1. 1 Chapter 10 Introduction to Organic Chemistry: Alkanes 10.2 Alkanes Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2. 2 Structural Formulas Alkanes are written with structural formulas that are expanded to show each bond. condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C HCH 4, methane H

3. 3 Expanded and Condensed Structures

4. 4 Structural Formulas Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms. Expanded Condensed H H H H │ │ │ │ H─C ─C ─C ─C ─ H CH 3 ─CH 2 ─CH 2 ─CH 3 │ │ │ │ H H H H

5. 5 Names of Alkanes The names of alkanes are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. end in –ane. with 1-4 carbons in a chain use prefixes as follows. Name # Carbons Structural Formula Methane1CH 4 Ethane2CH 3 CH 3 Propane3CH 3 CH 2 CH 3 Butane4CH 3 CH 2 CH 2 CH 3

6. 6 Names of Alkanes Alkanes with 5-10 carbon atoms in a chain use Greek prefixes. Name # Carbons Structural Formula Pentane 5 CH 3 CH 2 CH 2 CH 2 CH 3 Hexane 6 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 Heptane 7 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Octane 8 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Nonane 9 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 Decane 10 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3

7. 7 Learning Check A. Write the condensed formula for: H H H H H H C C C C C H H H H H H B. What is its molecular formula? C. What is its name?

8. 8 Solution A.CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 3 B. C 5 H 12 C. pentane

9. 9 Writing Structural Formulas Carbon atoms in a chain maintain tetrahedral shape. are connected in a zig-zag pattern. are drawn as 2-dimensional. Ccan be written in several conformations.

10. 10 Some Structures for Butane

11. 11 Hexane has Six Carbon Atoms Hexane is an alkane with six carbon atoms in a continuous chain. has a “zig-zag” look because each carbon atom is at the center of a tetrahedron. is represented by a ball-and-stick model as shown below.

12. 12 Learning Check Write the condensed structural formula for A. ethane. B. heptane.

13. 13 Solution Write the condensed structural formula for A. ethane CH 3 ─CH 3 B. heptane CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 3

14. 14 Cycloalkanes are cyclic alkanes. have two hydrogen atoms fewer than the open chain. are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

15. 15 Cycloalkanes The structural formulas of cycloalkanes are usually represented by geometric figures, Cyclopropane CH 2 CH 2 CH 2 Cyclobutane CH 2 CH 2 CH 2

16. 16 More Cycloalkanes Cyclopentane CH 2 CH 2 CH 2 CH 2 Cyclohexane CH 2

17. 17 Learning Check Name the following. A. CH 3 ─CH 2 ─CH 2 ─CH 3 B. C. CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 3 D.

18. 18 Solution Name the following: A. CH 3 ─CH 2 ─CH 2 ─CH 3 butane B. cyclopropane C. CH 3 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 2 ─CH 3 octane D. cyclohexane