Specific intermolecular force

I was thinking particularly of electrostatic interactions between enzyme residues and substrate molecules. Let us compare the hydrophilic cytoplasmic phase (say, with dielectric constant e = 80) and the hydrophobic regions within membranes (say, with e = 2). Is it possible that protein-substrate interactions may be enhanced in certain membrane-associated enzyme schemes That is, might specific intermolecular forces play a more significant role in influencing the site-to-site migration of intermediate substrates, as compared to the same system in the hydrophilic phase [R. Coleman, Biochim. Biophys. Acta, 300, 1 (1973) P. A. Srere and K. Mosbach, Anti. Rev. Microbiol., 28, 61 (1974) and H. Frohlich, Proc. Nat. Acad. Sci. (U.S.), 72, 4211 (1975).]... 

It is customary to divide adsorption into two broad classes, namely, physical adsorption and chemisorption. Physical adsorption equilibrium is very rapid in attainment and is reversible, the adsorbate being removable without change by lowering the pressure. It is supposed that this type of adsorption occurs as a result of the same type of relatively non-specific intermolecular forces that are responsible for condensation of a vapour to liquid. Heat of physical adsorption should be in the range of heats of condensation. It is important for gases below their critical temperature. 

The non-ionic structure a) represents a state without any donor-acceptor interactions, in which only non-specific intermolecular forces hold D and A together. The mesomeric structure b) characterizes a state in which an ionic bond has been formed by... 

We propose the study of Lennard-Jones (LJ) mixtures that simulate the carbon dioxide-naphthalene system. The LJ fluid is used only as a model, as real CO2 and CioHg are far from LJ particles. The rationale is that supercritical solubility enhancement is common to all fluids exhibiting critical behavior, irrespective of their specific intermolecular forces. Study of simpler models will bring out the salient features without the complications of details. The accurate HMSA integral equation (Ifl) is employed to calculate the pair correlation functions at various conditions characteristic of supercritical solutions. In closely related work reported elsewhere (Pfund, D. M. Lee, L. L. Cochran, H. D. Int. J. Thermophvs. in press and Fluid Phase Equilib. in preparation) we have explored methods of determining chemical potentials in solutions from molecular distribution functions. 

Chemical transformations can be performed in a gas, liquid, or solid phase, but, with good reasons, the majority of such reactions is carried out in the liquid phase in solution. At the macroscopic level, a liquid is the ideal medium to transport heat to and from exo- and endothermic reactions. From the molecular-microscopic point of view, solvents break the crystal lattice of solid reactants, dissolve gaseous or liquid reactants, and they may exert a considerable influence over reaction rates and the positions of chemical equilibria. Because of nonspecific and specific intermolecular forces acting between the ions or molecules of dissolved reactants, activated complexes as well as produets and solvent molecules (leading to differential solvation of all solutes), the rates, equilibria, and the selectivity of chemical reactions can be strongly influenced by the solvent. Other than the fact that the liquid medium should dissolve the reactants and should be easily separated from the reaction products afterwards, the solvent can have a decisive influence on the outcome (i.e., yield and product distribution) of the chemical reaction under study. Therefore, whenever a chemist wishes to perform a certain chemical reaction, she/he has to take into account not only suitable reaction partners and their concentrations, the proper reaction vessel, the appropriate reaction temperature, and, if necessary, the selection of flic right reaction catalyst but also, if the planned reaction is to be successful, flic selection of an appropriate solvent or solvent mixture. 

The Interaction Between Glucagon and its Binding Site - The interaction between a hormone and its receptor must ultimately be described in terms of specific intermolecular forces between the two structures. This ideal has not been achieved in the case of polypeptide hormones for many reasons, not the least of which is the complexity of peptide hormone molecules. Fortunately, several fragments of glucagon have recently become available, and these have provided important clues regarding intermolecular forces. 

This specificity through complementariness of structure of the two interacting molecules would be more or less complete, depending on the greater or smaller surface area of the two molecules involved in the interaction. It may be emphasized that this explanation of specificity as due to a complementariness in structure which permits non-specific intermolecular forces to come into fuller operation than would be possible for non-complementary structmes is the only explanation which the present knowledge of molecular structure and intermolecular forces provides. 

Quadrupole relaxation studies of the mobility of covalent compounds have almost exclusively dealt with the pure compounds and medium effects on halogen quadrupole relaxation are virtually unknown. Furthermore, we have seen in the above description of models of molecular motion in liquids and the interpretation of correlation times that the effect of specific intermolecular forces has in most cases been disregarded. For the understanding of the influence of different types of intermolecular interactions on molecular reorientation, systematic studies of quadrupole relaxation in liquid mixtures should be helpful. Halogen relaxation investigations of this type are nonexistent in the literature but a preliminary investigation in our... 

Hence, from a more practical point of view, it seems more advantageous to include in the term solvent polarity the overall solvation ability of a solvent for reactants, activated conq)lexes, and products, as well as for molecules in the electronic ground and excited states. This in turn depends on the action of all possible, specific and non-specific intermolecular forces between solute and solvent molecules(1). 

The interactions between bitter molecules in coffee and molecular receptors on the tongue are highly specific. However, less specific intermolecular forces exisf between all molecules and atoms. These intermolecular forces are responsible for the very existence of liquids and solids. The state of a sample of matter— solid, liquid, or gas—depends on the magnitude of intermolecular forces relative to the amoimt of thermal energy in the sample. Recall from Section 3.10 that the molecules and atoms that compose matter are in constant random motion that increases witir increasing temperature. The energy associated with this motion is... 

Specific intermolecular forces which give rise to the surface tensions do not affect the contact angles directly intermolecular forces determine the surface tensions the surface tensions then determine the contact angle through the Young equation. ... 

K. Ueberreiter, Kautschuk, 19, 12 (1943) Chem. Abstr., 38,4470 (1944). This paper gives the first explicit description of the specific intermolecular forces that give a fixed structure to polymer molecules above T, as discussed in the text. Chem. Abstr. devotes five lines to this paper and misses what we consider to be the important concept presented for the first time. This paper was based on a lecture to the Berlin Chapter of the German Rubber Society on October 13,1942. An exhortation to support the war effort at the front appears at the bottom of the published paper. 

Generally speaking, intermolecular forces act over a short range. Were this not the case, the specific energy of a portion of matter would depend on its size quantities such as molar enthalpies of formation would be extensive variables On the other hand, the cumulative effects of these forces between macroscopic bodies extend over a rather long range and the discussion of such situations constitutes the chief subject of this chapter. 

The equations we have written until now in this section impose no restrictions on the species they describe or on the origin of the interaction energy. Volume and entropy effects associated with reaction (8.A) will be less if x is not too large. Aside from this consideration, any of the intermolecular forces listed above could be responsible for the specific value of x- The relationships for ASj in the last section are based on a specific model and are subject to whatever limitations that imposes. There is nothing in the formalism for AH that we have developed until now that is obviously inapplicable to certain specific systems. In the next section we shall introduce another approximation... 

The attention of this article is focused on physical adsorption, which involves relatively weak intermolecular forces, because most commercial appHcations of adsorption rely on this phenomenon alone. Chemisorption is discussed only briefly in some sections on specific appHcations. 

Where no specific interaction such as hydrogen-bonding can occur between the polymer and the solvent, the intermolecular attraction between the dissimilar molecules is intermediate between the intermolecular forces of the similar species, i.e. 

The van der Waals equation adds two correction terms to the ideal gas equation. Each correction term includes a constant that has a specific value for every gas. The first correction term, a fV, adjusts for attractive intermolecular forces. The van der Waals constant a measures the strength of intermolecular forces for the gas the stronger the forces, the larger the value of a. The second correction term, n b, adjusts for molecular sizes. The van der Waals constant b measures the size of molecules of the gas the larger the molecules, the larger the value of b. 

A gas condenses to a liquid if it is cooled sufficiently. Condensation occurs when the average kinetic energy of motion of molecules falls below the value needed for the molecules to move about independently. Thus, the molecules in a liquid are confined to a specific volume by intermolecular forces of attraction. Although they cannot readily escape, liquid molecules remain free to move about within the liquid phase, hi this behavior, liquid molecules behave like the molecules of a gas. The large-scale consequences of the molecular-level properties are apparent. Like gases, liquids are fluid, so they flow easily from place to place. Unlike gases, however, liquids are compact, so they cannot expand or contract significantly. 

In a liquid, intermolecular forces are strong enough to confine the molecules to a specific volume, but they are not strong enough to keep molecules from moving from place to place within the liquid. The relative freedom of motion of liquid molecules leads to three liquid properties arising from intermolecular forces surface tension, capillary action, and viscosity. ... 

Network solids such as diamond, graphite, or silica cannot dissolve without breaking covalent chemical bonds. Because intermolecular forces of attraction are always much weaker than covalent bonds, solvent-solute interactions are never strong enough to offset the energy cost of breaking bonds. Covalent solids are insoluble in all solvents. Although they may react with specific liquids or vapors, covalent solids will not dissolve in solvents. 

The difference between the log P of a given compound in its neutral form (log P ) and its fully ionized form (log P ) has been termed dialog P ) and contains series-specific information, and expresses the influence of ionization on the intermolecular forces and intramolecular interactions of a solute [44, 51, 52]. 

Solvent selectivity is a measure of the relative capacity of a solvent to enter into specific solute-solvent interactions, characterized as dispersion, induction, orientation and coaplexation interactions, unfortunately, fundamental aiq>roaches have not advanced to the point where an exact model can be put forward to describe the principal intermolecular forces between complex molecules. Chromatograidters, therefore, have come to rely on empirical models to estimate the solvent selectivity of stationary phases. The Rohrschneider/McReynolds system of phase constants [6,15,318,327,328,380,397,401-403], solubility... 

Hybrid MPC-MD schemes may be constructed where the mesoscopic dynamics of the bath is coupled to the molecular dynamics of solute species without introducing explicit solute-bath intermolecular forces. In such a hybrid scheme, between multiparticle collision events at times x, solute particles propagate by Newton s equations of motion in the absence of solvent forces. In order to couple solute and bath particles, the solute particles are included in the multiparticle collision step [40]. The above equations describe the dynamics provided the interaction potential is replaced by Vj(rJVs) and interactions between solute and bath particles are neglected. This type of hybrid MD-MPC dynamics also satisfies the conservation laws and preserves phase space volumes. Since bath particles can penetrate solute particles, specific structural solute-bath effects cannot be treated by this rule. However, simulations may be more efficient since the solute-solvent forces do not have to be computed. 

In van der Waals equation, it is the term n2a/V2 that is of interest in this discussion, because that term gives information about intermolecular forces. Specifically, it is the parameter a that is related to inter-molecular forces rather than the number of moles, n, or the volume, V. It should be expected that the... 

To confirm the above reasoning, use boiling points given below to indicate strengths of intermolecular forces. Remember, the lower the boiling point is, the weaker the intermolecular forces present in the liquid, and the higher the vapor pressure at a specific temperature. 

Supramolecular aggregations are commonly referred to by a variety of terms, including adduct, complex, and van der Waals molecule. In this chapter we shall primarily employ the more neutral term cluster, which may, if desired, be qualified with the type of intermolecular interaction leading to clustering (e.g., H-bonded cluster ). General and specific types of intermolecular forces are discussed in the following sections. 

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