Factor 2—The Base

PROBLEM 10.10 Fill in the trends for El and E2 reactions, comparing relative rates based on base strength  

These charts should look the same as the charts for factor 2 of substitution reactions. If you cannot figure it out without looking, you can always turn back to the last chapter, to Section 9.3. 

PROBLEMS Using the charts above, determine whether the following bases would favor an E2 or an EI. 

We saw in Chapter 8 (Section 8.3) that the difference between bases and nucleophiles is function. We even saw the difference between the terms nucleophilic-ity (which is a kinetic concept) and basicity (which is a thermodynamic concept). But there is another important difference between the strengths of bases and nucleophiles that you must know. Students rarely see this difference, and it causes them much unnecessary anguish when doing problems that involve substitution and elimination reactions at the same time (we will do problems like this in Chapter 12). Let s avoid the anguish by clearing up the difference now. 

Students generally assume that a stronger base is a stronger nucleophile. This is not always true. Basicity and nucleophilicity do not always parallel each other. Let s begin by seeing when they do parallel each other. 

---

Consider a veiiical 2 m-diameler cylindrical furnace whose stiifaces closely approximate black surfaces. The base, top, and side surfaces of the furnace are maintained at 400 K, 600 K, and 900 K, respectively. If the view factor from the base surface to the top surface is 0.2, the net radiation heat transfer between the base and the side suifaces is (a)22.5kW (b)38.6kW (c) 60.7 kW... 

The following subsections discuss simulation results regarding the salinity and salinity gradient effect. When we investigate the effect of a factor, we generally compare the results of live cases (systems), as defined in Table 8.2. The base case injection scheme is 1.0 pore volume (PV) water, 0.1 PV 3 vol.% surfactant solution, 0.4 PV 0.07 wt.% polymer solution, followed by 1.0 PV water injection. 

Several methods for determining have been described in the literature. If a suitable tracer is available, chromatograms at different flow rates should be measured. If parameter estimation is performed to obtain the axial dispersion coefficient or the factor 2, the complete model (including the plant peripherals and the column) as well as all parameters determined so far have to be taken into account. Another possibility is offered by a moments analysis (Section 6.5.3.1, Equation 6.134), which is based on exploiting the coimection between the axial dispersion coefficient and the second moment (Section 6.5.3.1) ... 

The EF algoritlnn [ ] is based on the work of Cerjan and Miller [ ] and, in particular, Simons and coworkers [70,1Y. It is closely related to the augmented Hessian (rational fiinction) approach[25]. We have seen in section B3.5.2.5 that this is equivalent to addmg a constant level shift (damping factor) to the diagonal elements of the approximate Hessian H. An appropriate level shift effectively makes the Hessian positive definite, suitable for minimization. 

The nucleophilicity of amine nitrogens is also differentiated by their environments. In 2,4,5,6-tetraaminopyrimidine the most basic 3-amino group can be selectively converted to a Schiff base. It is meta to both pyrimidine nitrogens and does not form a tautomeric imine as do the ortho- and /xira-amino groups. This factor is the basis of the commercial synthesis of triamterene. 

The mobility of the proton in position 2 of a quaternized molecule and the kinetics of exchange with deuterium has been studied extensively (18-20) it is increased in a basic medium (21-23). The rate of exchange is close to that obtained with the base itself, and the protonated form is supposed to be the active intermediate (236, 664). The remarkable lability of 2-H has been ascribed to a number of factors, including a possible stabilizing resonance effect with contributions of both carbene and ylid structure. This latter may result from the interaction of a d orbital at the sulfur atom with the cr orbital out of the ring at C-2 (21). 

The steric bulk of the base added to 2-methyl-4-phenylthiazole (171b) is another factor of the orientation for the kinetic metalation of 4-substituted 2-methylthiazoles (Table 1-60). Even though the C-5 proton... 

Radioisotope dilution assays are based on the principle of competition between radioactive labeled ( Co) vitamin B 2 and cobalamins extracted from matrices for binding sites on the intrinsic factor (a glycoprotein). Binding is in proportion to the concentration of the radioactive and nonradio active B 2 with the concentration of intrinsic factor as the limiting factor. Free cobalamins are separated from those bound on the intrinsic factor by absorption... 

This equation is based on the approximation that the penetration is 800 at the softening point, but the approximation fails appreciably when a complex flow is present (80,81). However, the penetration index has been, and continues to be, used for the general characteristics of asphalt for example asphalts with a P/less than —2 are considered to be the pitch type, from —2 to +2, the sol type, and above +2, the gel or blown type (2). Other empirical relations that have been used to express the rheological-temperature relation are fluidity factor a Furol viscosity P, at 135°C and penetration P, at 25°C, relation of (H—P)P/100 and penetration viscosity number PVN again relating the penetration at 25°C and kinematic viscosity at 135 °C (82,83). 

---