Temperature substitution

A great variety of differently substituted pteridine derivatives have been synthesized starting from (109) or the 2,4,6,7-tetrabromo compound (60USP2940972), which shows a corresponding reactivity pattern. Amines at low temperature substitute only the 6- and... 

If the gas samples are at the same temperature, substitution of Eq. (43) for the intensity of collisions gives... 

In a CO matrix, therefore, the primary product involves an expanded coordination nunber ("ring-slippage") and it is argued that such a species is consistent with the associative mechanism proposed for room temperature substitution reactions of (13 -05115)Co-... 

If we assume that the entropy and enthalpy are relatively independent of temperature, we can drop the subscript m on temperature in Eq. (3.32), thereby obtaining a more general relationship between the entropy and enthalpy of fusion as a function of temperature. Substitution of this modified form of Eq. (3.32) into Eq. (3.31) gives the following relation for the free energy ... 

For a dilute miscible blend containing P2VN, we have shown that Qd/Qm = 0.55 0.15 and that q 2q = 0.026 at room temperature. Substitution of these values into Eq. (1) along with the no-transfer expression for M, yields [Pg.67]

The integral of the heat release rate with respect to temperature is taken over the entire region in which the reaction rate is non-zero. In fact, due to the rapid decrease in the reaction rate as the temperature falls, the basic contribution to the integral is made by a comparatively narrow temperature interval adjacent to the combustion temperature. Substituting the appropriate law for the reaction rate (mono- or bimolecular, etc.), we obtain the corresponding, rather cumbersome expressions for the flame velocity which we do not give here. The basic formula (1.3.5) allows us to analyze the influence of various parameters of the mixture on the velocity. 

Using the superscript sc to refer to the transition from crystalline solid to supercooled liquid at a constant temperature, substituting... 

Bazhulina and Morozov (137) have investiaged the equilibrium constants between various ions and the tautomeric forms of vitamin Bg together with the effect of temperature, substitution, and medium on the absorption properties of these forms. The experimental spectroscopic data are in good agreement with quantum calculation. 

Above C5 (aliphatic) Apiezon phases carbowax 1500, 1540, 4000, 6000, 20M most of the high-temperature substituted adipates, phthalates, succinates, and sebacates (boiling point separations) methyl silicones... 

Measurements of temperature and concentration in CO-H2-CH4 (or natural gas) flames were carried out. Rate profiles were developed for two excess air and two slightly fuel-rich flames as a function of temperature. Substitution of natural gas for methane does not bring about a marked change in the overall reactivity of these systems. Application of a modified theory analysis to these multiple-fuel flame mixtures allows one to satisfactorily correlate calculated values of the burning velocity with measured values. 

It is noteworthy that in this latter reaction no exchange of boron atoms between HjBfpzjjBHj and the BXj occurs, as was demonstrated by employing boron-10 labelled boron tribromide Hence, the central B2N4 ring of the pyrazabole apparently is not opened during the course of this low-temperature substitution process. 

The prototype of this class, OP(NH2)3, is formed in the reaction of OPCI3 with liquid ammonia orwith gaseous NH3 in trichloromethane solution at low temperature. Substituted phosphoric acid triamides 0=P(NR2)3 are prepared in the reaction of phosphoras oxotrichloride with secondary amines, under heating or in the presence of acid scavengers under milder conditions the mono- and diamido chlorides can be easily obtained (equation 6). Hexamethylphosphoric acid triamide, OP(NMc2)3, an excellent aprotic organic solvent prepared from OPCI3 and dimethylamine, deserves to be mentioned here. ... 

The colour of ICPs can also be sensitive to temperature. Substituted polythiophenes, in particular, show a marked blue shift of the highest wavelength absorption band when films or solutions are heated [7-9]. These reversible colour changes have been attributed to a twisting of the polymer backbone to a less ordered non-planar conformation. Less dramatic thermochromic effects have also been reported for polyanilines [3,10,11] where circular dichroism studies of... 

High temperature substitutive chlorination of olefins, leading to synthetic glycerol and to new intermediates for the plastics industry (discovered in America, 1935 to 1939). 

R = CH3) is small, and so also is the effect of silyl183. The calculated barriers are 42.2 kcal mol -1 in H2C=SiH2, 43.5 kcal mol"1 in H2C=SiH(CH3) and 42.8 kcal mol -1 in H2C=SiH(SiH3), all at the MP3/6-31G //6-31G level of theory183. The barriers may be smaller with substituents such as OH, which stabilize the silylene strongly, thus making equation 18 more exothermic. However, the isomerization barriers are still expected to be substantial so that at low temperatures substituted silenes are predicted to be kinetically stable towards 1,2-hydrogen shifts. Systematic studies on the effect of substituents on these isomerization barriers are needed for more quantitative estimations. 

---