25.1

=1. The Structures of Organic Molecules= Tetrahedral: ex: methane (CH4) Trigonal planar: ex: fo rmaldehyde (CH2O) Linear : ex: acetonitrile (CH3CN) toc
 * 3main elements: C,H,O
 * Because carbon has four valence electrons ([ He]2s2ap2), it forms four bonds in virtually all its compounds.
 * Three common geometries around carbon:

Ex: propane (C3H8)
 * Hydrogen atoms are always located on the surface of organic molecule. The C-C bonds form the backbone of the molecule

=2. The Stabilities of Organic Substance=
 * Carbon forms strong bonds with H, O,N and halogens. And carbon can also has ability to bond itsel, forming a varirty of molecules with chains or rings of carbon atoms.
 * Strength: triple bonds> double bonds> single bonds
 * Although the reactions of most organic compounds with oxigen are exothermic, great numbers of them are stable at room temperature because the activation energy required for combustion is large.
 * C-C anad C-H bonds are unreactive because lack of polarity but C-O and O-H involve in chemical reaction because their bonds are quite polar
 * Functional group is the center of reactivity in an organic molecule: ex: C-O-H group in ethanol [[image:http://www.charcoalproject.org/wp-content/uploads/2010/12/Ethanol-11.gif width="278" height="151"]]

=3. Solubility and Acid-Base Properties of Organic Substances=

** Solubility **

 * ===== ﻿ They are generally soluble in nonpolar solvents and not soluble in water=====
 * Molecules that are soluble in polar solvents such as water are those that have polar groups on the surface of the molecule. Ex: glucose, ascorbic acid
 * Soaps and detergents have structure of surfactant organic molecules that have a long, nonpolar part that extends into a polar medium, such as water. ex: stearate

** Acid-Base properties **

 * =====The most important acidic substances are the carboxylic acids, which have functional group -COOH=====
 * The most important basic substances are amines which bear the -NH2, -NHR, -NR2 groups, where R is an organic group consisting of some combination of C-C and C-H bonds