Chapter 1 Introduction Adel M. Awadallah Islamic University of Gaza Organic chemistry for medicine and biology students Chem 2311 Chapter 1 Introduction By Prof. Dr. Adel M. Awadallah Islamic University of Gaza

Ionic Compounds They are formed by the transfer of one or more valence electrons from one atom to another Electropositive atoms: give up electrons and form cations. Electronegative atoms: accept electrons and form anions Ionic compounds: are composed of positively charged cations and negatively charged cations

Covalent compounds A covalent bond: is formed when two atoms share one or more electron pairs. A molecule consists of two or more atoms joined by covalent bonds Bond energy: is the energy necessary to break a mole (6.022 x 1023)of covalent bonds. Bond length: is the average distance between two covalently bonded atoms

Valence and bonding in organic compounds

Polarity of Bonds: depends on the electronegativity difference

Examples:

Isomers: different compounds having the same molecular formula

Abbreviated structural formulas

Formal charge = Valence electrons – bonds – electrons Formal Charges: are the charges that each atom carries, and can be calculated as follows Formal charge = Valence electrons – bonds – electrons Example: Resonance: arises whenever we can write two or more structures for a molecule with different arrangements of electrons but identical arrangement of atoms

Arrows:

Classification of organic compounds according to functional groups