Search results
Results from the WOW.Com Content Network
Consequently, hydrogen bonds between or within solute molecules dissolved in water are almost always unfavorable relative to hydrogen bonds between water and the donors and acceptors for hydrogen bonds on those solutes. [44] Hydrogen bonds between water molecules have an average lifetime of 10 −11 seconds, or 10 picoseconds. [45]
Since base pairs are mediated through hydrogen bonding interactions based on hydrogen bond donor-acceptor complementarity, this, in turn, provides a convenient bottoms-up approach towards classifying base pair geometries in terms of respective interacting edges of the participating bases.
The thiourea hydrogen bonds to the nitro group and stabilizes the incoming negative charge, while the amine acts a specific base to activate the nucleophile. This is an example of bifunctional catalysis. Hydrogen-bond catalysis is a type of organocatalysis that relies on use of hydrogen bonding interactions to accelerate and control organic ...
Number of atoms from 20 to 70 (includes H-bond donors [e.g. OHs and NHs] and H-bond acceptors [e.g. Ns and Os]) Veber's Rule further questions a 500 molecular weight cutoff. The polar surface area and the number of rotatable bonds has been found to better discriminate between compounds that are orally active and those that are not for a large ...
Thioureas are often found to be stronger hydrogen-bond donors (i.e., more acidic) than ureas [7] because their amino groups are more positively charged. Quantum chemical analyses revealed that this counterintuitive phenomenon, which is not explainable by the relative electronegativities of O and S, results from the effective steric size of the ...
A metal hydride can be a thermodynamically a weak acid and a weak H − donor; it could also be strong in one category but not the other or strong in both. The H − strength of a hydride also known as its hydride donor ability or hydricity corresponds to the hydride's Lewis base strength. Not all hydrides are powerful Lewis bases.
The red spheres labeled H1 and H2/A3 are, respectively, hydrogen bond donating and accepting sites in the receptor, while L1, L2, and L3 denote lipophilic binding sites. Typical pharmacophore features include hydrophobic centroids, aromatic rings, hydrogen bond acceptors or donors, cations, and anions. These pharmacophore points may be located ...
The hydrogen-donor (transfer agent) is typically isopropanol, which converts to acetone upon donation of hydrogen. Transfer hydrogenations can proceed with high enantioselectivities when the starting material is prochiral: RR'C=O + Me 2 CHOH → RR'C*H−OH + Me 2 C=O. where RR'C*H−OH is a chiral product.