Page 10 - Geometry

In the three carboncation structures above, the center carbon atom is attached to either one, two, or three other carbon atoms (represented by R). Depending on whether the carboncation is primary, secondary, or tertiary, the compounds behave differently in chemical reactions. The positive and negative charge bearing compounds formed by heterolytic fission brings us to two more important definitions: electrophile and nucleophile. An electrophile is also called an electron lover. Carboncation is an electrophile. Because of the positive charge and the deficiency of electron, they are acceptors of an electron pair. On receiving a pair of electrons, they form a covalent bond with the donor. A nucleophile, on the other hand, is the electron donor. Because of the access negative charge, they prefer to donate their electron pair to form a covalent bond. Different Types of Organic Reactions As we have already seen, there is a wide variety of organic compounds. These compounds undergo different reactions depending on their respective functional groups. These reactions can be broken down into further steps. The most important of these steps have been explained below. 1. Addition In the addition reactions, two reactants (one of them is usually an alkene) react to produce a single product. For example, the reaction of ethene with bromine gas is an addition reaction. 2. Substitution As the name implies, in substitution reactions, an atom or a group of atoms in one of the reactants is replaced by another. For example, in the presence of sunlight, chlorine substitutes the hydrogen atom(s) from alkanes. The reaction is called the free-radical substitution of alkanes. Page 9 of 20 Study Guide for Organic Chemistry