1. Chapter 11 Introduction to Organic Chemistry: Alkanes
General, Organic, and Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 11
Introduction to Organic Chemistry: Alkanes
11.1
Organic Compounds
Lectures
© 2013 Pearson Education, Inc.

2. Organic Compounds An organic compound
typically contains carbon and hydrogen atoms, and
may also contain other atoms, such as, O, S, N, P, or a halogen (F, Cl, Br and I).
Propane, C3H8

3. Properties of Organic Compounds
Many organic compounds
are nonpolar and have weak attractions between molecules.
have low melting and boiling points.
are not soluble in water.
are less dense than water.
are highly flammable.
Oil (organic) and
water (inorganic)

4. Properties of Organic and Inorganic Compounds
Typical properties of organic compounds, such as propane, C3H8, and inorganic compounds, such as sodium chloride, NaCl.

5. Organic Compounds, Bonding
Hydrocarbons
are organic compounds that consist of carbon and hydrogen atoms.
have electron-dot formulas that have four bonds on each carbon atom.
Hydrocarbons with only single bonds are called saturated hydrocarbons.
Methane, CH4 is the simplest hydrocarbon.

6. Tetrahedral Structure of Carbon
VSEPR theory predicts that a carbon atom with four single covalent bonds is tetrahedral as shown in a
A. tetrahedron.
B. ball-and-stick model.
C. space-filling model.
D. expanded structural
formula.

7. Tetrahedral shape of Ethane, C2H6
In ethane,
each carbon atom is bonded to another carbon atom and three hydrogen atoms.
each carbon atom has a tetrahedral shape.
Representations of ethane, C2H6: (a) tetrahedral shape of each carbon, (b) ball-and-stick model, (c) space-filling model, (d) expanded structural formula.

8. Names of Alkanes The names of alkanes
are determined by the IUPAC (International Union of Pure and Applied Chemistry) system.
use a prefix to indicate the number of carbons in a chain.
end in –ane.

9. IUPAC Names for Alkanes
Insert table 11.2 pg 415
The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family.

10. Structural Formulas
Alkanes are written with structural formulas that are
expanded to show each bond.
condensed to show each carbon atom and the attached hydrogen atoms.
In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.

11. Line-Bond Formulas
Because each C atom has a tetrahedral arrangement, the order of atoms is not a straight line, but a zigzag pattern.
A line-bond or skeletal formula abbreviates the carbon atoms and shows only the zigzag pattern of bonds between carbon atoms.
Heptane has 7 carbon atoms.

12. Types of Structural Formulas

13. Rotation Around a C C Single Bond
The groups attached to a C—C single bond
rotate around the bond freely to give different relative structural arrangements called conformations.
sometimes the –CH3 groups line up, sometimes they are opposite each other.

14. Butane, C4H10 Structural Representations
Butane can be drawn using a variety of two-dimensional, condensed structural formulas. Rotation of the end CH3-groups provides different structural arrangements for butane.

15. Drawing Structural Formulas
A molecule of pentane, C5H12 has five carbon atoms connected to each other and to hydrogen atoms with single bonds to give each carbon four bonds.
In a condensed structural formula, carbon atoms
on each end are written as CH3—.
in the middle are written as —CH2—.
The skeletal formula is a zigzag line where the ends and corners represent carbon atoms.

16. Drawing Structural Formulas

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

18. Structures of Cycloalkanes
Cycloalkanes are often represented by skeletal formulas, which appear as a simple geometric figure.

19. Substituents
Alkanes with four or more carbons can have side groups called branches or substituents,
which are attached to the carbon chain.
that replace at least one H on the alkane chain.
When two compounds have the same molecular formula, but differ in the order in which the atoms are bonded, they are called structural isomers.

20. Structural Isomers of C4H10
have the same molecular formula.
have different structural arrangements.
of C4H10 consist of a straight chain and a branched chain, each with 4 carbon atoms.
branch or substituent 20

21. Isomers of Pentane (C5H12)
have the same molecular formula.
have different structural arrangements.
consist of a straight chain and two branched chains. 21

22. Isomers of Alkanes
The number of structural isomers of alkanes increases rapidly as the number of carbon atoms increases.
Insert table of structural
isomers middle pg 420 22

23. Alkyl Groups Alkyl groups are carbon branches.
are named by replacing the -ane ending of the
corresponding alkane name with yl.
methane = methyl
—CH3
ethane = ethyl
—CH2—CH3
propane = propyl
—CH2—CH2—CH3 23

24. Halo Groups Halo groups
are halogen atoms attached to the carbon chain.
are named fluoro (—F), chloro (—Cl), bromo (—Br) or
iodo (—I). 24

25. Common Substituents 25

26. Naming Alkanes with Substituents26

27. Naming Alkanes with Substituents
Name the following alkane. Step 1 Write the alkane name of the longest chain of carbon atoms. 5 C pentane Step 2 Number the carbon atoms starting from the end nearer a substituent. 27

28. Naming Alkanes with Substituents
Name the following alkane. Step 3 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain. 2-methylpentane 28

29. Naming Alkanes with Alkyl Groups
methylpropane
2,4-dimethylpentane 29

30. Naming Haloalkanes In a haloalkane,
halogen atoms replace hydrogen atoms.
substituents are numbered and arranged alphabetically.
alkanes with halogens can be named as alkyl halides; the carbon group is named as an alkyl group followed by the halide name.
CH3—CH2—Cl CH3—Br
IUPAC Name chloroethane bromomethane
Common Name ethyl chloride methyl bromide 30

31. Naming Cycloalkanes with Substituents
When naming a cycloalkane with a substituent
the name of the substituent is placed in front of the cycloalkane name.
the number of the substituent is not needed when there is only one substituent.
If two or more substituent’s are attached, the ring is numbered by assigning carbon 1 to the substituent that comes first alphabetically. 31

32. Naming Cycloalkanes with Substituents
The name of a substituent is placed in front of the
cycloalkane name.
Methylcyclobutane
When there are two substituents, number the ring
1-bromo-2-chlorocyclopentane. 32

33. Guide to Drawing Alkane Structures33

34. What Is in a Name?
The structural formula is drawn from the IUPAC name.
2,4-dimethylhexane
2, dimethyl hexane
Location of Two CH3- groups 6-carbon main chain
branches on attached with single C—C
carbon main chain
atoms 34

35. Alkanes: Physical States
Alkanes are
gases when they have only 1 to 4 carbon atoms.
liquids when they have 5 to 8 carbon atoms.
solids when they have 9 to 17 carbon atoms.

36. Alkanes: Solubility and Density
Alkanes are
nonpolar.
insoluble in water.
less dense than water (1.0 g/mL) with a density from (0.62 g/mL to 0.79 g/mL).
Vegetable oil, an organic compound, is not soluble in water.

37. Alkanes in Oil If there is an oil spill,
alkanes in the oil do not mix with the water,
alkanes form a thin layer on the surface of the water spreading large distances,
cleanup includes mechanical, chemical, and microbiological methods,
In oil spills, large quantities of oil spread over the surface of the water.

38. Alkanes: Melting and Boiling Points
have the lowest melting and boiling points of all organic compounds.
have only nonpolar bonds, C—C and C—H.
have weak dispersion forces which increase when more carbons are present.

39. Branched Alkanes: Melting and Boiling Points
The boiling and melting points of branched alkanes are lower than their straight-chain isomers because they are more compact.
There is more contact between
hexane molecules (red and black
licorice) than between the surfaces
of 2,3-dimethylbutane molecules
(tennis balls).

40. Cycloalkanes: Melting and Boiling Points
Cycloalkanes have
higher boiling points than straight-chain alkanes with the same number of carbon atoms.
restricted rotation around C—C bonds, maintaining rigid structures.

41. Combustion of Alkanes Alkanes
contain single C—C bonds which are difficult to break.
are the least reactive group of organic compounds.
burn readily in the presence of oxygen.
undergo combustion to produce carbon dioxide, water, and energy.

42. Combustion of Alkanes We use methane gas to cook food and heat homes.
Propane gas is used in portable heaters and gas barbecues.
Our cells get energy from the combustion of glucose.

43. Balancing a Combustion Equation
Write the equation:
Balance C:
Balance H:
Balance O with O2:

44. Crude Oil
Hydrocarbons in crude oil are separated by their different boiling points in a process called fractional distillation which removes groups of hydrocarbons by continually heating the mixture to higher temperatures.

45. Crude Oil

46. Elements in Organic Compounds
In organic molecules, carbon atoms can form bonds with atoms of O, S, N, P, or halogens, F, Cl, and Br. 46

47. Functional Groups Functional groups
are a characteristic feature of organic molecules that behave in a predictable way.
are composed of an atom or a group of atoms.
are groups that replace a H in the corresponding alkane.
provide a way to classify families of organic compounds. 47

48. Some Functional Groups48

49. Alkenes and Alkynes
Alkenes contain a double bond between adjacent carbon atoms.
Alkynes contain a triple bond.
Aromatic compounds contain a benzene ring. 49

50. Alcohols, Thiols, and Ethers
An alcohol contains the hydroxyl (–OH) functional group.
Thiols contain a thiol (–SH)
functional group.
In an ether, an oxygen atom is bonded to two carbon atoms (–C–O–C–).
Thiol 50

51. Aldehydes and Ketones
An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom, attached to at least one hydrogen atom.
In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms. 51

52. Carboxylic Acids and Esters
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group.
An ester contains the carboxyl group between carbon atoms. 52

53. Amines and Amides
In an amine, the functional group is a nitrogen atom.
In an amide, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group. 53