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The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the azoles. Thiazoles and isothiazoles contain a sulfur and a nitrogen atom in the ring. Dithioles have two sulfur atoms. A large group of 5-membered ring compounds with three or more heteroatoms also exists.
Geometrical constraints in a molecule can cause a severe distortion of idealized tetrahedral geometry. In compounds featuring "inverted" tetrahedral geometry at a carbon atom, all four groups attached to this carbon are on one side of a plane. [6] The carbon atom lies at or near the apex of a square pyramid with the other four groups at the ...
A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using chemical symbols for the chemical elements, and subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H 2 O.
Moreover, the closing of atoms into rings may lock particular functional group–substituted atoms into place, resulting in stereochemistry and chirality being associated with the compound, including some manifestations that are unique to rings (e.g., configurational isomers); [4] As well, depending on ring size, the three-dimensional shapes of ...
In practice, the term is mainly used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular structure.Typical heteroatoms are nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), chlorine (Cl), bromine (Br), and iodine (I), [2] [3] as well as the metals lithium (Li) and magnesium (Mg).
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. Camphor is a more elaborate example.
The dialkylating group is often a 1,3-, 1,4-, etc. dihalide. [9] In some cases the dialkylating group is a dilithio reagent, such as 1,5-dilithiopentane. [10] For generating spirocycles containing a cyclopropane ring, cyclopropanation with cyclic carbenoids has been demonstrated. [11] Spiro compounds are often prepared by diverse rearrangement ...
For example, two hydrogen atoms adjacent to the carbonyl group in cis-2,6-dimethylcyclohexanone are enantiotopic; they are related by an internal plane of symmetry passing through the carbonyl group, but deprotonation on one side of the carbonyl group or on the other will generate compounds that are enantiomers.