Search results
Results from the WOW.Com Content Network
Enantiotopic groups are identical and indistinguishable except in chiral environments. For instance, the CH 2 hydrogens in ethanol (CH 3 CH 2 OH) are normally enantiotopic, but can be made different (diastereotopic) if combined with a chiral center, for instance by conversion to an ester of a chiral carboxylic acid such as lactic acid, or if coordinated to a chiral metal center, or if ...
Modern group names are numbers 1–18, with the 14 f-block columns remaining unnumbered (together making the 32 columns in the periodic table). Also, trivial names (like halogens) are common. In history, several sets of group names have been used, based on Roman numberings I–VIII, and "A" and "B" suffixes. [2] [3
There are 230 space groups in three dimensions, given by a number index, and a full name in Hermann–Mauguin notation, and a short name (international short symbol). The long names are given with spaces for readability. The groups each have a point group of the unit cell.
The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. This is a list of chemical elements by the stability of their isotopes. Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable. [1] Overall, there are 251 known stable isotopes in ...
In the context of nuclear magnetic resonance (NMR), the term magnetic inequivalence refers to the distinction between magnetically active nuclear spins by their NMR signals, owing to a difference in either chemical shift (magnetic inequivalence by the chemical shift criterion) or spin–spin coupling (magnetic inequivalence by the coupling criterion).
The number of protons (Z column) and number of neutrons (N column). energy column The column labeled "energy" denotes the energy equivalent of the mass of a neutron minus the mass per nucleon of this nuclide (so all nuclides get a positive value) in MeV, formally: m n − m nuclide / A, where A = Z + N is the mass number. Note that this means ...
When drawn as a zig-zag chain, the erythro isomer has two identical substituents on different sides of the plane (anti). The names are derived from the diastereomeric four-carbon aldoses erythrose and threose. These prefixes are not recommended for use outside of the realm of saccharides because their definitions can lead to conflicting ...
Structure of Cp′Fe(PPh 3)(CO)I, with labels for the four diastereotopic ring protons. Deprotonation of methylcyclopentadiene gives the aromatic methylcyclopentadienyl anion . [ 2 ] This ion is useful as a ligand for organometallic complexes .