Vaporization sublimation

In solution, benzotriazole also exists almost exclusively as the IH tautomer 25a,c. This conclusion was drawn on the basis of early NMR [69T4667 76AHC(Sl),p. 295] and NNMR (82JOC5132 97MRC35) spectral studies and confirmed by measurements of enthalpies of solution, vaporization, sublimation, and solvation in water, methanol, and DMSO (89JA7348). 

Benzotriazole can exist in two tautomeric forms, l-//-benzotriazole (6.46, R = H) and 2-/f-benzotriazole. If the aromatic ring contains a substituent, the 1- and 3-nitrogen atoms of the triazole are not equivalent, and therefore a 3-//-benzotri-azole derivative can also exist. The equilibrium between the 1 -H and 2-H tautomers of benzotriazoles is strongly on the side of the 1 -H tautomer, in contrast to triazole where the 2-H tautomer is dominant. Tomas et al. (1989) compared experimental data (enthalpies of solution, vaporization, sublimation, and solvation in water, methanol, and dimethylsulfoxide) with the results of ab initio theoretical calculations at the 6-31G level. 

The terms enthalpy of fusion, enthalpy of vaporization, enthalpy of combustion, and many more cause some students to believe that there are many different kinds of enthalpies. There are not. These names merely identify the processes with which the enthalpy term is associated. Thus, there are processes called fusion (melting), vaporization, sublimation, combustion, and so forth. The corresponding enthalpy changes are called by names that include these descriptions. 

The quantities defined by Eqs. (2)—(7) plus Vs max, Vs min, and the positive and negative areas, A and, enable detailed characterization of the electrostatic potential on a molecular surface. Over the past ten years, we have shown that subsets of these quantities can be used to represent analytically a variety of liquid-, solid-, and solution-phase properties that depend on noncovalent interactions [14-17, 84] these include boiling points and critical constants, heats of vaporization, sublimation and fusion, solubilities and solvation energies, partition coefficients, diffusion constants, viscosities, surface tensions, and liquid and crystal densities. 

These energies relate to bond rearrangement in gaseous molecules, but calculations are often performed for reactions of condensed phases, by combining the enthalpies of vaporization, sublimation, etc. We can calculate a value without further correction if a crude value of AHr is sufficient, or we do not know the enthalpies of phase changes. 

Calculations at the 6-3IG level indicate that in the gas phase, 2//-l,2,3-triazole is more stable than 1//-1,2,3-triazole by about 4.5 kcal moC. In solution, the IH isomer becomes the more stable species because the large difference in dipole moments favors the more polar tautomer. The triazolium ion (75) is predicted to be more stable than (76) by about 13.5 kcal mol <89Mi40i-0i>. 2//-1,2,3-Triazole represents more than 99.9% of the equilibrium mixture in the gas phase. However, the ab initio calculated proton affinity of 1//-benzotriazole is 10.2 kcal mol larger than that of 2//-benzotriazole, which is consistent with ICR measurements (1-methylbenzotriazole is 10 kcal mol more basic than 2-methylbenzotriazole). Measurements of enthalpies of solution, vaporization, sublimation and solvation in water, methanol and DMSO confirm the predominance of the IH tautomer in solution <89JA7348>. The energy difference between the tautomers of 1,2,3-triazole has also been estimated at the 6-31G (MP2)//3-21G level including zero-point effects. The... 

The heat capacity, Cp, a useful parameter in evaluating vaporization, sublimation, and fusion enthalpies with temperature, was determined by DSC measurements for 1,3-oxathiane 3,3-dioxide to be 148.1 2.6 J moC at... 

The symbols given in this book for the various heats of reaction, fusion, vaporization, sublimation, transition, dissociation, and formation are merely abbreviations used for convenience in the present work, and are not proposed to be used in lieu of, or in connection with, the regularly accepted symbols of chemical thermodynamics. 

A water vapor flow from the chamber to the condenser larger than the vapor sublimed from the ice. 

Photodissociation of larger ions (>200 daltons) formed by electron impact was also studied. These ions were produced by electron ionization of vapor sublimed from the standard heated solids insertion probe. Probe temperatures of 150-200 C were... 

Indeed, we see in the world only water, more or less condensed. Between the heavens and the earth, all is smoke, mist, vapors, pressed from the center, the interior of the earth, and elevated above its circumference in the part which we call air. The weakness of the organs of our senses does not permit us to see the subtle vapors, or emanations of celestial bodies, which we call influences, and which mingle with the vapors sublimating from sub-lunar bodies. The eyes of the mind must aid the weakness of the eyes of the body. 

Phase equilibria of vaporization, sublimation, melting, extraction, adsorption, etc. can also be represented by the methods of this section within the accuracy of the expressions for the chemical potentials. One simply treats the phase transition as if it were an equilibrium reaction step and enlarges the list of species so that each member has a designated phase. Thus, if Ai and A2 denote liquid and gaseous species i, respectively, the vaporization of Ai can be represented stoichiometrically as —Aj + A2 = 0 then Eq. (2.3-17) provides a vapor pressure equation for species i. The same can be done for fusion and sublimation equilibria and for solubilities in ideal solutions. 

Endothermic Fusion Vaporization Sublimation Desorption Desolvation Melting of drug substances purity evaluations Evaporation of liquid or semisolid excipients Removal of frozen water during lyophilization Drying of wet granulated formulations Removal of stoichiometric water from crystalline hydrates... 

Solid iodine is converted directly to a vapor (sublimes) when warmed. Here, purple iodine vapor is redeposited as a solid on the cooler upper surfaces of the vessel. 

Fusion = fus (solid to liquid) vaporization = vap (liquid to vapor) sublimation = sub (solid to vapor) -> Solid-to-solid phase changes for example, Sn(gray) Sn(white)... 

Several properties have been estimated by the GIPF approach such as heat of vaporization, sublimation [Politzer, Murray et al, 1997] and fusion [Murray, Brinck et al, 1996], boiling point and critical constants [Murray, Lane et al, 1993a], surface tension, liquid and solid density [Murray, Brinck et al, 1996], crystal lattice energy [Politzer and Murray, 1998], impact sensitivity [Murray, Lane et al, 1998], diffusion coefficient [Politzer, Murray et al, 1996],... 

Some solid substances can change to the gaseous state directly, without melting first. The process by which particles of a solid escape from its surface and form a gas is called sublimation. For example, dry ice, solid carbon dioxide, does not melt but sublimes. Ice also sublimes. Some molecules in ice leave the surface and become water vapor. Sublimation of ice is the reason that food stored for a long time in a freezer becomes freezer burned. 

Vaporization Sublimation Fusion Aerosols Nucleation The changing of a solid or a liquid to the vapor state. The changing of a solid to the vapor state. The changing of a solid to the liquid state. Liquid droplets or solid particles dispersed throughout a gas. The formation of particles in a supersaturated vapor (or in the air). 

In addition to water vapor, sublimed magnesium phthalocyanine also... 

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