Ethane, functionalization

The BTEE-PMO (BTEE, l,2-bis(triethoxysilyl)ethane) functionalized with a bulky N-heterocyclic carbene was prepared by Hao et al. They were used as catalysts for the Suzuki coupling reaction. These materials also exhibited enhanced activity and selectivity [81]. The PdL (silylated carbapalladacycle precursor)-PMO was applied to the Suzuki reaction of p-bromobenzoic acid and phenylboronic add [65]. The results showed high catalyst activity with short reaction times compared to PdL-Si02 (synthesized by co-condensation of precursors and SiOj) due to the benefidal influence by increased porosity and regular distribution of the active site. 

Suppose we are using an empirical energy function such as the following to describe the inter- and intramolecular interactions in our ethanol/ethane thiol system ... 

Figure 1.8 Hindered rotation around a carbon-carbon bond, (a) The definition of (p (from 0 = 0) in terms of the ethane molecule, (b) The potential energy as a function of (p. (c) Here (p is shown (from (p = 0) for a carbon-carbon bond along a polyethylene backbone, (d) The potential energy for case (c) shown as a function of (p. [Panels (b) and (d) reprinted with permission from W. J. Taylor, J.Chem.Phys. 16 257 (1948).]...

Sketch the form of the potential energy as a function of torsional angle cj) for the torsional vibration in (a) ethane, (b) CH3NO2, (c) 2-fluorophenol, (d) CH2FOH, and... 

Fig. 3. Weight of coke formed (AQ and coking rate (r) in ethane cracking as a function of time (51).

As discussed in Sec. 4, the icomplex function of temperature, pressure, and equilibrium vapor- and hquid-phase compositions. However, for mixtures of compounds of similar molecular structure and size, the K value depends mainly on temperature and pressure. For example, several major graphical ilight-hydrocarbon systems. The easiest to use are the DePriester charts [Chem. Eng. Prog. Symp. Ser 7, 49, 1 (1953)], which cover 12 hydrocarbons (methane, ethylene, ethane, propylene, propane, isobutane, isobutylene, /i-butane, isopentane, /1-pentane, /i-hexane, and /i-heptane). These charts are a simplification of the Kellogg charts [Liquid-Vapor Equilibiia in Mixtures of Light Hydrocarbons, MWK Equilibnum Con.stants, Polyco Data, (1950)] and include additional experimental data. The Kellogg charts, and hence the DePriester charts, are based primarily on the Benedict-Webb-Rubin equation of state [Chem. Eng. Prog., 47,419 (1951) 47, 449 (1951)], which can represent both the liquid and the vapor phases and can predict K values quite accurately when the equation constants are available for the components in question. 

Figure 4.2. Rotational-energy barriers as a function of substitution. Tbe small barrier ( 2kcal) in ethane (a) is lowered even further ( O.Skcal) if three bonds are tied back by replacing three hydrogen atoms of a methyl group by a triple-bonded carbon, as in methylacetylene (b). The barrier is raised 4.2 kcal) when methyl groups replace the smaller hydrogen atoms, as in neopentane (c). Dipole forces raise the barrier further ( 15 kcal) in methylsuccinic acid (d) (cf. Figure 4.3). Steric hindrance is responsible for the high barrier (> 15 kcal) in the diphenyl derivative (e). (After...

The torsional strain is a sinusoidal function of the torsion angle. Torsional strain results from the barrier to rotation about single bonds as described for ethane on p. 56. For molecules with a threefold barrier such as ethane, the form of the torsional barrier is... 

Fig. 3.1. Potential energy as a function of torsion angle for ethane.

Magnesium triflate and zinc triflate are outstanding catalysts for the intro duction of the thioketal group for the protection of the ketone function [126] The reaction of a variety of ketones with ethane 1,2-dithiol in the presence of these triflates proceeds under mild conditions to form the corresponding thioketals in high yield (equation 62)... 

Estimate the cost of nonbonded HH repulsion as < function of distance by plotting energy (vertical axis) vs HH separation (horizontal axis) for methane+metham (two methanes approaching each other with CH bond head on ). Next, measure the distance between the nearest hychogens in eclipsed ethane. What is the HI repulsion energy in the methane chmer at this distance Multiplied by three, does this approximate the rotatioi barrier in ethane ... 

The parameter redundancy is also the reason that care should be exercised when trying to decompose energy differences into individual terms. Although it may be possible to rationalize the preference of one conformation over another by for example increased steric repulsion between certain atom pairs, this is intimately related to the chosen functional form for the non-bonded energy, and the balance between this and the angle bend/torsional terms. The rotational banier in ethane, for example, may be reproduced solely by an HCCH torsional energy term, solely by an H-H van der Waals repulsion or solely by H-H electrostatic repulsion. Different force fields will have (slightly) different balances of these terms, and while one force field may contribute a conformational difference primarily to steric interactions, another may have the... 

Reactor temperature is also a function of the feedstock used. Higher molecular weight hydrocarhons generally crack at lower temperatures than lower molecular weight compounds. For example, a typical furnace outlet temperature for cracking ethane is approximately 800°C, while the temperature for cracking naphtha or gas oil is about 675-700°C. 

The potential energy is often described in terms of an oscillating function like the one shown in Figure 10.9(a) where the minima correspond to the relative orientations in which the interactions are most favorable, and the maxima correspond to unfavorable orientations. In ethane, the minima would occur at the staggered conformation and the maxima at the eclipsed conformation. In symmetrical molecules like ethane, the potential function reflects the symmetry and has a number of equivalent maxima and minima. In less symmetric molecules, the function may be more complex and show a number of minima of various depths and maxima of various heights. For our purposes, we will consider only molecules with symmetric potential functions and designate the number of minima in a complete rotation as r. For molecules like ethane and H3C-CCI3, r = 3. 

The six-term radial distribution function for ethane (Fig. 1, curve A) shows maxima at 1.16,... 

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