Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Substitution hierarchy

The GIAO-MP2/TZP calculated 13C NMR chemical shifts of the cyclopropylidene substituted dienyl cation 27 show for almost all carbon positions larger deviations from the experimental shifts than the other cations 22-26. The GIAO-MP2/TZP method overestimates the influence of cr-delocalization of the positive charge into the cyclopropane subunit on the chemical shifts. Electron correlation corrections for cyclopropylidenemethyl cations such as 27 and 28 are too large to be adequately described by the GIAO-MP2 perturbation theory method and higher hierarchies of approximations such as coupled cluster models are required to rectify the problem. [Pg.137]

The authors find lastly that expression (A.25) substituted in formula (A.31) of the Prigogine theory leads to a result equivalent to the one that one obtains if one combines Eqs. (A. 17-23) with the first equation of the hierarchy (6) in the Bogolubov method. [Pg.373]

Notice that the add(), get(), remove(), and getIterator() methods do nothing but throw UnsupportedOperationException. This is because these operations are not available in the leaf objects in the composite hierarchy such as ChemicalSample. They only make sense in the composite objects such as ChemicalLibrary. Defining these methods in the component class makes the design compliant with The Liskov Substitution Principle (Martin, 2003). [Pg.105]

Because flO+flfIt = the operator flftt is the projection onto the scattering states. Substituting the solution (3.12) into the first equation of the hierarchy, we obtain the modified Boltzmann equation... [Pg.202]

The cooperative nature of two similar or different meta-related DMG enables DoM at the in-between site thus constituting a different route to continuous 1,2,3-substitution patterns (7) [9]. The analogous meta and para-related DMG isomers provide routes, most of which have not been tested, to other patterns which are a function of their relative hierarchy qualitatively established by inter-or intramolecular competition experiments (Scheme 3) [5],... [Pg.108]

For a molecule without symmetry reduction the sum-over-states expression for the hyperpolarizability yean often be modeled within the three level approximation (the ground state (index 0) and two excited states (indices 1,2 - not necessarily indicating the hierarchy of the energy eigenvalues)). If we assume po2 Poll f°r substituted molecules with a centrosymmetric backbone as described above, the number of terms reduces leaving only three terms to consider the negative term N > the dipolar term D , and the two-photon term TP, which includes the second excited state 2Ag. In the static limit one obtains for a one-dimensionally conjugated molecule... [Pg.162]

Having substituted Eq. (27) into the second equation of the BBGKY hierarchy at equilibrium [Eq. (23)], we arrived at... [Pg.455]

The designation of central atom and ligands, generally straightforward in mononuclear complexes, is more difficult in polynuclear compounds where there are several central atoms in the compound to be named, e.g. in polynuclear coordination compounds, and chain and ring compounds. In each case, a priority order or hierarchy has to be established. A hierarchy of functional groups is an established feature of substitutive nomenclature Table VI shows an element sequence used in compositional and additive nomenclature. [Pg.17]

Substituting Eq. (267) into Eq. (265), taking the inner product, and utilizing the orthogonal properties and known recurrence relations [51] for the associated Legendre functions Pf cosi ) and the Hermite polynomials H (z) then yields the infinite hierarchy of differential recurrence relations for the clnm(t) governing the orientational relaxation of the system, namely,... [Pg.382]

In order to get some insight on how ELF works, we will analyse a number of parent molecules CeHsX (X = H, OH, F, Cl, Br and I). Their localization domains are displayed in Figure 14. Except for the substituent itself, all these molecules have 6 V(C, C), 5 V(C, H) and one V(C, X) basins. The differences are to be found in the hierarchy of the V(C, C) basins which is ruled by the nature of the substituent. In benzene, all the V(C, C) basins are equivalent and therefore the six critical points of index 1 between these basins have the same value, i.e. rj(rc) = 0.659. In the phenyl halides where the molecular symmetry is lowered from D h to C2v, the former critical points are then distributed in four sets according to the common carbon position ipso, ortho, meta and para. In phenol with a Cj symmetry, the two ortho and the two meta positions are not totally equivalent. In all studied molecules, the r) rc) values are enhanced in the ipso, ortho and para positions and decreased in the meta position. It has been remarked that the electrophilic substitution sites correspond to the carbon for which r) rc) is enhanced. Moreover, it is worthwhile to introduce electrophilic substitution positional indices defined by equation 26,... [Pg.71]

Notwithstanding the fact on whether or not a work area is exempted ftom exposure measurements, other obligations of the employer according to the Ordinance of Hazardous Susbstances remain in force like its obligation to use less hazardous substitutes if available, to respect the hierarchy of protective measures, to eqip every workplace with an operating instructions and to perform regular trainings for the workforce. [Pg.206]

The substitution of the expansion in Eq. (9) into the kinetie equation, Eq. (8), leads after several intermediate rearrangements to an analogous expansion in Legendre polynomials of the entire kinetie equation and, because of the orthogonality of the polynomials, ultimately to a hierarchy of equations (Shkar-ofsky et al., 1966 Golant et al, 1980). This equation system includes the expansion coefficients z, t), and its approximate solution finally yields these coefficients and thus the velocity distribution. [Pg.28]

DOE O 440.1A, sec. 4(j)(4). 29CFR1910.120(g)(l) 29CFR1910.134(a) 29CFR1910.1450(i) 4.1.1.3 Hazard controls shall be selected using the following hierarchy (1) Elimination of the hazard through practices such as chemical substitution or process modification (2) Engineering controls (3) Work practices and administrative controls and (4) Personal protective equipment... [Pg.207]

With the workplace hazards identified and defined, the next logical step is to eliminate or control them. Historically, there have been two predominant concepts about hazard controls. The first concept is to think of hazard control as a hierarchy of methods of control. In the hierarchy, the best control method is to eliminate the hazard through redesign or substitution. If elimination or substitution cannot be achieved, then the next-best approach is to block employee access to the hazard. Fintilly, if blocking cannot be achieved, then a last approach would be to warn the employees of the hazard and train them how to avoid the hazard. [Pg.1175]

However, this has led to a substitution of PPE for safety itself, a consequence at direct odds with accepted risk assessment philosophy. Whichever hierarchy of risk reduction is utilised, PPE is always near the bottom in terms of a risk reduction strategy, if not actually in last place. The Health and Safety Executive (2003) states that PPE should be the last resort in health and safety management, yet its visibility and prominence within the construction site environment has led to a social construction of safety so tightly interwoven with PPE that the two are rarely separated. Although PPE is certainly an artefact of safety, it is not safety itself, and it is important that this distinction should be explored to ensure it is better understood. [Pg.66]

Substitution of this expansion into (4.16) yields the hierarchy of ordinary differential equations ... [Pg.129]

Behavior-based safety places responsibilities on workers for which they may not be qualified. Although worker involvement is important, it has limitations and is not a substitute for technically competent health and safety experts reviewing both existing and future operations to insure that hazards are identified and controlled. Few workers have been trained in hazard identification, risk evaluation or methods of control (hierarchy) [p. 17]. [Pg.429]

A major point which has been reiterated in many sections of this paper is that the comparison of closely related species is critical to the understanding of the evolution of nucleotide sequences. In such comparisons it is immediately obvious what changes occur first and what biases are present. It is only then, through comparisons of taxa from a hierarchy of divergence levels, that the masking effect of multiple substitutions can be sorted out and more accurate evolutionary trees can be constructed. [Pg.61]


See other pages where Substitution hierarchy is mentioned: [Pg.350]    [Pg.49]    [Pg.174]    [Pg.300]    [Pg.407]    [Pg.275]    [Pg.12]    [Pg.768]    [Pg.453]    [Pg.224]    [Pg.282]    [Pg.288]    [Pg.17]    [Pg.33]    [Pg.90]    [Pg.16]    [Pg.420]    [Pg.114]    [Pg.119]    [Pg.281]    [Pg.118]    [Pg.288]    [Pg.4]    [Pg.145]    [Pg.252]    [Pg.458]    [Pg.32]    [Pg.360]    [Pg.465]    [Pg.22]    [Pg.270]   


SEARCH



Hierarchy

© 2024 chempedia.info