Rules, exceptions

In the case of noncatalytic reactions, the rate of each single reaction depends, as a rule (except for too concentrated systems), only on the concentrations of the compounds undergoing chemical conversion in this reaction, and sometimes also on the concentrations of the compounds formed by the reaction... 

Tertiary halides undergo elimination most easily. Eliminations of chlorides, bromides, and iodides follow Zaitsev s rule, except for a few cases where steric effects are important (for an example, see p. 1316). Eliminations of fluorides follow Hofmann s rule (p. 1316). 

For rounding off digits in any whole number place, use the same rules, except that instead of actually dropping digits, replace them with (nonsignificant) zeros. For example,... 

Use all rules (except Rule 7) for full PK Level II assays plus Rules 2 to 6 below. 

The regiochemistry of the addition of phenylselenenyl chloride to allylic alcohols and their esters [109] can simply be rationalized by using the polarity alternation rule except in those cases where steric factors become the controlling parameters. 

This chapter draws heavily on chapter 3 of my Cement of Society (Cambridge University Press, 1989). A useful empirical survey is Robert Edgerton s Rules, Exceptions and the Social Order (Berkeley and Los Angeles, University of California Press, 1985). An alternative approach, with more emphasis on the cognitive role of norms, is Francesca Cancian s What Are Norms (Cambridge Uni-... 

If necessary, numerical subscripts are added to the labels to distinguish the non-equivalent irreducible representations which are not distinguished by the foregoing rules. Except for the fact that the totally symmetric representation (one-dimensional unit matrices) is numbered and listed first, the numbering is arbitrary and the reader is referred to Appendix I or Mulliken s report for the internationally accepted conventions. 

Molecular Collisions. In the limit as t- -oo, spin-free selection rule, except in cases of near degeneracy or very heavy atoms. Some examples of spin-free transitions are discussed in Section V. Except in the case of atom-atom collisions, point-group selection rules are seldom of importance. 

Acyclic 3, p.13 Use Systematic Names (IUPAC Rules). Exceptions Four Unsubstituted Radical Recognized by IUPAC (See Text) ... 

It is not appropriate here to comment on these new rules except that they are consistent with the competitive global marketplace which must be considered in planning industrial activities. My guess is that by the end of the decade we shall be seeing a return to longer term fundamental research in industry but in areas different from those that are now popular. But that is another story. 

For eliminations, form the carbon-carbon double bond according to Zaitsev s rule (except the Hofmann elimination) and use anti elimination to determine the stereochemistry of E2 reactions. 

Arrange the remaining electrons as lone pairs or create double or triple bonds to satisfy the octet rule. Exceptions Hydrogen satisfies the duet (two) rule, and boron and aluminum satisfy the six-electron rule. 

Because of the stronger screening In condensed media, monolayer adsorption is much more common than in gas adsorption, where the formation of multilayers is the rule, except at very low pressures. Notable exceptions are strongly associating adsorbates (like surfactants, but even with these adsorption usually remains limited to at most a bilayer) and liquid mixtures close to demlxlng conditions. 

In most of their covalent compounds, the representative elements follow the octet rule, except that hydrogen always shares only two electrons. 

The factors that determine whether or not an ionic compound will be soluble in water are complex, making predictions difficult. As a result, a series of statements or rules have come into being that guide predictions. These rules are called the solubility rules. As with most general rules, exceptions exist, but they are correct most of the time. The following rules are organized in a hierarchal structure—that is, the first rule takes precedence over the second, the second over the third, and so forth. 

The octet rule is a useful guide for most molecules with Period 2 central atoms, but not for every one. Also, many molecules have central atoms from higher periods. As you ll see, some central atoms have fewer than eight electrons around them, and others have more. The most significant octet rule exceptions are for molecules containing electron-deficient atoms, odd-electron atoms, and especially atoms with expanded valence shells. 

SAMPLE PROBLEM 10.5 Writing Lewis Structures for Octet-Rule Exceptions Problem Write Lewis structures for (a) H3PO4 (pick the most likely structure) (b) BFCI2. Plan We write each Lewis structure and examine it for exceptions to the octet rule. In (a), the central atom is P, which is in Period 3, so it can use d orbitals to have more than an octet. Therefore, we can write more than one Lewis structure. We use formal charges to decide if one resonance form is more important. In (b), the central atom is B, which can have fewer than an octet of electrons. 

These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception ... 

He and H cannot serve as central atoms in a Lewis structure. Both can have no more than two valence electrons. Fluorine needs only one electron to complete its valence level, and it does not have d orbitals available to expand its valence level. Thus, it can bond to only one other atom. 10.3 All the structures obey the octet rule except c and g. 

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