Search results
Results from the WOW.Com Content Network
Hydrogen-bonding-in-water. A hydrogen bond (H-bond), is a specific type of interaction that involves dipole–dipole attraction between a partially positive hydrogen atom and a highly electronegative, partially negative oxygen, nitrogen, sulfur, or fluorine atom (not covalently bound to said hydrogen atom).
In supramolecular chemistry, [1] host–guest chemistry describes complexes that are composed of two or more molecules or ions that are held together in unique structural relationships by forces other than those of full covalent bonds. Host–guest chemistry encompasses the idea of molecular recognition and interactions through non-covalent ...
Supramolecular polymers are a subset of polymers where the monomeric units are connected by reversible and highly directional secondary interactions–that is, non-covalent bonds. These non-covalent interactions include van der Waals interactions, hydrogen bonding, Coulomb or ionic interactions, π-π stacking, metal coordination, halogen ...
The primary bonds are due to chemisorption, and result in comparatively long lasting covalent and non-covalent bonds. Among covalent bonds disulfide bonds are likely most important. Thiolated polymers – designated thiomers – are mucoadhesive polymers that can form disulfide bonds with cysteine-rich subdomains of mucus glycoproteins. [7]
Molecular self-assembly is a key concept in supramolecular chemistry. [6] [7] [8] This is because assembly of molecules in such systems is directed through non-covalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-stacking interactions, and/or electrostatic) as well as electromagnetic interactions.
These hydrogen bonds are constantly breaking, with new bonds being formed with different water molecules; but at any given time in a sample of liquid water, a large portion of the molecules are held together by such bonds. [61] Water also has high adhesion properties because of its polar nature. On clean, smooth glass the water may form a thin ...
As such, the predicted shape and bond angle of sp 3 hybridization is tetrahedral and 109.5°. This is in open agreement with the true bond angle of 104.45°. The difference between the predicted bond angle and the measured bond angle is traditionally explained by the electron repulsion of the two lone pairs occupying two sp 3 hybridized orbitals.
The hydrogen bonds of water are around 23 kJ/mol (compared to a covalent O-H bond at 492 kJ/mol). Of this, it is estimated that 90% is attributable to electrostatics, while the remaining 10% is partially covalent. [95] These bonds are the cause of water's high surface tension [96] and capillary forces.