Importance of drawing structures
A structure must be given, otherwise the product of the reaction cannot be determined. The location of single, double, and triple bonds must be specified.

Types of Structures
In Lewis structures, all individual bonds are shown. Formal charge is a way of keeping track of the electrons.  Formal charge is equal to [number of valence electrons] B [nonbonding electrons] B 0.5 [bonding electrons]. In condensed structural formulas, atoms are bonded to a central atom are listed after the atom.  In a skeletal structure, carbon atoms are assumed to be where two lines meet or at the end of the line.  Hydrogens are not shown.  In a sawhorse structure, the drawing is looking down the carbon-carbon bond.

Isomers
Constitutional isomers have the same formula, but different points of attachment.  Configurational isomers have the same formula and the same point of attachment, but different orientation in space.  Conformational isomers have the same formula and the same point of attachment, but the rotation about single bonds is different.  In the eclipsed conformation of ethane, the front hydrogens block the back hydrogens. In the staggered conformation, the hydrogens are as far away from each other as possible.  The staggered conformation is the most stable.  For the conformations of butane, the front two carbons remain in place and the back two carbons rotate around the carbon 2 and carbon 3 bond.  In the totally eclipsed conformation, one methyl blocks the other methyl.  In the gauche conformation, the methyls are 60o apart.  In the eclipsed conformation, the methyls are 120o apart.  In the anti conformation, the methyls are 180o apart.  The stability of butane is anti > gauche > eclipsed > totally eclipsed.

Abbreviations
Me is an abbreviation for methyl, a CH₃-.  Et is an abbreviation for ethyl, a CH₃CH₂-.  Pr is an abbreviation for propyl, a CH₃CH₂CH₂-.  Butyl is an abbreviation for butyl, a CH₃CH₂CH₂CH₂-. Ph is an abbreviation for phenyl, a benzene ring.  Ar is an abbreviation for aromatic or aryl, a benzene ring.  Ac is an abbreviation for acetyl, a methyl next to a C=O.  Bz is an abbreviation for benzoyl, a benzene next to a C=O. Bn is an abbreviation for benzyl, a benzene attached to a CH₂.  Pyr is an abbreviation for pyridine, a six-membered ring with alternating double and single bonds and containing nitrogen.

This tutorial provides the comprehensive coverage of the chapter with easy introduction and simple illustration. It features:

• Concept map showing interconnections of new concepts in this tutorial and those previously introduced.
• Definition slides introduce terms as they are needed.
• Visual representation of concepts.
• Use of colors to emphasis points.
• Compare and contrast of structures and isomers.
• Examples worked out step-by-step throughout the tutorial.
• A concise summary is given at the conclusion of the tutorial.

Importance of Drawing Structures

• Structures, not Formulas
• Show Multiple Bonds

Types of Structures

• Lewis Structures
• Condensed Structures
• Skeletal Structures
• Sawhorse Structures

Isomers

• Constitutional Isomers
• Configurational Isomers
• Conformational Isomers

Abbreviations

• Names
• Structures