Existence in liquid

Because biomolecules normally exist in liquid water, this article will be largely concerned with their ordered structures in aqueous media and therefore with hydration effects. In order to understand better the influence of solute-solvent interactions on molecular order, also solvation in organic liquids will be considered to some extent. 

Excited states of hydrocarbon molecules often undergo nondissociative transformation, although dissociative transformation is not unknown. In the liquid phase, these excited states are either formed directly or, more often, indirectly by electron-ion or ion-ion recombination. In the latter case, the ultimate fate (e.g., light emission) will be delayed, which offers an experimental window for discrimination. A similar situation exists in liquid argon (and probably other liquefied rare gases), where it has been estimated that -20% of the excitons obtained under high-energy irradiation are formed directly and the rest by recombination (Kubota et al., 1976). 

It is amazingly stable. Apparently, S12 exists in liquid sulfur, because it can be found in quenched melts (91), and it is formed in solutions of Sfl in toluene during decomposition under the influence of light (92). The vapor is, however, unstable thus, mass spectroscopic identiflcation proves to be difficult (12). The molecules have 2/m-C2ft symmetry in the crystal, but are close to Sm-Dg. Table II shows that the bond properties lie between those of Sg and Sg ... 

Equation (4.70) is a starting point in the determination of diffusivities in liquid metal alloys, but in most real systems, experimental values are difficult to obtain to confirm theoretical expressions, and pair potentials and molecular interactions that exist in liquid alloys are not sufficiently quantified. Even semiempirical approaches do not fare well when applied to liquid alloy systems. There have been some attempts to correlate diffusivities with thermodynamic quantities such as partial molar enthalpy and free energy of solution, but their application has been limited to only a few systems. 

Lipids in a biological membrane can exist in liquid-ordered or liquid-disordered states in the latter state, thermal motion of acyl chains makes the interior of the bilayer fluid. Fluidity is affected by temperature, fatty acid composition, and sterol content. 

Tphe rate-limiting processes in catalytic reaction over zeolites remain A largely undefined, mainly because of the lack of information on counterdiffusion rates at reaction conditions. Thomas and Barmby (7), Chen et al. (2, 3), and Nace (4) speculate on possible diffusional limitations in catalytic cracking over zeolites, and Katzer (5) has shown that intracrystalline diffusional limitations do not exist in liquid-phase benzene alkylation with propene. Tan and Fuller (6) propose internal mass transfer limitations and rapid fouling in benzene alkylation with cyclohexene over Y zeolite, based on the occurrence of a maximum in the reaction rate at about 100 min in flow reaction studies. Venuto et al (7, 8, 9) report similar rate maxima for vapor- and liquid-phase alkylation of benzene and dehydro-... 

Liquid crystals, liposomes, and artificial membranes. Phospholipids dissolve in water to form true solutions only at very low concentrations ( 10-10 M for distearoyl phosphatidylcholine). At higher concentrations they exist in liquid crystalline phases in which the molecules are partially oriented. Phosphatidylcholines (lecithins) exist almost exclusively in a lamellar (smectic) phase in which the molecules form bilayers. In a warm phosphatidylcholine-water mixture containing at least 30% water by weight the phospholipid forms multilamellar vesicles, one lipid bilayer surrounding another in an "onion skin" structure. When such vesicles are subjected to ultrasonic vibration they break up, forming some very small vesicles of diameter down to 25 nm which are surrounded by a single bilayer. These unilamellar vesicles are often used for study of the properties of bilayers. Vesicles of both types are often called liposomes.75-77... 

Chamberlain and co-workers (17) have noted that no distinct peak occurs in the infrared absorption spectrum of water below 193 cm.-1. The Raman scattering does give rise to a peak near 60 cm."1 while slow neutron scattering give rise to a number of peaks, including a notable one at 56 cm.-1. This discrepancy implies that a significant number of low frequency oscillations may exist in liquid water with little if any infrared activity. 

The fact that the structure of a solid monomer influences its polymerization substantially now seems obvious. It is not as clear whether structural phenomena can effect polymerization if the monomer is a liquid. It has long been known that ordered regions or clusters exist in liquids, and several years ago it was assumed that in some cases these regions in liquid monomers can influence the polymerization. One of the most vivid examples—namely, polymerization in the liquid-crystalline state—was accomplished by Krentzel and co-workers (I, 2, 3). The object of their study was p-methacrylylhydroxybenzoic acid, which forms conventional crystals in the pure state and does not polymerize in the solid state. However, when mixed with alkoxybenzoic acid, it forms liquid crystals of both smectic and nematic forms. Polymerization of p-meth-acryllylhydroxybenzoic acid in various forms of liquid crystals was compared with polymerization of the same substance dissolved in dioxane and dimethylformamide (DMF). 

Crude Oil A mixture of hydrocarbons that exists in liquid form at atmospheric pressure after passing through surface separating facilities. Included are lease condensate and liquid hydrocarbons produced from tar sands, Gilsonite and oil shale. Drip gases are also included, but topped crude oil (residual) and other unfinished oils are excluded. Liquids produced at natural gas processing plants and mixed with crude oil are likewise excluded where identifiable. 

A solvent is a chemical snbstance that dissolves another chemical substance or snbstances to form a solntion of homogeneous mixture. The solvent is the component in the solution that is present in the largest amount and determines the physicochemical form of the snbstance as either solid, liquid, or gas. Solvents are usually but not necessarily always liquids and can also be gases or solids. The chemical substances dissolved in the solvent are called the solute, and a solvent plus a solute form the solution. The organic solvents share a common structure they are hydrophilic, volatile, and of low molecular weight and exist in liquid form at room temperature. Industrial solvents may be grouped as (1) aliphatic-chain compounds, which include n-hexane or (2) aromatic compounds with a six-carbon ring, which include benzene and xylene. 

What is the nature of wb ( weakly bound ) electrons observed on the short time scale and in solids Does such a species exist in liquid water Are the wb electrons in alcohols partially solvated by their alkyl groups Are these solvent vacancy trapped electrons, as suggested for ice-Ih Are these the same species that are observed in low-temperature solids ... 

Adsorption of both organic and inorganic solutes from the aqueous phase has been a very important application of activated carbons. With current increasing emphasis on the more thorough removal of pollutants from potable and waste waters, the use of carbons and the demands placed on their performance are expected to increase. Many buyers of activated carbon will not be able to afford its underutilization or inefficient use. A similar situation, greatly underutilized carbon adsorbents, exists in liquid chromatography applications, and it has been... 

The number of models that describe the structure and properties of liquid water is enormous. They can be subdivided into two groups the uniform continuum models and the cluster or mixture models. The main difference between these two classes of models is their treatment of the H-bond network in liquid water whereas the former assumes that a full network of H-bonds exists in liquid water, in the latter the network is considered broken at melting and that the liquid water is a mixture of various aggregates or clusters. The uniform continuum models stemmed from the classical publications of Bernal and Fowler, Pople, and Bernal.Among the cluster or mixture models, reviewed in refs 2—6 and 12, one should mention the models of Samoilov, Pauling, Frank and Quist, and Nemethy and Scheraga. ... 

Under these conditions, let us assume a cluster ofNs molecules existing in liquid ofNL molecules. If Ms and Ml are the respective chemical potentials for the two phases, then G for the system can be written as... 

That anodic oxidation does not reveal the existence of M associates for alkali metals in liquid ammonia is consistent with the decrease in the strenght of associates in this solvent. The experimentally determined association constant for Na in hexamethylphosphotriamide equals 2.3x10 and the computed value for ammonia comes to 2.5 x 10 mol 1 To decide whether alkali metal anions exist in liquid ammonia, the oxidation of electrons must be studied at high concentrations of electrons in an intensively stirred concentrated background electrolyte solution. 

The interest in ILs has been generated due to their unique properties and potential uses in areas as diverse as synthesis, biocatalysis, electrochemistry, etc. Thus, this class of molecules is increasingly employed in organic chemistry, material sciences and physical chemistry [3,4], ILs are salts - substances composed exclusively of cations and anions. This fact differentiates them from simple ionic solutions, in which ions are dissolved in a molecular medium. They are also different from inorganic molten salts because their melting points are lower than 100°C (most of them exist in liquid form at or near room temperature). 

Terpenes are flammable unsaturated hydrocarbons, existing in liquid form. They are found in essential oils, resins or oleoresins. They are used as intermediate for the synthesis of sesquitrepenes and terpenoids. They are classified as mono, di or triterpenoids. 

Mercury is a unique element. An extremely heavy metal, it is the only metallic element that exists in liquid form at room temperature. This silvery white metal is a good conductor of electricity, but it is a poor conductor of heat, which is unusual for metals. Scientists have shown that mercury has been known to humanity for thousands of years. People in ancient China knew of the metal, and samples of it have been found in Egyptian tombs dating back to 1500 b.c. While its name comes from the planet Mercury, its chemical symbol, Hg, comes from the Latin word hydragyrum, which means liquid silver. Mercury s primary ore is cinnabar, which is also known as vermillion. This ore, found chiefly in Spain and Italy, contains an abundance of mercury sulfide compounds. Mercury is extracted from cinnabar by heating the ore and then condensing the resulting vapor. 

In view of the specific affinities that exist in liquid systems, the only certain way of getting the best carbon for the job at hand would be to study the performance of all available commercial grades. 

Pak and Chang have previously developed a partition function for liquid water applying the modified theory of significant liquid structure proposed by Chang et al. There, it is assumed that Ice-I-like, Ice-III-like, and gas-like molecules exist in liquid water and the molecules like Ice I and Ice III, both of which are oscillating torsionally, are in thermodynamic equilibrium. The equilibrium constant has been taken equal to the ratio of the partition functions of the two species. Various thermodynamic properties and the surface tension of liquid water from the partition function were successfully calculated. 

Although water and ammonia differ in molar mass by only one unit, the boiling point of water is over 100 °C higher than that of ammonia. What forces in liquid wafer fhaf do not exist in liquid ammonia could account for fhis observation ... 

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