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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 ...
A squaramide organocatalyst typically contains the squaramide group and a hydrogen bond donor which is usually a tertiary amine group. The 3,5-bis(trifluoromethyl)phenyl-group is commonly used for the R group. For enantioselective squaramide catalysis, chirality is induced via the tertiary amine group. There are cases where both sides of the ...
Hydrogen bond: A hydrogen bond is a specific type of dipole-dipole interaction between a partially positive hydrogen atom and a partially negative electron donor that contain a pair of electrons such as oxygen, fluorine and nitrogen. The strength of hydrogen bond depends on the chemical nature and geometric arrangement of each group.
Researchers have since conducted increasingly detailed investigations of the triad's exact catalytic mechanism. Of particular contention in the 1990s and 2000s was whether low-barrier hydrogen bonding contributed to catalysis, [18] [19] [20] or whether ordinary hydrogen bonding is sufficient to explain the mechanism.
The neutral metal carbonyl hydrides are often volatile and can be quite acidic. [5] The hydrogen atom is directly bounded to the metal. The metal-hydrogen bond length is for cobalt 114 pm, the metal-carbon bond length is for axial ligands 176 and 182 for the equatorial ligands.
It is noteworthy that proton-conducting DES (e.g. the mixture of imidazolium methanesulfonate and 1H-1,2,4-triazole in a 1:3 mole ratio or the mixture of 1,2,4-triazolium methanesulfonate and 1H-1,2,4-triazole in a 1:3 mole ratio, wherein the Brønsted base may act as the hydrogen bond donor) have also found applications as proton conductors ...
One example is titanium dihydride, which forms when titanium sponge is heated to 400-700 °C under an atmosphere of hydrogen. These reactions typically require high surface area metals. The direct reaction of metals with H 2 is a step in catalytic hydrogenation. For solutions, classic example involves Vaska's complex: [7]
An important example of molecular recognition is the antibiotic vancomycin that selectively binds with the peptides with terminal D-alanyl-D-alanine in bacterial cells through five hydrogen bonds. The vancomycin is lethal to the bacteria since once it has bound to these particular peptides they are unable to be used to construct the bacteria's ...