More Molecules

Fig. 12.9 A distance map indicates the distances available to specified groups. As more molecules are considered, the permitted regions get smaller.

FIGURE 3 5 Distribution of energies (a) The number of molecules with energy greater than fact st temper ature T, is shown as the darker green shaded area (b) At some higher tempera ture T2 the curve is flatter and more molecules have energies in excess of fact... 

Steps 2-4 The alkoxyborohydnde formed m the first step contains three more hydrogens that can be donated to carbonyl groups It reacts with three more molecules of the starting aldehyde or ketone... 

Steps 6-8 Three more hydrolysis steps convert the tnalkoxyborate to three more molecules of R2CHO and ( 0)4B-... 

Linear polyethers derived from three or more molecules of aliphatic dihydroxy compounds, particularly when the chain length exceeds ten units, are most conveniently named by open-chain replacement nomenclature. For example, CH3CH2—O—CH2CH2—O—CH2CH3 could be 3,6-dioxaoctane or (2-ethoxy)ethoxyethane. 

If the temperature were raised, more molecules would attain the excited state, but even at 50,000°C there would be only one excited-state atom for every two ground-state atoms, and stimulated emission would not produce a large cascade effect. To reach the excess of stimulated emissions needed to build a large cascade (lasing), the population of excited-state molecules must exceed that of the ground state, preferably at normal ambient temperatures. This situation of an excess of excited-state over ground-state molecules is called a population inversion in order to contrast it with normal ground-state conditions. 

Cluster ion. An ion formed by the combination of two or more molecules of a chemical species, often in association, with a second species. For example, ((HjO) ) is a cluster ion. 

Molecular Nature of Steam. The molecular stmcture of steam is not as weU known as that of ice or water. During the water—steam phase change, rotation of molecules and vibration of atoms within the water molecules do not change considerably, but translation movement increases, accounting for the volume increase when water is evaporated at subcritical pressures. There are indications that even in the steam phase some H2O molecules are associated in small clusters of two or more molecules (4). Values for the dimerization enthalpy and entropy of water have been deterrnined from measurements of the pressure dependence of the thermal conductivity of water vapor at 358—386 K (85—112°C) and 13.3—133.3 kPa (100—1000 torr). These measurements yield the estimated upper limits of equiUbrium constants, for cluster formation in steam, where n is the number of molecules in a cluster. 

Condensa.tlon, This term covers all processes, not previously iacluded ia other process definitions, where water or hydrogen chloride is eliminated ia a reaction involving the combination of two or more molecules. The important condensation reactions are nitrogen and sulfur heterocycle formation, amide formation from acid chlorides, formation of substituted diphenyl amines, and misceUaneous cyclizations. 

We showed that these mesoporous silica materials, with variable pore sizes and susceptible surface areas for functionalization, can be utilized as good separation devices and immobilization for biomolecules, where the ones are sequestered and released depending on their size and charge, within the channels. Mesoporous silica with large-pore-size stmctures, are best suited for this purpose, since more molecules can be immobilized and the large porosity of the materials provide better access for the substrates to the immobilized molecules. The mechanism of bimolecular adsorption in the mesopore channels was suggested to be ionic interaction. On the first stage on the way of creation of chemical sensors on the basis of functionalized mesoporous silica materials for selective determination of herbicide in an environment was conducted research of sorption activity number of such materials in relation to 2,4-D. 

In the second step, the spatial restraints and the CHARMM22 force field tenns enforcing proper stereochemistry [80,81] are combined into an objective function. The general form of the objective function is similar to that in molecular dynamics programs such as CHARMM22 [80]. The objective function depends on the Cartesian coordinates of —10,000 atoms (3D points) that form a system (one or more molecules) ... 

Chemical reaction whereby two or more molecules combine and separate out water or other substance. When polymers are formed, it is referred to as polycondensation. 

Condensation Chemical reaction whereby two or more molecules com-... 

A gas-processing plant, as described in Chapter 9, is designed to recover ethane, propane, butane, and other natural gas liquids from the gas stream. A condensate stabilizer also recovers some portion of these liquids. The colder the temperature of the gas leaving the overhead condenser in a reflux stabilizer, or the colder the feed stream in a cold-feed stabilizer, and the higher the pressure in the tower, the greater the recovery of these components as liquids. Indeed, any stabilization process that leads to recovery of more molecules in the final liquid product is removing those molecules from the gas stream. In this sense, a stabilizer may be considered as a simple form of a gas-processing plant. 

Stimulation of glycogen breakdown involves consumption of molecules of ATP at three different steps in the hormone-sensitive adenylyl cyclase cascade (Figure 15.19). Note that the cascade mechanism is a means of chemical amplification, because the binding of just a few molecules of epinephrine or glucagon results in the synthesis of many molecules of cyclic / MP, which, through the action of c/ MP-dependent protein kinase, can activate many more molecules of phosphorylase kinase and even more molecules of phosphorylase. For example, an extracellular level of 10 to 10 M epinephrine prompts the for-... 

The dependence of the velocity of a reactioii on concentration follows from the fact that the fortes betw n the molecules are of short range so that reaction will take plac only when the reactant molecules are almost in contact. Thus collision of two (or more) molecules must occur for reaction to take place, and since the probability of the two reacting molecules being in a Speciftc place is proportional to the product of their Concentrations, the rate of reaction will be proportional to the concentrations of the reactants.. , ... 

In Sec. 2 we saw that the vertical arrows in Fig. 1 denote the process of plunging ions from a vacuum into a solvent. Initially the ionic field exists in the vacuum, and we may say that, in this process, solvent molecules are introduced into this field. In fact, starting with the ion in a vacuum, the final state could equally well be reached by placing molecules in contact with the ion, and continuing to add more and more molecules until the ion is situated in a drop of liquid. In either case each vertical arrow in Fig. 1 denotes a process where solvent molecules are introduced into an intense ionic field and therefore corresponds to the process of introducing a dielectric into the gap between the plates of a condenser which already bears charges +q. 

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