Bond Chemical Delokal dan Resonance

Delokal bonding found in compounds containing unsaturated one or more bonding orbitals are not limited to the two atoms, but spread up to three atoms or more. Such a bond is called bond delokal. In the valence bond method, to describe the actual structure of Such molecules, several Lewis structures (canonical form) is written, then taken their average weight. The weight of an average of two or more forms called resonance.

Bond Energy

There are two types of binding energy. The energy required to break a bond produce the radical is called dissociation energy D. For example D for H2O → HO + H is 118 kcal / mol. However, this value is not selected as the binding energy OH in water because of D for HO → H + O is 100 kcal / mol. The average of these two values The (109 kcal / mol) was chosen as the binding energy E. For methane, the total energy change of CH4 into C + 4H (at 0 K) is 393 kcal / mol. This means E for the CH bond in methane is 98 kcal / mol at 0 K. In the molecular diatoms, of course D = E. The heat of combustion is known exactly is burning hothydrocarbons. For methane, combustion heat value at 25oC was 212.8 kcal / mol, which leads to heat atomisasinya value is 398.0 kcal / mol (At 25oC), or the value of E for CH bond is 99.5 kcal / mole at 25oC.  

Bond angle

Sp3 carbon bond angle can be expected is always equal to the tetrahedral 109o28 ', but this can only happen if the four clusters are bound are identical as in methane, neopentana, or carbon tetrachloride. Most cases are found where there has been little deviation from the angles in pure tetrahedarl. As examples of CC-Br angles in 2-bromopropana is 114.2 o. A similar found deviations from the point of 120o to 180o angle to sp2 and sp. This deviation occurs because of slight differences hybridization.

Long bond

The distance between the atoms in the molecule is characteristic of molecules and can provide valuable information when compared with the same bond in different molecules.

The primary method of determining the bond length and angle is the x-ray diffraction (for solids), electron diffraction (only for gas), and methods spektroskofi.

Induction and Field Effects

CC bond in ethane is perfect because the bond is nonpolar connecting the two atoms are equivalent. However, the C-C bond in kloroetana polarized by the presence of electronegative chlorine atoms. This polarization is actually the sum of two effects.

Covalent Molecules Ionic Character

It is known that in the bond A - B where A and B have differences in electronegativity, the bond is purely covalent. As an example we using hydrochloric acid. 

Electronegativity

Electronegativity is a concept that is raised by chemists as the development of the phenomenon of a permanent dipole moment caused by asymmetric molecules. Electronegativity is defined as the latent power of an atom within a molecule to attract electrons. This concept depends on theoretical structure of modern organic chemistry to interpret some properties such as: strength of acidity and alkalinity, chemical bond lengths, ionic character, volatility, solubility, redox potential, hydrogen bond strength, and others.

Lewis Structure

The structure of molecules, ions, or free radicals which have only electron possible localized written with a formula that shows the location of electrons, and called Lewis structures. This formula shows only valence electrons, both found in the covalent bond that links two atom, or as free electrons. The structure of a molecule must be written with true because the position of the electron can change in a reaction, and it is important to know the initial position of the electron prior to drill down to where berpindahannya. For can write the formula of a molecular electronics properly it is necessary to apply

rules as follows:

A STUDY OF ELECTRONIC STRUCTURE OF AZOBENZENE MOLECULE AND ITS DERIVATIVES

Azobenzene-based conjugate of organic molecules have been known to have a large second order nonlinear optical properties. With this property, the molecules have a promise of potential to be developed into variety photonics devices, Such as optical switching, optical memory, as well as grating. A variation of the nonlinear properties of the molecules cans be controlled by choosing a Suitable of Donor-Acceptor That group attached on both sides of azo dyes. Hence, the study of the molecular structure is Important. Through this study, the Correlation Between its molecular structure and physical properties of cans be found. One of the Important methods to analyze the information about molecular structure is UV / Vis spectroscopy.

Multiple bond

If the ethylene molecules are reviewed according to the concept of molecular orbitals, carbon in the molecule using sp2 orbital to form bonds with three other atoms. Orbital hybridisation sp2 emerged from 2s1, 2px1, and 2py1. Each of the three carbon atoms of ethylene binding through σ bonds, one to each hydrogen atom, and one to the other carbon. Each carbon atom has one electron in the 2pz orbital, and based on the principle of maximum repulsion then the orbital is perpendicular to the plane of sp2 orbitals. Two parallel 2pz orbitals overlap laterally to produce two new hybrid orbitals, the π bonding orbital and orbital anti-bonding π *. Orbital σ ellipsoid-shaped and symmetrical around the axis CC.orbitals Π in the form of two ellipsoid, one above and one below. Own field declared node.