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In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH 3) "turns inside out". [1] [2] It is a rapid oscillation of the atom and substituents, the molecule or ion passing through a planar transition state. [3]
In bridged bicyclic compounds, the two rings share three or more atoms, separating the two bridgehead atoms by a bridge containing at least one atom. For example, norbornane , also known as bicyclo[2.2.1]heptane, can be viewed as a pair of cyclopentane rings each sharing three of their five carbon atoms.
In the context of chemistry, cis indicates that the functional groups (substituents) are on the same side of some plane, while trans conveys that they are on opposing (transverse) sides. Cis – trans isomers are stereoisomers , that is, pairs of molecules which have the same formula but whose functional groups are in different orientations in ...
The main method of systematic nomenclature is to follow with square brackets containing the number of atoms in the smaller ring then the number of atoms in the larger ring, separated by a period, in each case excluding the spiroatom (the atom by which the two rings are bonded) itself.
Protein secondary structure is the local spatial conformation of the polypeptide backbone excluding the side chains. [1] The two most common secondary structural elements are alpha helices and beta sheets , though beta turns and omega loops occur as well.
The methylene bridge (methanediyl group) In organic chemistry, a methylene bridge, methylene spacer, or methanediyl group is any part of a molecule with formula −CH 2 −; namely, a carbon atom bound to two hydrogen atoms and connected by single bonds to two other distinct atoms in the rest of the molecule.
The main chain–main chain hydrogen bond is replaced by a side chain–main chain hydrogen bond. 3D computer superimposition shows that, in proteins, they occur [12] as one of the same four types that beta turns do, except that their relative frequency of occurrence differs: type II’ is the most common, followed by types I, II and I’.
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition.