Thermodynamic Properties of Hydrogen Bonds

The fascination of a growing science lies in the work of the pioneers at the very borderland of the unknown but to reach this frontier one must pass over well travelled roads of these one of the safest and surest is the broad highway of thermo-dynamics,  

Having defined the H bond and presented the qualitative evidence for its occurrence, we may now consider quantitative behavior. Since a H bond is formed in an equilibrium reaction, the thermodynamic equations are applicable. Fortunately, many cases involve fairly simple equilibria in a temperature range which is readily available (usually between 0 and 200°C). 

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Thermodynamic Properties of Hydrogen Bonds TABLE 7-III -AH Values of the H Bond in Ice... 

Table 4 reports some thermodynamic properties of hydrogen bonded N—H O complexes of aniline and (V-methylaniline. Chloroform (Table 3) as proton donor towards... 

Lewis GN, Randall M (1960) Thermodynamic properties of hydrogen bonds. In Pimentel GC, McClellan AL (eds) The hydrogen bond. Freeman, San Francisco, pp 206-225 Lorenz JC, Teufel LW, Warpinski NR (1991) Regional fractures I a mechanism for the formation of regional fractures at depth in flat-lying reservoirs. Am Assoc Pet Geol Bull 75 1714-1737... 

Because intermolecular hydrogen bonds between small molecules are usually made and broken very rapidly relative to the chemical shift difference between bonded and nonbonded forms (expressed in hertz), separate lines are generally not observed for different species, and the frequency v of the single observed line is given by Eq. 2.58. In suitable systems the variation of v with concentration and temperature can be analyzed to give equilibrium constants and other thermodynamic properties for hydrogen bond formation. 

The present review is, in a sense, a continuation of aU three aforementioned reviews. The thermodynamic aspects of hydrogen bonding (combinatorial approach) in pme fluids and their mixtures will be presented in a way that can be combined with any thermodynamic model. Here, it should become clear at the outset that, in general, hydrogen bonding makes a contribution only and is not sufficient for the complete evaluation of the various thermodynamic properties of fluids and their mixtures. Thus, hydrogen-bonding formalisms are usually combined with thermodynamic models, which account for all other contributions collectively called physical contributions. For the purposes of this chapter, we will use two kinds of thermodynamic frameworks equation-of-state theories (EoS) and predictive (infinite dilution) activity coefficient models. 

Thermodynamic and physical properties of water vapor, Hquid water, and ice I are given ia Tables 3—5. The extremely high heat of vaporization, relatively low heat of fusion, and the unusual values of the other thermodynamic properties, including melting poiat, boiling poiat, and heat capacity, can be explained by the presence of hydrogen bonding (2,7). 

The reason is that classical thermodynamics tells us nothing about the atomic or molecular state of a system. We use thermodynamic results to infer molecular properties, but the evidence is circumstantial. For example, we can infer why a (hydrocarbon + alkanol) mixture shows large positive deviations from ideal solution behavior, in terms of the breaking of hydrogen bonds during mixing, but our description cannot be backed up by thermodynamic equations that involve molecular parameters. 

There are two major experimental techniques that can be used to analyze hydrogen bonding in noncrystalline polymer systems. The first is based on thermodynamic measurements which can be related to molecular properties by using statistical mechanics. The second, and much more powerful, way to elucidate the presence and nature of hydrogen bonds in amorphous polymers is by using spectroscopy (Coleman et al., 1991). From the present repertoire of spectroscopic techniques which includes IR, Raman, electronic absorption, fluorescence, and magnetic resonance spectroscopy, the IR is by far the most sensitive to the presence of hydrogen bonds (Coleman et al., 1991). 

Suresh, S J. and Naik, V.M. 2000. Hydrogen bond thermodynamic properties of water from dielectric constant data. J. Chem. Phys. 113, 9727-9732. 

An alternative approach is possible. Just at the coefficients B, C, D, etc. define the thermodynamic properties of the real fluid so coefficients B°, C°, D°, etc. define thermodynamic properties for a hypothetical fluid which we will call the primary fluid. The primary fluid can be regarded as having the properties which the real fluid might have in the absence of association. It is assumed that when secondary interactions such as hydrogen bonding are imposed on the primary fluid the real fluid will be simulated. This assumption is an acceptable approximation at low densities, but is unlikely to hold at high densities where the addition of hydrogen bonds may produce new structural features. 

Abstract—This paper is an analysis of measurements of the thermodynamic properties of aqueous solutions of non-electrolytes, which has been made in order to establish both the relative strength of different kinds of hydrogen bonds in such solutions and the correlation between bond-strengths and the phase-behaviour of the solutions. The thermodynamic properties are compared with the results of statistical theories of solutions and with the properties of more simple solutions. 

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