Factor entries

Approximately 3,500 structures were removed because of missing atoms (usually H) in the coordinate sets, atoms with incorrect valences (usually H with 0 or more than one bond) and bad bond angles. Finally, duplicate structures were removed to leave just the lowest R-factor entry. The space groups included in the analysis are given in Table 2. 

Unsubstituted and o/ -substituted substrates (entries 1-3) give the expected products in good yields. The reader will have noticed that examples in entries 5-9 were chosen to study the regioselectivity of the rearrangement. It was found to be excellent with the exception of 2-naphthalene substituted substrate (entry 9). In the other cases, electronic (entries 5 and 6) or steric factors (entry 7) govern at which position the carbanion is more likely to be formed. 

However, an additional lesson was learned from the computer run sent to this author that included data on several hundred injuries. Detail entered into the computer system on each incident was extensive. But, it allowed only one causal factor entry, the instruction for which was Enter the unsafe act code. Unwittingly, the system encouraged an unwanted focus on the unsafe act of the worker. The data entry system was revised. 

The sexlic bending term is a scale factor ST times the t iiadratic bending term. This constant SPcan be set to an arbitrary value by an entry m the Registry or the chem.ini file. The default value for MM+ is SP= 7.0 X 10 . The constant 0.043828 converts the MM-r... 

The extreme influence water can exert on the Diels-Alder reaction was rediscovered by Breslow in 1980, much by coincidence . Whale studying the effect of p-cyclodextrin on the rate of a Diels-Alder reaction in water, accidentally, the addition of the cyclodextrin was omitted, but still rate constants were observed that were one to two orders of magnitude larger than those obtained in organic solvents. The investigations that followed this remarkable observation showed that the acceleration of Diels-Alder reactions by water is a general phenomenon. Table 1.2 contains a selection from the multitude of Diels-Alder reactions in aqueous media that have been studied Note that the rate enhancements induced by water can amount up to a factor 12,800 compared to organic solvents (entry 1 in Table 1.2). 

The regioselectivity of the reaction appears to be determined by a balance of electronic and steric factors. For acrylate and propiolate esters, the carb-oxylate group is found preferentially at C3 of the carbazole product[6-8]. Interestingly, a 4-methyl substituent seems to reinforce the preference for the EW group to appear at C3 (compare Entries 4 and 5 in Table 16.2). For disubstituted acetylenic dicnophiles, there is a preference for the EW group to be at C2 of the carbazole ring[6]. This is reinforced by additional steric bulk in the other substituent[6,9]. 

The functional form for van der Waals interactions in AMBER is identical with that shown in equation (13) on page 175. The coefficients A. and B.. are computed from the parameters in the file pointed to by the 6-12AtomVDW entry for the parameter set in the Registry or the chem. ini file, usually called nbd.txt(dbf), and optionally with the file pointed to by the 6-12PairVDW entry for the parameter set, usually called npr.txt(dbf). The standard AMBER parameter sets use equations (15) and (16) for the combination rules by setting the 6-12AtomVDWFormat entry to RStarEpsilon. The 1 van der Waals interactions are usually scaled in AMBER to half their nominal value (a scale factor of 0.5 in the Force Field Options dialog box). 

Section 2 combines the former separate section on Mathematics with the material involving General Information and Conversion Tables. The fundamental physical constants reflect values recommended in 1986. Physical and chemical symbols and definitions have undergone extensive revision and expansion. Presented in 14 categories, the entries follow recommendations published in 1988 by the lUPAC. The table of abbreviations and standard letter symbols provides, in a sense, an alphabetical index to the foregoing tables. The table of conversion factors has been modified in view of recent data and inclusion of SI units cross-entries for archaic or unusual entries have been curtailed. 

Health and Safety Factors. Magnesium hydroxide is not absorbed by the skin. Dry magnesium hydroxide may irritate the eyes, skin, nasal passages, and respiratory tract. Routes of body entry are skin contact, eye contact, inhalation, and ingestion. No LD q values for Mg(OH)2 are available. 

AH of these factors should be considered when evaluating the quaUty of laboratory notebook entries. These entries may otherwise never be considered until they are the subject of a legal contest, at which time quaUty review may be too late. 

Database Records. From 1975 through 1991, database records increased from 52 million to 4.06 biUion, a factor of 77, and the number of databases grew from 301 to 7637, a factor of 24. Database entries grew from 301 to 6261, a factor of 20. The number of producers continues to grow somewhat more slowly in part because individual producers create multiple databases. There were 2372 producers in 1991 and the average producer... 

Electrical. The plant electrical system is sometimes more important than the steam system. The electrical system consists of the utihty company s entry substation, any ia-plant generating equipment, primary distribution feeders, secondary substations and transformers, final distribution cables, and various items of switch-gear, protective relays, motor starters, motors, lighting control panels, and capacitors to adjust power factor. 

The expander design will be of axial entry (Figure 5-14), overhung rotor, stiff shaft construction with one or two rows of blading designed and constructed for 100,000 hrs of life and at least 3 yrs of uninterrupted continuous service. It is recognized that uninterrupted operation for this period of time involves factors beyond the Seller s control. 

Entry 3 has only alkyl substituents and yet has a significant lifetime in the absence of oxygen. The tris(/-butyl)methyl radical has an even longer lifetime, with a half-life of about 20 min at 25°C. The steric hindrance provided by the /-butyl substituents greatly retards the rates of dimerization and disproportionation of these radicals. They remain highly reactive toward oxygen, however. The term persistent radicals is used to describe these species, because their extended lifetimes have more to do with kinetic factors than with inherent stability." Entry 5 is a sterically hindered perfluorinated radical and is even more long-lived than similar alkyl radicals. 

The calculation of the pressure drop for a chosen exhaust depends on the calculation method (Chapter 9). Pressure drop is usually calculated as the product of a hood entry loss factor, and the dynamic pressure in the connecting duct, p,/. The is expressed a.s p v-/l, where p is the air density and 1/ IS the air velocity in the duct. Some common hood entry loss factors are given in Table 10.4. 

TABLE 10.4 Entry Loss Factors for Flangod or Unflanged Round, Square, and Rectangular Tapered Openings... 

Exhaust shape Hood entry loss factor... 

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