System triethylamine

OCOH)(PH3)2 and a dihydrogen molecule [44], The introduction of a NH3 molecule in the system converts this single-step process in a three-step process, with three transition states. The energy change occurs smoothly and the highest barrier is only 2.1 kcal/mol (MP2//MP2) which is much smaller than the barrier in the absence of NH3 (11.4 kcal/mol, Table 4). This means that the four-center metathesis occurs with nearly no barrier in the presence of base. However, the base effects are likely overestimated in this calculations. The experimental triethylamine system cannot do all the interactions ammonia does, and polar or protic solvents should weaken the interaction between the base and the complex. 

Reaction of quinoxaline with the fluorine-iodine-triethylamine system gives 2-fluoroquinoxaline 40 and 2,3-difluoroquinoxaline 41, whose yields depend on the fluorine usage (Equation 6) <1999J(P1)803>. Using 6-chloro-quinoxaline or 6,7-dichloroquinoxaline as the substrate, the monofluoro product is predominantly formed regardless of the amount of fluorine used. It is suggested that the reaction proceeds via attack of the fluoride ion on the a-carbon of an intermediate A -iodo quinoxalinium species followed by elimination of hydrogen iodide with triethylamine. 

Photoreduction of benzophenone by primary and secondary amines leads to the formation of benzpinacol and imines [145]. Quantum yields greater than unity for reduction of benzophenone indicated that the a-aminoalkyl radical could further reduce the ground state of benzophenone. Bhattacharyya and Das confirmed this in a laser-flash photolysis study of the benzophenone-triethylamine system, which showed that ketyl radical anion formation occurs by a fast and a slow process wherein the slow process corresponds to the reaction of a-aminoalkyl radical in the ground state of benzophenone [148]. Direct evidence for similar secondary reduction of benzil [149] and naphthalimides [150] by the a-aminoalkyl radical have also been reported. The secondary dark reaction of a-aminoalkyl radicals in photo-induced electron-transfer reactions with a variety of quinones, dyes, and metal complexes has been studied by Whitten and coworkers [151]. 

An example of this kind of behaviour is found in the formic acid 4-triethylamine system, ) while certain intermetallic compounds such as KZui2, KPbg show similar behaviour except that the liquid phase has an upper critical solution temperature. J... 

The system 2-naphthylamine/triethylamine forms proton donor/acceptor interaction, which was investigated in the excited state by measuring time-resolved fluorescence spectra. While the similar 2-naphthol/triethylamine system affords the ion pair interaction, via the hydrogen bond complex, the 2-naphthylamine/triethylamine system presents hydrogen bond interaction which shows a low-temperature absorption with 7max = 370 nm, and Amax = 370 nm in the fluorescence spectrum148. 

This system was used for illustration in the first edition. The figures which appear below are from that source. [I changed to the hexane-triethylamine system since the x andy were too close in the benzene-ethylene chloride system because the pure component vapor pressures are so close.]... 

As the first illustration of the use of these equations, consider vapor-liquid equilibrium in the hexane-triethylamine system at 60°C. These species form an essentially ideal mixture. The vapor pressure of hexane af this temperature is 0.7583 bar and that of triethylamine is 0.3843 bar these are so low that the fugacity coefficients at saturation and for the vapor phase can be neglected. Consequently, Eqs. 10.1-3 and 10.1-4 should be applicable to this system. The three solid lines in Fig. 10.1-1 represent the two species partial pressures and the total pressure, which were calculated using these equations and all are linear functions of the of liquid-phase mole fraction the points are the experimental results. The close agreement between the computations and the laboratory data indicates that the hexane-triethylamine mixture is ideal at these conditions. Note that this linear dependence of the partiaLand total pressures on mole fractions predicted by Eqs. 10.1-2 and 10.1-3 is trae only for ideal mixtures it is not true for nonideal mixtures, as we shall see in Sec. 10.2. 

Figure 10.1-1 Equilibrium total pressure and species liquid-phase fugacides (Xj ) versus mole ffacdon for the essentiaOy ideal hexane-triethylamine system at 60°C. [Based on data of J. L. Humphrey and M. Van Winkle. J. Chem. Eng. Data, 12,526 (1967).]...

Figure 10.1-3 Pressure-composition diagram for the hexane-triethylamine system at fixed temperature.

Few liquid mixtures are ideal, so vapor-liquid equilibrium calculations can be more complicated than is the case for the hexane-triethylamine system, and the system phase diagrams can be more structured than Fig. 10.1-6. These complications arise from the (nonlinear) composition dependence of the species activity coefficients. For example, as a result of the composition dependence of y, the equilibrium pressure in a fixed-temperature experiment will no longer be a linear function of mole fraction. Thus nonideal solutions exhibit deviations from Raoult s law. We will discuss this in detail in the following sections of this chapter. However, first, to illustrate the concepts and some of the types of calculations that arise in vapor-liquid equilibrium in the simplest way, we will assume ideal vapor and liquid solutions (Raoult s law) here, and then in Sec. 10.2 consider the calculations for the more difficult case of nonideal solutions.. ... 

Our first approach [51] to azetidine-2,3-diones relies on the silatropic rearrangement of trimethylsilyl a-hydroxyacetates 87 into the thermodynamically more stable a-trimethylsilyloxyacetic acids 88. The [2 H- 2] cycloaddition step was carried out by means of phenyl dichlorophosphate reagent in yields being in the range 40-65%. Under these conditions, the P-lactam 91 was produced in 45% yield as the single cis isomer. To transform 91 into 93 dimethylbromosulphonium bromide-triethylamine system [52] furnished the desired a-keto P-lactam in 90% yield. 

Phase transfer agents were chosen to give a broad representation of available agents. Typical results appear in Table 3. Addition of PTA s to the triethylamine systems typically led to lower yields and shorter chains except for 18-Crown-6 where the yield was the highest obtained, about double that obtained without the crown ether (Table 4). For the disodium terephthalate systems, addition of a PTA typically leads to a lowering of yield but a substantial increase in chain length when employing 15-Crown-5 (Table 5). 

The mechanism of solvation of the DMSO-chloral-triethylamine system for cellulose has been studied. U.v. spectroscopic studies showed that the colour of the system was dependent upon the amount of cellulose present. Even when large quantities of triethylamine were present cellulose was not degraded to a significant extent. 

The initial velocity of quinuclidine substitution is significantly faster than that of triethylamine at the same temperature (Table III, runs 21-23), even though the former was investigated in a mixed solvent. Similar results were found in the quaternization of the model compound. If a steric effect were considered to be the sole factor producing the decrease in k with respect to kQ, one would expect that (1) hQ/k2 for quinuclidine substitution should be smaller than hQ/k2 for TEA substitution and/or (2) the initial linearity in the second order plot would extend beyond 52% conversion where deviation occurs in the triethylamine system. Experimental results refute these expectations rate retardation is enhanced in quinuclidine reactions, furtherfore, the break point is almost the same for both cases. 

The equilibrium constant K3 correlates well with the value of ApK in water. Ion-pairs are more strongly favoured as the polarity of the solvent is increased for example, in the case of the p-nitro-phenol-triethylamine system, ion-pairs are only formed in significant amounts when e > 6. Further evidence for ion-pairing is shown by dipole moments [20] moments of 10-18 D are observed when proton transfer is indicated, these values being of the same order as fpr tetra-alkylammonium salts, R4N X [21]. 

The hydrogen sources typically used for these reactions are IPA and a base, or formic acid-triethylamine. The IPA system is reversible, which can lead to erosion of enantioselectivity over time. One way to counter this is to operate at high dilution so there is a large excess of IPA however, this would not be desirable on an industrial scale where throughput is key. This problem can be overcome by removal of acetone during the reaction, which can be achieved in a variety of ways. The formic acid-triethylamine system is irreversible and therefore does not suffer from this issue. However, other factors have been shown to be important in achieving an efficient process, such as the ratio of formic acid to triethylamine and effective removal of the carbon dioxide generated, which reacts reversibly with the hydride complex formed. ... 

Bisht, P.B., Joshi, G.C., and Tripathi, H.B. (1995). Excited state hydrogen bonding of the 2-naphthol-triethylamine system in 1,4-dioxane. Chem. Phys. Lett. 237 356-360. 

---