Solutions of Long Chain Compounds

The solubility of a polymer in a non-polymeric liquid depends mainly on the heat of mixing. When no polar forces are concerned, the cohesive energy densities of polymer and solvent must be close; a method is given for estimating the cohesive energy densities of polymers from a set of additive constants, and it is shown that good agreement is found between values so calculated and values obtained by swelling measurements. The effects of dipole interactions and hydrogen bonding are also discussed. The solubility of polyvinyl chloride in a number of solvents is considered, and correlated with both the cohesive energy density of the solvent and its ability to form hydrogen bonds.

Some factors affecting the solubility of polymers

Among many various kinds of molecular interactions, the H-bond has a special position. The term is ubiquitous in the world that surrounds us, but also it is often applied in different ways. The H-bond is of great importance in natural sciences. This relates particularly to biological aspects, such as molecular recognition that could be a basis for the creation of life,1-4 formation of higher order structures of peptides and nucleic acids,5 and biochemical processes, particularly the enzymes catalyzed.6,7 One can say that the H-bond plays a double role in biological systems: on one hand, as a relatively strong directional interaction, it leads to relatively stable supramolecular structures, and on the other hand, because of dynamic features of the proton, it is an active site for initiation of chemical reactions. H-bonds are the source of specific properties of associated liquids, with water being the most popular among them.8 Water as a medium in which life was most probably created is saturated by H-bonds with highly mobile protons in between, even in the solid state.9 In many crystal lattices of organic compounds, the H-bonds are a decisive factor governing packing.10 In designing new interesting crystal structures, which is the subject of fast developing crystal engineer* To whom correspondence should be addressed. E-mail: slagra@ uni.lodz.pl or slagra@ccmsi.us. Fax: +48-42-6790447. 3513 Chem. Rev. 2005, 105, 3513−3560

Interrelation between H-bond and Pi-electron delocalization.

A relation of the form k=aN(xAxB/d2)34+b has been found to hold accurately for a large number of diatomic and simple polyatomic molecules in their ground states. (The average deviation of k calculated from k observed for seventy‐one cases is 1.84 percent.) Here k is the bond‐stretching force constant, d the bond length, N the bond order, and xA and xB are the electronegativities of the bonded atoms. If k is measured in dynes/cm×10−5 and d in Angstrom units, a and b have the values 1.67 and 0.30, respectively, for stable molecules exhibiting their normal covalencies, except those in which both bonded atoms have only one electron in the valence shell; for diatomic molecules of the alkali metals, Na2, NaK, etc., a and b are 1.180 and −0.013, respectively; for hydrides of elements having a single electron in the valence shell, 1.180 and 0.040, respectively; and for diatomic hydrides of elements having two to four electrons in the valence shell, 1.42 and 0.08, respectively. Numerous applications of the relatio...

A Relation between Bond Force Constants, Bond Orders, Bond Lengths, and the Electronegativities of the Bonded Atoms

Quantitative measures of solvent polarity.

The strengths of deuterium bridges formed between heavy water and forty‐two different basic solvents are compared by measurements of the perturbations which the solvents produce on the OD vibrational band of heavy water which occurs at 3.59 μ in heavy water vapor and at 4.00 μ in liquid heavy water. The solvents were selected from the following classes: ketones, ethers, esters, glycols, nitriles, amides, ketoximes and amines. The proton‐attracting properties of twenty‐five solvents are compared by measurement of the strengths of the hydrogen bonds which they form by sharing the proton of hydrogen chloride. Heavy water was found more satisfactory for strong and moderately weak bases; hydrogen chloride, for extremely weak bases. The shifts which the different liquids produce upon the D2O band and the HCl band are compared with the shifts which the same solvents produce on the OD vibrational band of CH3OD. A linear relation was found in each case, with frequent but small variations from linearity. Basicity constants were known from other measurements for nineteen of the solvents used with D2O. The shifts which these solvents produce on the D2O band were found to be directly proportional to the logarithms of their basicity constants. The method used here promises to be practical for comparing basicities of numerous types of compounds. The close relation existing between the hydrogen bond theory and modern theories of acids and bases is discussed.

Spencer C. Stanford

Papers

Erratum: Spectroscopic Evidence for Hydrogen Bonds: Comparison of Proton‐Attracting Properties of Liquids. IV

Spectroscopic Evidence for Hydrogen Bonds: SH, NH and NH2 Compounds

Thermodynamic Properties of the Hexyl Alcohols. II. Hexanols-1, -2, -3 and 2-Methylpentanol-1 and -4

Spectroscopic Evidence for Intermolecular Hydrogen Bonds between Phenylacetylene and Various Organic Solvents

Spectroscopic Evidence for Hydrogen Bonds: The Hexyl Alcohols. I