ORGANIC CHEMISTRY 1 212 Chapter 1 Introduction - Chemical Bonding 1-8 جامعة طيبة скачать в хорошем качестве

ORGANIC CHEMISTRY 1 212 Chapter 1 Introduction - Chemical Bonding 1-8 جامعة طيبة

ORGANIC CHEMISTRY 1 212 Chapter 1 Introduction - Chemical Bonding Introduction Chapter 1 Organic chemistry touches our daily lives as much as more than any other branch of science. Almost all the reactions in living matter involve organic substances. The major constituents of living matter including proteins, carbohydrates, lipid (fats) nucleic acids (DNA, RNA), cell membranes, enzymes and hormones are organic compounds. Other organic substances with which we have contact almost daily include the gasoline, oil and tyres for our cars, the clothes we wear, the wood and paper of our furniture and books, the medicines we take when ill, plastic containers, perfumes, carpeting etc. It is part of our technological culture. Organic chemistry is considered the study of most compounds of carbon. These compounds are two kinds. Natural organic compounds: such as petroleum and coal Synthetic organic compounds: such as vitamins, antibiotic, dyes, amino acids and many others. The Uniqueness of Carbon: The number of known organic compounds is over a million and thousands of new ones are synthesized each year. Carbon can form chain or ring. Why does carbon form so many compounds? i- The position of carbon is in the middle of the periodic table. ii- It can form strong bonds with other carbon atoms and with other elements, most commonly with hydrogen, oxygen, nitrogen and halogens. iii- Each organic compound has its own characteristic set of physical and chemical properties, which depend upon the structure of the molecule. Electronic structure of the atom An atom composed of positively charged nucleus (containing protons (P) with positive charge and neutrons (n) with neutral charge) surrounded by a cloud of electrons. The electron density is highest at the nucleus and decreases with increasing the distance from the nucleus in any direction. Electronic configuration of the atom The way to arrange electrons in the orbitals from lowest energy to highest energy levels s- Orbital: occupied by 2 electrons p- Orbital: occupied by 6 electrons d- Orbital: occupied by 10 electrons f- Orbital: occupied by 14 electrons  Electron spin can have only two orientations, up  and down Ø. Only two electrons can occupy an orbital, and they must be of opposite spin (Pauli exclusion principle).  If two or more empty orbitals of equal energy are available, electrons will occupy each with spins parallel until all orbitals have one electron then pairing will be occurred (Hund's rule). Valance Shell: the outermost shell of an atom Valance Electrons: the electrons on the outermost shell of the atom metal. Electronic Configuration Valance Shell Valance Electrons 11 Na: 1S 2 2S 2 2P 6 3S 1 9 F: 1S 2 2S 2 2P 5 8 O: 1S 2 2S 2 2P 4 17 Cl: 1S 2 2S 2 2P 6 3S 2 3P 5 3S 2S & 2P 2S & 2P 3S & 3P Octet Rule: Any atom in the periodic table (except H, He) prefers to have 8 electrons in the valance shell to acquire the electronic distribution of the nearest inert gas in the same period to be stable atom. The atom could loss or gain or char electrons during the formation of the chemical bond to get 8 electrons in the valance shell. Types of Chemical Bonds 1- Ionic Bond Bond between metal (losses electrons and converted into cation) and non-metal (gain electrons and converted into anion) through electron transfer from metal into nonTo form the ionic bond the difference in electronegativity between metals and nonmetals ≥ 1.9 (e.g NaCl) 2- Nonpolar Covalent Bond: Sharing of valance electrons between two similar nonmetals (the difference in electronegativity between two non-metals is less than 0.5) For a covalent bond to be formed two atoms must be located so that an orbital of one overlaps an orbital of the other; each orbital must contain a single electron. When this happens, the two atomic orbitals merge to form a single bond orbital, which is occupied by both electrons. The two electrons that occupy a bond orbital must have opposite spins, that is, must be paired. 3. Polar Covalent Bond The bond between two different atoms with difference in electronegativity ( 0.5 more or Equal D E.N. less 1.9) e.g. H 2 S, HF, HCl, H 2 O Electronegativity: is a measure of the ability of an element to attract electrons of the chemical bond toward itself. The electronegativity increases from left to right within a period and increases from bottom to top in a group in the periodic Table.  If the difference of electronegativity between bonded atoms less 0.5 means nonpolar covalent bond [example N 2 (3-3 = zero)]  If the difference of electronegativity between bonded atoms is equal or higher than 0.5 but lower than 1.9 means polar covalent bond [example (C-Cl) 3-2.5 = 0.5]  If the difference of electronegativity between bonded atoms more or equal 1.9 means ionic bond [example (Na-Cl) 3- 0.9 = 2.1] #chemistry #chemistry212 #organic #organicchemistry #universitychemistry #class #exam #quiz #course #السعودية #جامعة_طيبة #Ibrahim_Soltan