into isothiocyanates and the conversion of the latter into 3-aminothiophenes. The generation of isothiocyanates is related to known procedures,3 in which amines are first treated with carbon disulfide and the resulting dithiocarba-mates are desulfurized by treatment with a condensing agent (alkyl chloroformates, carbodiimides, lead or mercury salts, etc.). The presence of resin-bound isothiocyanates on the polystyrene support could be qualitatively ascertained by infrared spectroscopy (KBr-pellet strong absorption at 2091 cm-1). 

Several methods are available in the literature for the measurement of aliphatic amines in biological samples [28]. Problems with specificity and separation and cumbersome derivatisation and/or extraction procedures have limited the use of these techniques on a larger scale in clinical practice. The lack of a simple analytical method may have led to an underestimation of the incidence of the fish odour syndrome. For diagnosing the syndrome, an analytical technique should be used that is able to simultaneously and quantitatively measure TMA and its N-oxide in the complex matrix of human urine. Two such methods are currently available for this purpose proton nuclear magnetic resonance (NMR) spectroscopy and head-space gas analysis with gas chromatography or direct mass spectrometry (see below). 

HNMR spectroscopy has been used to distinguish between the two isomeric products obtained as a mixture in the reaction of 5,8-dichloro-2-phenylpyrimido[4,5-rf]pyridazine with aliphatic amines. In these reactions the isomeric products are separated by column chromatography and then the chemical shift of the H-4 proton is noted. This proton is shifted to lower field (ca. 8 10.2) for the 5-amino substituted products (39), when compared with the chemical shift (ca. 8 9.9) for the 8-amino substituted products (38) (72CPB1522). Chemical shifts for several pyrimido[4,5-rf]pyridazin-5-ones have also been reported (Table 2) (76BSF1549). 

The special types of bonding in three-membered ethyleneimine rings (41—43) have been studied using microwave spectroscopy (44—47), electron diffraction (48), and photoelectron spectroscopy (49—51), and have occupied theoretical chemists up to the present day (52). These studies reveal that ethyleneimine has a distincdy shortened C—C bond of 0.148 nm (as compared to 0.154 nm in open-chain compounds) and a noticeably lengthened C—N bond of 0.149 nm (compared to 0.146 nm). Because of the high s character of the free electron pair on the nitrogen, ethyleneimine also shows a lower basicity (p Ka = 7.98) than noncyclic aliphatic amines such as dimethyl amine (p Ka = 10.7) (53). 

The dependence of kp on the type of a-hydrogen is not known, nor can variations in ke be predicted easily. Mataga has studied amine quenching of triplet benzophenone by flash spectroscopy. N,N-dialkylanilines are the only amines which actually yield radical ions, and then only in polar solvents 157). He suggests two competing decay modes of the exciplex. Monoalkylanilines and tertiary aliphatic amines in any solvent and dialkylanilines in nonpolar solvents yield only radicals, presumably from the exciplex. Even though the oxidation potentials of tertiary aliphatic amines are so low that they quench triplet ketones at rates... 

Jeanmaire DL, Van Duyne RP (1977) Surface Raman spectroelectrochemistry 1. Heterocyclic, aromatic, and aliphatic-amines adsorbed on anodized silver electrode. J Electroanal Chem 84 1-20 Moskovits M (2005) Surface-enhanced Raman spectroscopy a brief retrospective. J Raman Spectrosc 36 485 96... 

Formation of the anhydride was shown unambiguously with FT-IR spectroscopy. No fluorine was detected by XPS and FT-IR methods, which supports formation of the interchain product339. The monolayer anhydride is quite stable and can survive treatment with water for at least 1-2 min. It can further react with aliphatic amines producing mixed anhydride of amide and acid. The reaction is rapid and quantitative the ratio of amide and acid in the resultant monolayer i s ca 1 1. 

The diamagnetic products are observed and can be characterized very well because the detection method is high-resolution NMR spectroscopy. On the other hand, the signal enhancement by the CIDNP effect mitigates the inherent low sensitivity of NMR. In consequence, even diamagnetic species that are unstable and thus present only in low concentration can be captured. An early example is the enol of acetophenone formed in the photoreaction of acetophenone with phenol [45], others are vinylamines in photoinduced hydrogen abstractions from aliphatic amines [46] (see Section V.B) and in the sensitized photoreactions of amino acids (Section V.G.l). 

With unsymmetrically substituted tertiary aliphatic amines, deprotonation can occur at different sites, and CIDNP spectroscopy was employed to measure relative group reactivities [94d]. For these complex reaction mechanisms, where two deprotonation routes can lead to the same products,... 

Other examples of the application of CIDNP spectroscopy to radical additions and substitutions include the self-substitution of quinones in the presence of tertiary aliphatic amines [111], the photoreactions between hexamethyldisilane and quinones [112], and the allylation of quinones via photoinduced electron transfer from allylstannanes [113] (see also Section V.E). Cycloadditions via radical ions are treated in a separate section (V.D.3). 

LB films of tetra-4-tert-butyl- and tetra-(3-nitro-5-tcrt-butyl)-substituted CoPcs were used to detect pyridine, primary aliphatic amines, and benzylamine, by means of microgravimetry, UV-Vis spectroscopy, and optic microscopy [59], The sorption occurs as stepwise intercalation of the sorbate molecules into the supramolecular 3D structure of the phthalocyanine assembly followed by formation of the donor-acceptor complexes. Both intercalation depth and stoichiometry of the complexes are determined by the molecular structure of amines. The supramolecular factor allows discrimination between amines in air but not in aqueous solutions because of concurrent intercalation of water. 

Fisher at al. [17] reported the use of on-line NMR spectroscopy with a flow probe for supercritical fluid chromatography (SFC) used for reaction monitoring purposes. They monitored aliphatic amines in SCCO2. A typical NMR spectrum reahzed both in classical media and in SCCO2 is presented in Fig. 5.6. 

The test is best used to distinguish primary aromatic and primary aliphatic amines from secondary and tertiary amines. It also differentiates aromatic and aliphatic primary amines. It cannot distinguish between secondary and tertiary amines. You will need to use infrared spectroscopy to make the distinction between secondary and tertiary amines. Primary aliphatic amines lose nitrogen gas at low temperatures under the conditions of this test. Aromatic amines yield a more stable diazonium salt and do not lose nitrogen until the temperature is elevated. In addition, aromatic diazonium salts produce a red azo dye when -naphthol is added. Secondary and tertiary amines produce yellow nitroso compounds, which may be soluble or may be oils or solids. Many nitroso compounds have been shown to be carcinogenic. Avoid contact and immediately dispose of all such solutions in an appropriate waste container. 

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