Alkylamines ionized

Reactions of immonium ions derived from ionized alkylamines. . . 226... 

This 1,2-NH3 migration is the key step in the reorganization of the heavy atom skeleton which precedes pseudo-a-cleavage of ionized long-chain alkylamines (Scheme 3). The transition state for this process may be considered to resemble a tight complex of an ionized alkene (ethylene in the case of the archetypal /J-DI, CH2CH2NH3+) and NH3 (equation 9). This idea is consistent with the behaviour of adduct ions [C H2 NH3]+ generated by direct combination of the appropriate ionized alkene and NH3 58,59. 

Similarly, ionized alcohols and ethers containing a chain of at least three contiguous carbon atoms attached at one end to the oxygen atom frequently expel water or the alcohol derived from the smaller alkyl group76-80. However, the corresponding ionized amines rarely eliminate ammonia or small alkylamines in great abundance. This contrast reflects energetic factors. Water and small alcohols are extremely stable molecules (AHf = —240 and —190 kJ mol-1, respectively, for water and methanol), but ammonia and methylamine are not particularly stable (AHf = —20 and —25 kJmol-1, respectively)82,83. Moreover,... 

As noted previously, ionized primary and secondary alkylamines isomerize to DIs provided they have sufficiently long alkyl chains and are allowed enough time. These... 

The most important example of alkene elimination is found for ionized 1-pentylamine, for which propene loss is the dominant fragmentation of metastable ions. However, this channel is not of general importance metastable ionized 1-butylamine eliminates a much smaller proportion (15%) of ethylene and higher homologues of metastable ionized n-pentylamine rarely expel alkenes to any appreciable extent44. Nevertheless, [M — C H2 ]+ ions do appear in LELT spectra of long-chain primary alkylamines (e.g. at m/z 31, 45, 59, 73, 87 and 101 for 1-octylamine, Figure 2)113. 

There are two pieces of evidence suggesting that ionizable groups are responsible for at least a part of the problem. First, the measured solubilities are generally higher than the predicted values, and charged species are expected to be more soluble than the unionized species. Second, most of the compounds for which the predictions are poorest are alkylamines (206 of 316 compounds where the measured solubility is at least 100-fold greater than the predicted solubility). On the other hand, even if we remove... 

Substrates for CYP2D6 include tricyclic antidepressants, p-blockers, class 1 anti-arrhythmics. In brief, the structural similarities of many of the substrates and inhibitors in terms of position of hydroxylation, overall structure (aryl-alkylamine) and physicochemistry (ionized nitrogen at physiological pH), have allowed template models such as that illustrated as Figure 7.3 to be constructed. 

Reversed-phase ion-pair chromatography is primarily used for the separation of mixtures of ionic and ionizable compounds. In this chromatographic mode, a pairing ion is added to the mobile phase in order to modulate the retention of the ionic solutes. The pairing ion is an organic ion such as alkylsulfonate, alkylsulfate, alkylamine, tetraalkylammonium ion, etc. Here, only a very brief description of the main ideas behind the electrostatic model for ion-pair chromatography is presented. For a complete discussion, the reader is referred to Ref. [7,8] and the references therein. 

Here we are concerned mainly with alkylamines. Detailed SCF charge analyses [43] indicate that any gain in total charge translates into a downfield shift, which is the trend exhibited by alkylamines, but also by nitroalkanes and isonitriles. Examples are offered in Table 6.5 (see also Fig. 6.6), along with pertinent ionization potentials, indicated in kcal/mol ... 

The relative ranking of the activators roughly parallels the ionization potential values listed in Table 1 for example, phosphine > arsine > alkylamine. 

Detector will have response to ionizable compounds such as aromatics and unsaturated organics, some carboxylic acids, aldehydes, esters, ketones, silanes, iodo- and bromoalkanes, alkylamines and amides, and some thiocyanates... 

Ionized compounds are usually much less retained than noncharged compounds their separation in RP chromatography is usually possible only with ionic additives to the mobile phase. Basic compounds can interact with residual sUanols in alkyl sihca-bonded phases ionized to SiO anions consequently, strong retention and tailing peaks are observed. Alkylamine additives to the mobile... 

Eksborg and Schill1 separated a series of alkylamines on a cellulose column loaded with a 0.06 M aqueous picrate solution, of pH 11.2, using as mobile phase chloroform - 1-pentanol (19 1). Addition of the alcohol to the mobile phase was necessary to reduce tailing. Celite and porous silica gel were found to be less suitable as solid support for aqueous picrate solutions. At the low pH necessary to ionize tertiary, secondary and primary amines, picrate... 

IP-RPLC with TrBA is suitable for the LC-MS analysis of the degradation products of dyes. " However, the alkylamines used for ion-pairing need to be volatile, which limits the number of carbons they can bear. Contrary to the tetraalkylammonium counter-ions, di- and tri-alkylamines do not tend to form adducts in modern API interfaces. Instead, they can act as H donors in their ammonium form and may then influence the ionization process of sulfonates in by decreasing the sensitivity of detection. " " In the same way, these amines diminish the risk of sodium adduct formation and of multiple charging. Due to their suppression effect, the concentration of alkylamines should be reduced to the lowest level acceptable for chromatographic retention. 

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