Search results
Results From The WOW.Com Content Network
Polar liquids have a tendency to be more viscous than nonpolar liquids. [citation needed] For example, nonpolar hexane is much less viscous than polar water. However, molecule size is a much stronger factor on viscosity than polarity, where compounds with larger molecules are more viscous than compounds with smaller molecules.
The polar sensitivity factor ρ* can be obtained by plotting the ratio of the measured reaction rates (k s) compared to the reference reaction versus the σ* values for the substituents. This plot will give a straight line with a slope equal to ρ*.
Rather, bond types are interconnected and different compounds have varying degrees of different bonding character (for example, covalent bonds with significant ionic character are called polar covalent bonds). Six years later, in 1947, Ketelaar developed van Arkel's idea by adding more compounds and placing bonds on different sides of the triangle.
Molecules with a polar surface area of greater than 140 angstroms squared (Å 2) tend to be poor at permeating cell membranes. [1] For molecules to penetrate the blood–brain barrier (and thus act on receptors in the central nervous system ), a PSA less than 90 Å 2 is usually needed.
For example, if a compound travels 9.9 cm and the solvent front travels 12.7 cm, the R ƒ value = (9.9/12.7) = 0.779 or 0.78. R ƒ value depends on temperature and the solvent used in experiment, so several solvents offer several R ƒ values for the same mixture of compound. A solvent in chromatography is the liquid the paper is placed in, and ...
Its principal utility is that it provides simple predictions of phase equilibrium based on a single parameter that is readily obtained for most materials. These predictions are often useful for nonpolar and slightly polar (dipole moment < 2 debyes [citation needed]) systems without hydrogen bonding. It has found particular use in predicting ...
A carbon–oxygen bond is a polar covalent bond between atoms of carbon and oxygen. [1] [2] [3]: 16–22 Carbon–oxygen bonds are found in many inorganic compounds such as carbon oxides and oxohalides, carbonates and metal carbonyls, [4] and in organic compounds such as alcohols, ethers, and carbonyl compounds.
In organic chemistry, umpolung (German: [ˈʔʊmˌpoːlʊŋ]) or polarity inversion is the chemical modification of a functional group with the aim of the reversal of polarity of that group. [ 1 ] [ 2 ] This modification allows secondary reactions of this functional group that would otherwise not be possible. [ 3 ]