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Relative reactivities with

TABLE III-37. COMPARISON OF THE RELATIVE REACTIVITIES (WITH RESPECT TO BENZENE) OF VARIOUS PYRIDINE SUBSTRATES towards PHENYL AND 2-THIAZOLYL RADICALS AT 70 TO... [Pg.373]

The relative reactivities with respect to nucleophilic SAE displacement increase in the order Cl < Br < I < F. The relative reactivities of nucleophiles are illustrated by the reactions of 2-bromopyridine replacement by the following groups occurs under the conditions given (an indicates that the product spontaneously tautomerizes) ... [Pg.284]

The values of th2o s,h2o in Table II indicate a value for th2o ranging from 10 9 to 10 10 sec., based on a value for s.h,o of 6 X 10 M 1 sec."1 from Debye s equation (11). The constants in Table II are also a measure of the relative reactivity of solute with H20 for any particular form of radiation for which th2o can be considered a constant. The relative reactivities of solute with H20 and e aq for Co60 7-radiation differ slightly but significantly as shown in Table III. Relative reactivities with e aq are based on measurements of absolute rate constants by pulsed-radiolysis techniques (4). [Pg.281]

The quinone methide carbon of 71 is also the terminal carbon of an extended enol, and therefore reacts as both a nucleophile and electrophile (Scheme 32). This carbon shows a higher relative reactivity with electrophiles compared with nucleophiles than is observed for the corresponding terminal quinone carbon of mitomycins (Scheme 30A).73 Furthermore, the addition of nucleophiles to 71 is readily reversible, but the nucleophile adduct can be trapped by reoxidation to... [Pg.66]

Now, there is no satisfactory theory of steric effects, although attempts to rationalize the barrier of ethane by quantum-mechanical calculations are appearing more frequently (dementi and Davis, 1966). Furthermore, simple group-additivity schemes of various kinds have had limited success, at best, e.g. for estimating rotational barriers in ethanes (Tang and Chen, 1962), correlating relative reactivities with Taft EB values (Wells, 1963), or evaluating asymmetric induction (Ugi, 1965 Ruch and Ugi, 1966). Semi-empirical calculations by equation (197) have... [Pg.308]

Competition Between Pollutants. Competition between several organic pollutants may affect the photocatalytic degradation rate of each species, depending on whether the process is limited by the irradiation or by the total organic matter. The factors intervening in the competition are the respective concentrations, the partition coefficients between the fluid phase and the adsorbed phase, and the relative reactivities with respect to the active species. Consequently, interference effects may or may not be observed. [Pg.110]

Bromopro- kots" k. Relative Relative Reactivity ° with... [Pg.288]

Electrophilic reagents are Lewis acids (- acid-base theories). Electrophilic catalysis is catalysis by Lewis acids. The term electrophilic is also used to designate the apparent polar character of certain -> radicals, as inferred from their higher relative reactivities with reaction sites of higher -> electron density. See also -> electrophilicity. Ref. [i] Muller P (1994) Pure Appl Chem 66 1077... [Pg.235]

The term electrophilic is also used to designate the apparent polar character of certain radicals, as inferred from their higher relative reactivities with reaction sites of higher electron density. [Pg.95]

By analogy with butadiene, we might expect an aptitude kinetically for reaction in the s-cis conformation. This has barely been looked at lithium in ammonia reduction of various a,/3-unsaturated ketones gives mixtures of the E- and Z-enolates possibly reflecting the proportions of the s-trans and s-cis conformers, respectively, in the starting material as well as their relative reactivity with respect to accepting an electron. There is, however, some evidence that the proportion of Z-enolate is a little higher than the proportion of s-cis conformer.169... [Pg.109]

Relative reactivity with R aeruginosa nitrite reductase... [Pg.543]

The first variable in catalytic hydrogenation is the catalyst. The most commonly used heterogeneous catalysts are platinum, palladium, nickel, rhodium, nickel, and ruthenium. Rylander gave references for the preparation of the most common catalysts, shown in Table 4.14.31 In some cases, salts of transition metals are used rather than the metal itself although the pure metal adsorbed on a support (see above) is also commonly used. Hudlicky presented an order of relative reactivity with propene for groups 8-10 (VIII) transition metal catalysts,341 based on the work of Mann and Lien.342 xhe order given is ... [Pg.370]

T lf2K Electrochemical corrosion studies nave been completed with these electrodes and relative reactivity with water of each phase has been assessed. Freshly surfaced electrodes display facile room temperature electron transfer between superconductor phases and both solution redox species and surface confined electroactive polymers. This work should lay the grounds for construction of novel molecular film/superconductor junctions irtiich can be studied at a variety of temperatures. [Pg.207]

In the examples discussed to this point, only HCl and HBr have been used. The acid HF (hydrofluoric acid) can react with alkenes, but much more slowly than the other acids mentioned before (it is a weaker acid see Chapter 2, Section 2.4). Using published values for pKg, the mineral acids can be rank ordered as to their acid strength HF (pK = 3.20) is less acidic than HCl (pKg = -2.2), which is less acidic than HBr (pK = -4.7), and HI (pKg = -5.2) is the most acidic in this series. Note the large difference in pK between HF and HCl, and remember that acetic acid (pK = 4.78 see earlier discussion) did not react with a simple alkene. HI is expected to react with alkenes rapidly, as will HBr and HCl, but the diminished acidity of HF may explain its poor reactivity in this reaction. This is not the only factor contributing to relative reactivity with alkenes, but it is a useful one for making predictions. [Pg.426]

The relative rates of hydroboration of representative heterocyclic olefins with 9-BBN have been studied [72] at temperature 25 °C, as most of the large amount of data for relative reactivities with 9-BBN is available at this temperature. These rates of reaction for heterocyclic olefins are compared with SiajBH as the hydroborating agent at 0 °C, which is described by Zweifel and Plamon-don [50]. [Pg.108]


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