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Four Extremes

All the conformations so far discussed have involved rotation about sp -sp bonds. Many studies have also been made of compounds with sp -sp bonds. " For example, propanal (or any similar molecule) has four extreme conformations, two of which are called eclipsing and the other two bisecting. For propanal the eclipsing conformations have lower energy than the other two, with P favored over Q by... [Pg.171]

The diagram below shows in graphical form the same property for alcohols. The two lines joining the four extreme values show the funnel-shaped configuration of values. It is the standard way of spotting the values of heteroscedasticity. [Pg.37]

The symptoms and signs at the Qi level are often designated as the Four Extremes, namely extremely high fever, intense thirst, heavy sweating and extremely rapid pulse. [Pg.74]

A slightly more complicated case than ethane is that of a 1,2-disubstituted ethane (YCH2—CH2Y or YCHj—CH2X),197 such as n-butane, for which there are four extremes a fully staggered conformation, called anti, trans, or antiperiplanar another staggered con-... [Pg.140]

Table 3 summarizes the results of an analysis of four extremely helium-rich luminous sdOs (Husfeld, 1986 Husfeld et al., in preparation). Here, only upper limits for the hydrogen abundances can be given as no traces of this element can be found in the spectra. Consequently, helium appears as the most abundant element. Significantly overabundant are also carbon (with one exception LSE 263) and nitrogen. Silicon is effectively unaltered. This abundance pattern compares well with the abundances found in the extreme helium stars of spectral type B (given in col. 6 of Table 3). However, it should be stressed that the carbon depletion in LSE 263 makes this star a peculiar object in its class. Table 3 summarizes the results of an analysis of four extremely helium-rich luminous sdOs (Husfeld, 1986 Husfeld et al., in preparation). Here, only upper limits for the hydrogen abundances can be given as no traces of this element can be found in the spectra. Consequently, helium appears as the most abundant element. Significantly overabundant are also carbon (with one exception LSE 263) and nitrogen. Silicon is effectively unaltered. This abundance pattern compares well with the abundances found in the extreme helium stars of spectral type B (given in col. 6 of Table 3). However, it should be stressed that the carbon depletion in LSE 263 makes this star a peculiar object in its class.
Table 3 Logarithm of mass fractions of abundant elements in four extremely helium-rich luminous sdOs, in the sun and in the Helium B stars (mean value derived from Heber, 1983). Table 3 Logarithm of mass fractions of abundant elements in four extremely helium-rich luminous sdOs, in the sun and in the Helium B stars (mean value derived from Heber, 1983).
Intramolecular charge distribution depends on the number of valence electrons and electronegativity differences. In some extreme cases it resembles the interactions, traditionally considered to define van der Waals, metallic, ionic or covalent bonding. The true interaction in all cases however, contains elements of all four extremes. [Pg.197]

There are two reasons why some radicals are more persistent than others (1) steric hindrance and (2) electronic stabilization. In the four extreme cases above, their exceptional stability is conferred by a mixture of these two effects. Before we can analyse the stability of other radicals, however, we need to look at what is known about the shape and electronic structure of radicals. [Pg.1024]

To treat the thermodynamics of addition reactions, we consider four extreme cases that differ in the degree of ionization of reactants and products (a) reactants and products are covalent (b) reactants and products are ionic (c) reactants are covalent, products ionic and (d) reactants are ionic, products covalent. The classifications a-d are also used in the subscripts (AGJ. . . AGd°) in Scheme 29. [Pg.80]

For the 1,2-disubstituted ethane, XCH2-CH2X, there are now four extreme conformers namely, antiperiplanar, anticlinal, synclinal and synperiplanar. [Pg.437]

About an sp -sp bond there are also four extreme conformers, which are divided into eclipsing and bisecting. [Pg.437]

All elements and compounds can be solidified under appropriate conditions of temperature and pressure, and the properties and structures of solids show that we must recognize four extreme types of bonding ... [Pg.6]

Although it is convenient and customary to recognize these four extreme types of bonding it should be realized that bonds of these pure types-if indeed the term pure has any clear physical or chemical meaning-are probably rather rare, particularly in the case of the first two types. Bonds of an essentially ionic type occur in salts formed from the most electropositive combined with the most electronegative elements and between, for example, the cations and the 0 atoms of the complex ion in oxy-salts such as NaNOj. Covalent bonds occur in the non-metallic elements and in compounds containing non-metals which do not differ... [Pg.6]

We have introduced the data of Table 7.2 at this point to emphasize that even the bonds in some crystalline elements cannot be described in a simple way. It appears that many bonds are intermediate in character between the four extreme types, and of these the most important in inorganic chemistry are those which are intermediate in some way between ionic and covalent bonds. [Pg.232]

Volume and location of an intravitreal injection can impact the patterns of ocular distribution and elimination. Friedrich et al. demonstrated a substantial effect of both on vitreal distribution and elimination of fluorescein and fluorescein glucuronide (252), with evaluation of four extreme positions and two injection volumes, 15 or 100 pL. The mean drug concentration remaining in the vitreous 24 hours postdose varied up to 3.8-fold with injection position, and increasing injection volume reduced this effect. [Pg.139]

Main signs symptoms Inversion counterflow of the four extremities, aversion to cold, sleeping with knees drawn up, nausea and vomiting, no thirst, abdominal pain, diarrhea, fatigued spirit, desire to sleep (all the time), a white, glossy tongue coating, and a minute, fine pulse... [Pg.83]

Main signs symptoms A faded, white facial color, a faint, lethargic voice, diminished appetite, lack of strength of the four extremities, loose stools, a pale tongue, and a fine, relaxed/retarded pulse... [Pg.90]

Avidin - an egg white protein or as a streptavidin from Streptomyces avidinii bacteria that has four extremely high-affinity-binding sites for biotin. [Pg.208]

These four extreme types of bonding can be represented on the four apexes of a tetrahedron. (See Eigure 2.)... [Pg.161]

Fig. 2.8. Memory aids for the four extreme types of bonding. Fig. 2.8. Memory aids for the four extreme types of bonding.

See other pages where Four Extremes is mentioned: [Pg.572]    [Pg.169]    [Pg.202]    [Pg.332]    [Pg.96]    [Pg.96]    [Pg.100]    [Pg.110]    [Pg.678]    [Pg.391]    [Pg.201]    [Pg.26]    [Pg.59]    [Pg.96]    [Pg.164]    [Pg.219]    [Pg.77]    [Pg.131]    [Pg.161]    [Pg.168]    [Pg.14]    [Pg.133]    [Pg.140]   
See also in sourсe #XX -- [ Pg.74 ]




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