Ethyl amines, ionization

For esters, deprotonation is effected with triethyl amine (which favors E2), while El ionization is disfavored because it requires moving the bulky terr-butyl group into planarity. For thioesters, Ei reaction is facilitated by the thiophenyl group, while E2 reaction is slowed by use of the bulky diisopropyl ethyl amine. ... 

The formation of solvent—analyte noncovalently bound complexes (e.g., [M -F H + ACN], [M -F H -F MeOH]", etc.) complicates molecular ion determination in ESI—APCI MS (Table 10.1). The relative abundances of these solvent cluster ions depend on the components in the solution phase, ionization mode, spray voltage, capillary temperature, sheath gas pressure, as well as auxiliary gas flow. Zhao et al. (2004) recently reported that acetonitrile could be reduced to ethyl amine under ESI conditions (Scheme 1). They demonstrated that the M -F 46 ion in the mass spectrum represented the ethyl amine adduction ([M -F H -F CH3CH2NH2] ) when the ESI—MS was performed by infusion of the compound in acetonitrile and water (1% HCOOH -F 1% NH4OH) (1 1 V v). Moreover, they showed the same analyte produced a moderate [M + H + CD3CH2NH2] (M -F 49) signal when acetonitrile-ds was used as the organic solvent (Scheme 1). 

Although the conventional mass spectra of the five C- nitro derivatives of indazole are nearly identical, the corresponding metastable peak shapes associated with the loss of NO-can be used to differentiate the five isomers (790MS114). The protonation and ethylation occurring in a methane chemical ionization source have been studied for a variety of aromatic amines, including indazoles (80OMS144). As in solution (Section 4.04.2.1.3), the N-2 atom is the more basic and the more nucleophilic (Scheme 5). 

Despite this superficial similarity, however, subtle differences between the behaviour of ionized amines and the analogous ionized alcohols and ethers remain. Thus, metastable ionized 2-butylamine loses 80% ethane in contrast, ionized 2-butanol eliminates both ethane (35%) and methane (40%)85. The latter reaction corresponds to loss of the smaller methyl group and an a-hydrogen atom from the larger ethyl substituent at the branch point. Methane loss does not occur from ionized amines with a methyl substituent on the -carbon, with the solitary exception of ionized isopropylamine which does expel methane (10%). However, ionized 3-hexylamine eliminates both ethane (35%) and propane (20%)85. 

The stability of the complex is proportional to the hydrophobic character of the substituents thus, a methyl or ethyl substituent will increase the stability. Hydroxyl groups hinder complex formation, and their hydrophilic effects decrease in the OKstthio> meta> para. In the case of amine groups, it is important whether they are present in their neutral form or ionized form. Ionic species usually do not form stable complexes (Szejtli, 1982). 

The ionization constants,331 NMR spectra,174 and mass spectra1227 of representative amino-1,6-naphthyridines have been compared with those of related amino derivatives. Complexes of l,6-naphthyridin-2-amines with tetracyanoquinodi-methane have been studied.416 4-(3-Dimethylamino-l-methylpropylamino)-l,6-naphthyridine showed significant antimalarial activity.236 X-ray analyses of a number of 5-amino-1,6-naphthyridines have been reported in connection with their antibacterial activities for example, ethyl 5-amino-7-benzylseleno-8-cyano-4-(fur-2-yl)-l,2-dimethyl-l,4-dihydro-l,6-naphthyridine-3-carboxylate (10) proved to be a mixture of two symmetric conformers in each crystal 772 the other related compounds appear to be composed of single conformers.558,560 562 759 781 1289... 

The stereochemical control exerted by migrating methyl in the deamination of l-ethyl-2-methylbutylamine (661) is also informative457. Since the decomposition of the diazonium ion is unassisted, only 28% of the 4-methyl-3-hexanol arises by a 1,2-methyl shift (concerted ionization leading directly to the methyl-bridged ion (662) would require 50%). An excess of (35,4S)-(664) over (3R, 4R)-(664) is obtained (72 28) and substantial crossover from threo- amine to erj> thro-alcohol occurs. The ery thro-alcohol, however, is enantiomerically pure (3R, 4S)—(664). Although the... 

Derivatization is also useful to detect volatile metabolites. Liu et al. [282] described a specific, rapid, and sensitive in situ derivatization solid-phase microextraction (SPME) method for determination of volatile trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCOH), in rat blood. The metabolites were derivatized to their ethyl esters with acidic ethanol, extracted by SPME and then analyzed by gas chromatography/negative chemical ionization mass spectrometry (GC-NCI-MS). After validation, the method was successfully applied to investigate the toxicokinetic behavior of TCE metabolites following an oral dose of TCE. Some of the common derivatization reagents include acetyl chloride and TV-methyl-iV- ft-b u (y Idi methyl si I y I) tro (1 uoroacctam i nc (MTBSTFA) for phenols and aliphatic alcohols and amines, dansyl chloride and diazomethane for phenols, dansyl chloride for amines, acidic ethanol and diazomethane for carboxylic acids, and hydrazine for aldehydes. 

This type of interaction is possible with thiophenol and anthracene whose ionization potentials are, respectively, 8.3 and 7.5 eV [345], but less probable with ethyl- and butylamine which have ionization potentials close to that of pyridine (respectively, 9.19 and 8.79) [345]. Amines and thiophenol can also interact with the radicals formed in the polymer according to... 

Yamamoto et al. (1982) developed a quantitative method for the determination of putrescine, cadaverine, spermidine, and spermine in foods. Separation of the amines from foods was achieved by eluting through a cation-exchange resin column and then converted to their (ethyloxy) carbonyl derivatives by the reaction with ethyl chloroformate in aqueous medium before application to the gas chromatograph with a flame ionization detector. They used 1,8-diaminooctane as an internal standard and performed the separation and determination of the resulting derivatives on a 1.5% SE-30/0.3% SP-1000 on Uniport HP column (0.5 m) under the temperature-programmed condition. Staruszkiewicz and Bond (1981) developed a GLC procedure for the quantitative determination of the diamines putrescine... 

Cyclic Amines Similar to cycloketones [reaction (6.43)], the first step in the fragmentation of ionized cyclic amines is a-cleavage of the C—C bond next to the C—N bond to produce a distonic ion [20]. Subsequent fragmentation proceeds via the loss of an alkene molecule or via an H-transfer followed by the loss of an alkyl radical. A typical example of the latter fragmentation is the loss of an ethyl radical from the cyclopentylamine radical cation. Ionized cyclic amines also exhibit an abundant (M - 1) ion from loss of the a-H (see Figure 6.8). As exemplified for piperidine, cyclic amines also participate in these generic fragmentation reactions of heterocyclic compounds [reaction (6.42)]. 

Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) is usually used as weak polyelectrolyte for gene delivery and has the additional property of being temperature sensitive [140, 141]. The study by Stolnik and coworkers on PDMAEMA (Fig. 7a) emphasized the condensation behavior of PDMAEMA as a function of pH [102]. As can be intuitively understood, the ionization of PDMAEMA increases from pH 8 (only 24% ionization) to pH 4 (polycation nearly completely ionized), therefore the binding of PDMAEMA with DNA is tighter (EtBr displacement assay) at lower pH, which is counterproductive when it comes to release of the genetic material. But, this effect is balanced by its buffering capacity via the tertiary amine groups, which is favorable for endosomal escape. 

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