Unspecified bond

Cyclo-(Gly2-His[Pg.46]

A summary of addition reactions of alkenes with 1-methylcyclopentene as the organic substrate. A bond designated means that the stereochemistry of the group is unspecified. For brevity the structure of only one enantiomer of the product is shown, even though racemic mixtures would be produced in all instances in which the product is chiral. 

Porschke and colleagues have observed a curious isomerization of the complex Pd(dippe) 2 / i- 7 / -HC2C2H in dg-thf solution at —80°C. Over a period of about a week both Pd(dippe) moieties become coordinated to the same C C bond. Warming a solution of this lower symmetry isomer to 0°C results in only partial reversal of the isomerization. The isomers are apparently in slow equilibrium, with various subtle and unspecified factors determining which one is preferred and while the Pd(dippe) 2 Ai- M- -HC2C2H (68) form is thermodynamically favored in solution, crystallization affords Pd(dippe) 2 /z-/7 >7 -HC2CsCH (69) (Scheme 19). ... 

In cases where there are no electronically driven distortions, the orbital description provides no better account of the chemistry than the bond valence model. Rather it tends to make an essentially simple situation more complex. For example, consider the phosphate and nitrate anions, and NOJ. In orbital models the P atom is described as sp hybridized and the N atom as sp hybridized, but these descriptions are just representations of the spherical and cylindrical harmonics appropriate to the observed geometries. They provide no explanation for why P is four but not three coordinate, or why N is three but not four coordinate. The bond valence account given in Chapter 6 is simpler, more physical, and more predictive. The orbital description is merely a rather complicated way of saying that the ions obey the principle of maximum symmetry but implying that the constraints are related in some unspecified way to the properties of one-electron orbitals rather than to the ionic sizes. 

NS 5%(suitable for ignition rather than for detonation) and b)K chlorate 55 Pb thiocyanate 45% E)Colored smokes K chlorate 22-33, dye 30-50, Na or K bicarbonate 3-10, confectioner s sugar or lactose 20-35, kerosene or paraffin oil 2-4, kieselguhr 0-4 red iron oxide 0-3% F) Plastic Bonded colored smoke K chlorate 23, dye 51, sugar 18 K bicarbonate 8% combined with 2.2 parts of polyvinyl acetate plasticized by dichloro-methane and dried by evapn G) Cap mixtures a)K chlorate 67, red P 27, S 3 pptd Ca carbonate 3%, bound with unspecified amt of gum water and b)K chlorate 61, red P 4, black Sb sulfide 21,pptd Ca carbonate 2 animal glue 12% H)Railroad torpedo K chlorate 40, S 16, sand(60 mesh) 37, binder 5 8r neutralizer 2% I)Whistling compns K chlorate 73-77, gallic acid 24-19 red gum 3-4%(Ref 26,pp 270-80)... 

According to this simple picture, beryllium hydride should have two different types of H-Be bonds —one as in 1 and the other as in 2. This is intuitively unreasonable for such a simple compound. Furthermore, the H-Be-H bond angle is unspecified by this picture because the 2s Be orbital is spherically symmetrical and could form bonds equally well in any direction. 

A Perkin-Elmer MPF-2A Fluorescence Spectrophotometer was used to determine the excitation and emission wavelengths required for achieving maximum fluorescence intensity for the pesticides studied. The MPF-2A contained a 150 watt xenon arc and an excitation monochromator with a grating blazed at 300 nm as the excitation unit a Hamamatsu R 777 photomultiplier tube (sensitivity range 185 - 850 nm) and an emission monochromator grating blazed at 300 nm as the emission detection unit. A DuPont Model 848 Liquid Chromatograph was used for HPLC (Figure 2). The accessory injection device included a Rheodyne Model 70-10 six-port sample injection valve fitted with a 20 y liter sample loop. A Whatman HPLC column 4.6 mm x 25 cm that contained Partisil PXS 1025 PAC (a bonded cyano-amino polar phase unspecified by the manufacturer) was used with various mobile phases at ambient temperature and a flowrate of 1.25 ml/minute. 

Despite the completely different approach to chemical interaction, which has been followed here, the conventional standard symbols which are used to define the connectivity in covalent molecules, can also be applied, without modification, to distinguish between interactions of different order. However, each linkage pictured by formulae such as H3C-CH3, H2C=CH2, HC=CH, represents the sharing of a single pair of electrons with location unspecified. The number of connecting fines only counts bond order and may be established from the classical valence rules, e.g. v(C,N,0,F)=(4,3,2,l). Special symbols are used for non-integral bond orders, as in the symbol for benzene ... 

Lumefantrine contains two stereogenic units, i.e., a Z-configured double bond and a chirality centre whose configuration in the formula given is unspecified. As a result the formula represents two compounds (enantiomers) with R,Z and S,Z configuration, respectively. Both are present in the racemic pharmaceutical. There are formally 22 = 4 isomers possible with this constitution in addition to the isomers of lumefantrine there are also two others with an E-configured double bond. 

This wavy line indicates a bond of unspecified stereochemistry. 

A special cyclodextrin bonded phase, with an appropriate binder, has been used in TLC plates to separate isomers, including optical isomers.45 Another type of TLC plate made by Macherey-Nagel uses a reverse phase bonded layer with Cu2+ ions and an unspecified chiral reagent. 

The structural data from which the structure of vinoxine (89) was deduced have been described in greater detail.65 The configuration at C-16 is based on the closer resemblance of the XH n.m.r. spectrum of vinoxine to that of 16-epipleiocarpamine rather than that of pleiocarpamine. In reference 65, for some unspecified reason, the configuration given for the double bond is different from that illustrated in (89) and postulated in the earlier communication 334 however, the similarity of the chemical shifts of the protons of the ethylidene group with the corresponding ones in the pleiocarpamine series makes it extremely probable that the configuration about the double bond [i.e. (Ij)] is the same in all these alkaloids. 

Incorporation of alpha bonds directly into the nomenclature allows various isomorphisms to be more accurately described. For example [14], hydrogen fluoride in the solid (and probably in the liquid) state consists of a long (unspecified length) chain of hydrogen bonded H-F molecules in a zig-zag (/HFH = 120.1°) chain. This would be nomenclated as ... 

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