STEREOCHEMISTRY

Stereochemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. An important branch of stereochemistry is the study of chiral molecules. Stereochemistry is also known as 3D chemistry because the prefix "stereo-" means "three-dimensionality".

The study of stereochemistry focuses on stereoisomers and spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question

Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer. The stereochemistry is highly relevant to unnatural systems. Finally, the study of stereochemistry can be used to probe reaction mechanisms. Hence, understanding stereochemistry is necessary for most fields of chemistry, making this chapter one of paramount importance.

CHARACTERIZE THE TYPES OF ORBITAL’S AND ISOMERS

When the group of atoms that make up the molecules of different isomers are bonded together in fundamentally different ways, we refer to such compounds as constitutional isomers.

An orbital is a three dimensional description of the most likely location of an electron around an atom. Alternatively, atomic orbitals refer to functions that depend on the coordinates of one electron (i.e., orbitals) but are used as starting points for approximating wave functions that depend on the simultaneous coordinates of all the electrons in an atom or molecule. The coordinate systems chosen for atomic orbitals are usually spherical coordinates (r, θ, φ) in atoms and cartesians (x, y, z) in polyatomic molecules. The advantage of spherical coordinates (for atoms) is that an orbital wave function is a product of three factors each dependent on a single coordinate. There are typically three mathematical forms for the radial functions R(r) which can be chosen as a starting point for the calculation of the properties of atoms and molecules with many electrons:

·         The hydrogen-like atomic orbitals

·    The slater-type orbital (STO)

       

·         The form of the Gaussian type orbital

Isomers, is a molecule with the same chemical formula as another molecule, but with a different chemical structure. That is, isomers contain the same number of atoms of each element, but have different arrangements of their atoms. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like positional isomers, cis-trans isomers and enantiomers, etc. There are two main forms of isomerism: structural isomerism and stereoisomerism (spatial isomerism).

DIFFERENT HYBRIDIZATIONS AND STRUCTURAL AND SPATIAL ISOMETRIES (GRAPHICALLY)

Orbital hybridization, in simple terms, is a mathematical procedure which involves the combination of the individual wave functions for the atomic orbitals (pure) SYPA obtain wave functions for new hybrid orbitals with different shapes and orientations.

 Following hybridization procedure and possible hybridizations can take the carbon atom based on the mathematical combination of the s and p orbitals are summarized.

Another aspect that is also apparent from this summary table is that carbon atoms form four sp3 single bonds (simple) type sigma. Carbon atoms are sp2 hybridized two single bonds and one double and carbon atoms with sp hybridization form a single bond and one triple.

THE STRUCTURAL PROPERTIES AND SPATIAL ISOMETRIES

The structural theory was the first theory proposed order allowing organic compounds of natural origin that were isolated during the eighteenth and nineteenth centuries. Currently still appear new compounds but initial postulates of structural theory cannot be applied rigorously on these ones. However, the concept of structure in organic compounds has been maintained over the years: The structure of an organic compound is defined by its constitution and stereochemistry. IUPAC also states that the structure of an organic compound is established by its constitution and stereochemistry.