Class I behavior

The Class I binary diagram is the simplest case (see Fig. 6a). The P—T diagram consists of a vapor—pressure curve (soHd line) for each pure component, ending at the pure component critical point. The loci of critical points for the binary mixtures (shown by the dashed curve) are continuous from the critical point of component one, C , to the critical point of component two,Cp . Additional binary mixtures that exhibit Class I behavior are CO2—/ -hexane and CO2—benzene. More compHcated behavior exists for other classes, including the appearance of upper critical solution temperature (UCST) lines, two-phase (Hquid—Hquid) immiscihility lines, and even three-phase (Hquid—Hquid—gas) immiscihility lines. More complete discussions are available (1,4,22). Additional simple binary system examples for Class III include CO2—hexadecane and CO2—H2O Class IV, CO2—nitrobenzene Class V, ethane—/ -propanol and Class VI, H2O—/ -butanol. 

For class I systems, 0 = 0 and the mixed valence absorption bands observed generally fall at frequencies larger than 27 000 cm , except when the system contains a colored ion as a constituent. Intervalence interactions (see Intervalence Transfer Transition) can provide a source for intensification of such ligand field transitions, however, in class I systems. The mixed valence electronic transition is given by equation (2), where has the same meaning for the excited state as a does for the ground state. Hence a = /J = 0 for true class I behavior. 

However, it must be acknowledged that the current BCS class boundaries are too conservative in certain aspects, which could lead to the loss of promising compounds in early development stages or prevent biowavers from being granted for drugs that exhibit Class I behavior in physiologically relevant conditions. ... 

Several classes of precursor complexes can be distinguished (see Table I), depending on the relative magnitudes of A and H g. The properties of class I systems are predominantly those of the separate components, and the electron transfer is nonadiabatic. Limiting class I behavior corresponds to the zero-interaction case discussed earlier. Class II systems possess new optical and electronic properties in addi-... 

Figure 3. Predicted DCS classification of Itraconazole (A) as well as the effect of solubility on fraction absorbed (B). The Spider plot suggest good oral bioavailability at solubility values above 100 pg/mL. The solubility of itraconazole at neutral pH is estimated at 1 ng/mL. Itraconazole can be solubilized in 2-hydroxypropyl-p-cyclodextrin to levels in excess of 10 mg/mL which suggests Class I behavior (C). (See color insert after Index.)...

Coucouvanls (Figure 1). The ion is in a site with fourfold symmetry, a square-planar environment that is often found for metal Ions with the d valence shell electronic structure of Cu . Each Cu ion is found in a site wherein the metal Ion Is bonded to three sulfur atoms. The Cu sites are all equivalent and related to each other by the fourfold symmetry of the complex. Hence the two types of copper Ions are in very different coordination environments. This is typical class I behavior since the copper ion sites are not interconvertible by symmetry. The intense blue coloration of the complex, the spectrum of which has not been completely assigned, presumably arises because of the mixed valency of... 

Fig. 6. Qualitative piessuie—tempeiatuie diagiams depicting ctitical curves for the six types of phase behaviors for binary systems, where C or Cp corresponds to pure component critical point G, vapor 1, Hquid U, upper critical end point and U, lower critical end point. Dashed curves are critical lines or phase boundaries (5). (a) Class I, the Ar—Kr system (b) Class 11, the CO2—CgH g system (c) Class 111, where the dashed lines A, B, C, and D correspond to the H2—CO, CH —H2S, He—H2, and He—CH system, respectively (d) Class IV, the CH —C H system (e) Class V, the C2H -C2H OH...

Fire Hazards - Flash Point (deg. F) (a) <0 CC (b) 0 - 73 CC (3) 73 -141 CC Flammable Limits in Air (%) Data not available Fire Extinguishing Agents Foam, carbon dioxide, dry chemical Fire Extinguishing Agents Not to be Used Water may be ineffective Special Hazards of Combustion Products Not pertinent Behavior in Fire Not pertinent Ignition Temperature Data not available Electrical Hazard Class I, Group D Burning Rate Approx. 4 mm/min. 

Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Fire Vapors may explode Ignition Temperature (deg. F) 437 Electrical Hazard Class I, Group D Bunting Rate 7.3 mm/min. 

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