Unstable compound

As discussed previously, drug absorption may be impaired or improved when food is present in the GIT. Food may reduce the rate or extent of absorption by virtue of reduced gastric-emptying rate, which is particularly important for compounds unstable in gastric fluids and for dosage forms designed to release drug... 

An allyltetrakistrifluorophosphine Ta1 compound, unstable at room temperature, has also been obtained (equation 90). Attempts to substitute all the allyl groups under higher pressure led to metallic tantalum and propane.710... 

Other compounds, unstable at RT, are prepared from TlMe3 with Ph3SnH or Et3SnH in pentane at low ... 

Periodate oxidizes Mn to [Mn04] , but, with the proper choice of conditions, Mn compounds (unstable now to oxidation rather than reduction) can be isolated. Red Na7H4Mn(I06)3 I7H2O and K7H4(I06)3 SHjO have been described, and an X-ray analysis of the former showed a tris-bidentate [Mn 06] species with Mn—O = 1.90 A. The red, insoluble compounds NaMnlO and KMnlO are isostructural with NaNilO. ... 

Alk mes have two carbon atoms joined by a tripple bond. This is highly reactive making these compounds unstable ... 

The presence of sulfur and adjacent oxygen in the seven-membered ring, 1,2-oxathiepine, makes these compounds unstable therefore, most of the known ring systems possessing this moiety are obtained in the form of the 5-oxide (sulfonate) or 5,5-dioxide (sulfonate). 

Ugi reaction 17, 809 Ullmann-Fetvadiian quinoline ring synthesis 2, 638 Unstable s. Compounds, unstable... 

Distillation boundaries always exist if there is more than one origin or terminus of residue curves in the system, which means more than one feasible bottom or top product. Typical residue curves for the system benzene-cyclohexane-acetone are shown in Figure 11.11. The most important lines are the distillation boundaries, which cannot be crossed by distillation. While the residue curves are connections between the high-boiling compound (stable node) and the low-boiling compound (unstable node), the distillation boundaries are connecting lines between the saddle point and the stable or the unstable node, respectively. 

Pol3onerization usually occurs at room temperatures and atomospheric pressure. Thermally induced side reactions are thus minimized, permitting the use and/or production of compounds unstable above room temperature. 

Bis-cyclopentadienylberyllium, obtained from BeCl and sodium cyclopen-tadienide in THF, is a very reactive compound, unstable in air and hydrolysing with violence. It sublimes under reduced pressure and decomposes at about 70°C. It has a large dipole moment (2.46 D) in benzene suggesting an unsymmetrical structure. Its proton n.m.r. spectrum, however, shows only one sharp peak from — 100° to 50°C. A single crystal X-ray diffraction study, carried out at — 120°C revealed a slip sandwich , in which one ring is symmetrically bound but the other is attached through only one carbon atom... 

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