Case Western Reserve University Organic Chemistry 4th Edition Paula Yurkanis Bruice Chapter 2 An Introduction to Organic Compounds Nomenclature, Physical Properties, and Representation of Structure Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall

Alkanes are hydrogen carbons containing only single bonds General formula: CnH2n+2

Constitutional isomers have the same molecular formula, but their atoms are linked differently

Nomenclature of Alkyl Substituents

A C7H16 compound can be any one of the following: A compound can have more than one name, but a name must specify only one compound A C7H16 compound can be any one of the following:

Different Kinds of Carbons and Hydrogens

Nomenclature of Alkanes 1. Determine the number of carbons in the parent hydrocarbon 2. Number the chain so that the substituent gets the lowest possible number

3. Number the substituents to yield the lowest possible number in the number of the compound (substituents are listed in alphabetical order) 4. Assign the lowest possible numbers to all of the substituents

5. When both directions lead to the same lowest number for one of the substituents, the direction is chosen that gives the lowest possible number to one of the remaining substituents 6. If the same number is obtained in both directions, the first group receives the lowest number

7. In the case of two hydrocarbon chains with the same number of carbons, choose the one with the most substituents 8. Certain common nomenclatures are used in the IUPAC system

Nomenclature of Cycloalkanes 1. No number is needed for a single substituent on a ring 2. Name the two substituents in alphabetical order

3. If there are more than two substituents,

Nomenclature of Alkyl Halides In the IUPAC system, alkyl halides are named as substituted alkanes

Different Kinds of Alkyl Halides

Nomenclature of Ethers As substituents:

Nomenclature of Alcohols In an alcohol, the OH is a functional group A functional group is the center of reactivity in a molecule 1. Determine the parent hydrocarbon containing the functional group

2. The functional group suffix should get the lowest number 3. When there is both a functional group suffix and a substituent, the functional group suffix gets the lowest number

4. If there is more than one substituent, the substituents are cited in alphabetical order

Nomenclature of Amines The substituents are listed in alphabetical order and a number or an “N” is assigned to each one

Naming Quaternary Ammonium Salts

Structures of Alkyl Halides

Structures of Alcohol and Ether

Structures of Amines

Dipole–dipole interaction Attractive Forces van der Waals force Dipole–dipole interaction Hydrogen bonds The greater the attractive forces between molecules, the higher is the boiling point of the compound

van der Waals Forces The boiling point of a compound increases with the increase in van der Waals force

Dipole–Dipole Interaction Dipole–dipole interactions are stronger than van der Waals force but weaker than ionic or covalent bonds

A hydrogen bond is a special kind of dipole–dipole interaction

Like Dissolves Like Polar compound dissolves in polar solvent Nonpolar compound dissolves in nonpolar solvent

Conformations of Alkanes: Rotation about Carbon–Carbon Bonds

Different Conformations of Ethane A staggered conformer is more stable than an eclipsed conformer Torsional strain: repulsion between pairs of bonding electrons

Conformations of n-Butane Steric strain: repulsion between the electron clouds of atoms or groups

Cycloalkanes: Ring Strain Angle strain results when bond angles deviate from the ideal 109.5° bond angle

The chair conformation of cyclohexane is free of strain

Ring Flipping in Cyclohexane

Drawing Cyclohexane

The Conformations of Cyclohexane and Their Energies

Conformations of Monosubstituted Cyclohexanes

Steric Strain of 1,3-Diaxial Interaction in Methylcyclohexane

The larger the substituent on a cyclohexane ring, the more the equatorial substituted conformer will be favored Keq = [equatorial conformer]/[axial conformer]

The Chair Conformers of cis-1,4-Dimethylcyclohexane

The Chair Conformers of trans-1,4-Dimethylcyclohexane

1-tert-Butyl-3-Methylcyclohexane

Conformations of Fused Rings Trans-fused cyclohexane ring is more stable than cis-fused cyclohexane ring