Interpret the structural properties and spatial isometries

Structural isomerism:

physical properties

1.   have different properties such as:

•   Boiling point
•   melting point
•   density
•   solubility:

for instance:

The n-butanol, boiling punt ° 1180

Isobutanol, boiling point 108 ° C

The atoms involved in a single bond can rotate freely without deterioration, but were not at a double bond, as if it happened, the p pi bond that forms the double bond is broken. Therefore, some alkenes may exist in two different forms, provided that each carbon double bond having different substituent groups

space isomerism

studied organic compounds with the same structural formula but different arrangements of atoms in space.

These isomers differ only in the physical properties.

• geometrical isomerism presented with double bond compounds: carbon - carbon

• the eteroisomeros only be faithfully represented by models in space or perspective drawing

• optical isomerism: Physical and chemical properties have igualesm differ only in the property to divert polarized light

• the enantiomers their mirror images are not superimposable one another, ie are chiral molecules

• conformational isomers are structurally stable, meaning their atoms can not be swapped freely around the links that require the breaking and sharing of atom

interpret graphically the different hybridization and structural and spatial isometries

we must first know what is hybridization;

is a mathematical procedure that It involves combining the individual wave functions for atomic orbitals (pure) s and p to obtain wavefunctions for new atomic orbitals hybrids with different shapes and orientations.

HYBRIDIZATION sp3:

Blending a three 2s 2p
Hybridization called sp3

in each of the vertices marked "sp3" is the C atom to form bonds with H to form the methane molecule, with tetrahedral arrangement. Paired electrons occupy the region of the links which, in turn, form byte about C.

HYBRIDIZATION sp2:

It is defined as the combination of an orbital P S and 2 to form three hybrid orbitals, which are arranged on a plane angles of 120 °.

The atoms forming sp2 hybrids can form compounds with double bonds. Form an angle of 120 ° and the molecule is planar. A single bonds are referred to as sigma bonds (σ) and the double bonds are composed of a sigma bond and a pi bond ().

HYBRIDIZATION sp:

It is defined as the combination of an orbital Sy P, to form 2 hybrid orbital, linear orientation. This is the type of hybrid link with a 180 ° angle and that is existing in compounds with triple bonds and alkynes

It is characterized by the presence of two orbital pi (π).

Secondly we must know what is the isomerism

is a property of those chemical compounds with molecular formula as equal relative proportions of the atoms making up the molecule, they have different chemical structures, and therefore different properties

Structural isomerism:

It is a form of isomerism, where molecules with the same molecular formula have a different distribution of bonds between atoms, contrary to what happens in the stereoisomerism.

Space isomerism:

Exhibit stereoisomerism those compounds having identical molecular formulas atoms and have the same distribution, but their arrangement in space is different, that is, they differ in the spatial orientation of their atoms.

Likewise stereoisomers if they are plotted on a plane. It is necessary to represent them in space to visualize the differences. They can be of two types:

• Conformational isomerism:

isomerism in this type of conversion from one form to another is possible because the rotation around the axis of the bond formed by the carbon atoms is more or less free

• configurational isomerism

Not just a simple rotation to convert one form to another and although the spatial arrangement is the same, are not interconvertible isomers. It is divided into: Geometric or cis-trans isomerism and optical isomerism. Configurational isomers are isolable, since a large amount of energy is needed to interconvertirlos

characterize the types of isomers

those chemical compounds with equal molecular formula (chemical formula undeveloped) equal relative proportions of the atoms making up the molecule, have different chemical structures, and therefore different properties. Such compounds are termed isomers.

• Funcional group isomerism Here, the different atom connectivity, can generate different functional groups in the chain.

• Isomerism compensation or compensation Sometimes it is called isomerism compensation or metamerism of those compounds which function a short carbon chain portions of different lengths

• Structural isomers are molecules with the same molecular formula but the atoms are linked in a different order.

• Stereoisomers: are molecules that have the same connections atom by atom, but differ in the spatial orientation thereof.

Likewise, if they are plotted on a plane. It is necessary to represent them in space to visualize the differences. They can be of two types: conformational isomerism and configurational isomerism, as the isomers can be converted into one another by simple rotation or simple links.

• Enantiomers: they are mirror image stereoisomers nonsuperimposable (each is the mirror image of the other, but may not overlap in space)

• Diastereoisomers: the opposite enantiomers: stereoisomers that have a mirror not including image.

• configurational isomerism

Not just a simple rotation to convert one form to another and although the spatial arrangement is the same, are not interconvertible isomers. It is divided into: geometrical isomerism or cis-trans isomerism and optical:

• Geometrical isomerism or cis-trans

No geometrical isomerism linked to the triple or single bonds is presented.
At two possibilities they are called:

1. cis (or Z form), with the two bulkier substituents on the same side, and
2. trans (or E form), with the two bulkier substituents on opposite positions.

• optical isomerism

• Two enantiomers of a generic amino acid

When a compound has at least one asymmetric carbon atom or chiral, that is, a carbon atom with four different substituents, two different varieties called optical stereoisomers, enantiomers, enantiomorphic forms or chiral forms can be formed, although all atoms are in the same position and similarly linked

characterize the types of orbitals

TYPES OF ORBITAL

Atoms are composed of a heavy nucleus surrounded by light electrons. The behavior of electrons is governed by the rules of quantum mechanics. These rules allow electrons occupy specific regions called orbitals. The interactions of atoms are almost exclusively by their outermost electrons, so that the shapes of these orbitals becomes very important. For example, when atoms approach each other, if their outermost orbital overlap, create a strong chemical bond; then, some knowledge of the shape of the orbit is important to understand the atomic interactions

• And orbital quantum numbers

Physicists have found it convenient to use abbreviations to describe the characteristics of electrons in an atom. The abbreviation is in terms of quantum numbers; these numbers can only be integers, no fractions. The principal quantum number, n, it is related to the electron energy; then, is the orbital quantum number, l, and the angular momentum quantum number, m. Other quantum numbers, but not relate directly to the shape of the orbital. Orbital orbits are not, in the sense of being routes around cores; instead, they represent the positions where it is more likely that the electron will be found.

• Orbital lower order

For each value of n, there is an orbital where m are zero. These orbitals are spheres. The higher the, largest value of n will be the sphere; that is, it is more likely that the electron is farthest from the core. The spheres are not equally dense throughout; It is more likely to be nested shells. For historical reasons, this is called orbital s. Because the rules of quantum mechanics, electrons less energy, with n = 1 and m must be zero, so the only orbital that exists for n = 1 is the s orbital. The orbital s also exists for each different value of n.

• P orbitals

When n is greater than one, more possibilities open. The orbital quantum number, l, may have any value up to n-1. When l equals one, the called orbital p orbital. P orbitals are seen as weights. For each l, m ranges from positive to negative in steps of one. Then for n = 2, l = 1, m can equal 1, 0 or -1. This means that there are three versions of the orbital one with the weight up and down, one with the weight from left to right and one with the weight at right angles to each other. P orbitals exist for all principal quantum number greater than one, but have an additional structure as n increases.

• D orbitals

When n = 3, L may be equal to 2, and when l = 2, m may amount to 2, 1, 0, -1 and -2. Orbital l = 2 are called orbitals, and there are five different types corresponding to different values ​​of m. The orbital n = 3, l = 2, m = 0 is also seen as a weight, but with a donut around the middle. The other four d orbitals look like four eggs stacked one end in a square pattern. The various versions have eggs just pointing in different directions.

• F orbitals

Orbital n = 4, L = 3 is called f orbitals are difficult to describe. They have many complex features. For example, the orbital n = 4, l = 3, m = 0, m = 1 and m = -1 also shaped weights, but now there are two donuts between the ends of the barbell. The other values ​​of m are as a group of eight balloons, with all knots tied together in the middle.

Importance of stereochemistry

The stereochemistry is of great importance in the area of ​​polymers. For example, natural rubber consists of repeating units of cis-polyisoprene, almost 100%, while the synthetic rubber consists of trans-polyisoprene units or a mixture thereof. The resilience of both is different and the physical properties of natural rubber remain well above the physical properties of synthetic.

Other important cases include polystyrene and polypropylene, whose physical properties are increased when its tacticity is correct.

In medicine, the most representative of the importance of stereochemistry case is called thalidomide disaster, a synthetic drug in 1957 in Germany, prescribed to pregnant women to treat morning sickness. However, it was shown that the drug could cause deformities in babies, after which he studied in depth the drug and concluded that an isomer was safe while the other was teratogenic, causing severe genetic damage to the embryo growing. The human body produces a racemic mixture of two isomers, even if only one of them is introduced.

STEREOCHEMISTRY

It is a part of the chemistry that builds on the study of the spatial distribution of the atoms that make up molecules and how this affects the properties and reactivity of these molecules. It can also be defined as the study of the isomers: chemical compounds with the same molecular formula but different structural formulas. Of interest is the study of benzene. An important part of the stereochemistry is dedicated to the study of chiral molecules.

The stereochemistry provides knowledge for chemistry in general whether inorganic, organic, biological, physical chemistry or polymer chemistry.

HISTORY

It is considered to Louis Pasteur as the first chemical in observing and describing the stereochemistry, who, working in 1849 with sales of tartaric acid obtained from wine production, observed that crystals they formed and some of them rotated the plane of light polarized in the direction of clockwise and others against; however, both had the same physical and chemical properties. A final study found a difference, the rotation of the polarized light through the crystals was different in each, plus polarized light of other crystals did not rotate.

Today we know that this property to rotate polarized light due to the optical stereoisomerism. In 1874 Jacobus Henricus van't Hoff and Joseph Le Bel explained the optical activity of these compounds based on the tetrahedron-shaped arrangement formed by the carbon bonds. This is because in the separation space for these four links is greater and therefore the lowest energy corresponds to this form.