1. Chapter 22 “Hydrocarbon Compounds”
Mr. Gower
Troy High School

2. Organic Chemistry and Hydrocarbons
“Organic” originally referred to any chemicals that came from organisms
German chemist Friedrich Wohler synthesized urea in a lab
Today, organic chemistry is the chemistry of virtually all compounds containing the element carbon

3. Friedrich Wohler
1800 – 1882
Used inorganic substances to synthesize urea, a carbon compound found in urine.
This re-defined organic chemistry.

4. Organic Chemistry and Hydrocarbons
Over a million organic compounds, with a dazzling array of properties
Why so many? Carbon’s unique bonding ability!
Let’s start with the simplest of the organic compounds. These are the Hydrocarbons.

5. Organic Chemistry and Hydrocarbons
Hydrocarbons contain only two elements: 1) hydrogen, and 2) carbon
simplest hydrocarbons called “alkanes”, which contain only carbon to carbon single covalent bonds (CnH2n+2)
methane (CH4) with one carbon is the simplest alkane. It is the major component of natural gas.

6. Organic Chemistry and Hydrocarbons
Review structural formulas - p.694
Carbon has 4 valence electrons, thus forms 4 covalent bonds
not only with other elements, but also forms bonds WITH ITSELF (nonpolar)
Ethane (C2H6) is the simplest alkane with a carbon to carbon bond

7. Organic Chemistry and Hydrocarbons
One carbon atom can form a single covalent bond with four hydrogen atoms.

8. Organic Chemistry and Hydrocarbons
Formulas and Models for Methane and Ethane
Ball-and-stick model
Space-filling model
Different types of formulas and models can be used to represent hydrocarbons such as methane and ethane. Interpreting Diagrams What does a stick in a ball-and-stick model represent?

9. Straight-Chain Alkanes
Straight-chain alkanes contain any number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight)
C-C-C C-C-C-C etc.
Names of alkanes always will always end with -ane

10. Alkanes Straight-Chain Alkanes
Ethane is the simplest of the straight-chain alkanes, which contain any number of carbon atoms, one after the other, in a chain.

11. Straight-Chain Alkanes
Combined with the -ane ending is a prefix for the number of carbons
-Table 22.1, page 695
Homologous series- a group of compounds that have a constant increment of change
In alkanes, it is: -CH2- (methylene)

12. Alkanes
A group of compounds forms a homologous series if there is a constant increment of change in molecular structure from one compound in the series to the next.

13. Alkane MP and BP- Van der Waals Forces.

14. Straight-Chain Alkanes
Many alkanes used for fuels: methane, propane, butane, octane
As the number of carbons increases, so does the boiling and melting pt.
The first 4 are gases; #5-15 are liquids; higher alkanes are solids
Condensed structural formulas? Note examples on page 696

15. Alkanes

16. Naming Straight-Chain Alkanes
Names recommended by IUPAC - the International Union of Pure and Applied Chemistry
end with –ane; the root part of the name indicates the # of carbons
We sometimes still rely on common names, some of which are well-known

17. Naming Straight-Chain Alkanes
IUPAC names may be long and cumbersome
Common names may be easier or more familiar, but usually do not describe the chemical structure!
Methane is natural gas or swamp gas

18. Branched-Chain Alkanes
Branched-chain means that other elements besides hydrogen may be attached to the carbon
halogens, oxygen, nitrogen, sulfur, and even other carbons
any atom that takes the place of a hydrogen on a parent hydrocarbon is called a substituent, or the branched part

19. Alkanes Branched-Chain Alkanes
An atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule is called a substituent.

20. Branched-Chain Alkanes
A hydrocarbon substituent is called an alkyl group or sometimes radicals
use the same prefixes to indicate the number of carbons, but -ane ending is now -yl such as: methyl, ethyl, propyl, etc.
Gives much more variety to the organic compounds

21. Branched-Chain Alkanes
Rules for naming – (go from right to left) - page 698
1. Longest C-C chain is parent
2. Number so branches have lowest #
3. Give position number to branch
4. Prefix (di, tri) more than one branch
5. Alphabetize branches (not prefix)
6. Use proper punctuation ( - and , )

22. - Page 699

23. Branched-Chain Alkanes
From the name, draw the structure, in a right-to-left manner:
1. Find the parent, with the -ane
2. Number carbons on parent
3. Identify substituent groups (give lowest number); attach
4. Add remaining hydrogens

24. - Page 700

25. Alkanes A hydrocarbon substituent is called an alkyl group.
An alkane with one or more alkyl groups is called a branched-chain alkane.

26. Practice- page 699

27. Alkanes Draw 3-ethylpentane Draw 2,3,4-trimethylhexane
Since the electrons are shared equally, the molecule is nonpolar
thus, not attracted to water
oil (a hydrocarbon) not soluble in H2O
“like dissolves like”

28. 22.1 Section Quiz.
1. Choose the correct words for the spaces. Because carbon has ______ valence electrons, it can form ______________ bonds.
a. four, four covalent
b. four, four ionic
c. six, six covalent
d. six, four or fewer covalent

29. 22.1 Section Quiz.
2. Alkanes are hydrocarbons that contain only ___________ bonds.
a. carbon-carbon
b. single covalent
c. carbon-hydrogen
d. ionic

30. 22.1 Section Quiz
3. Choose the correct words for the spaces. Hydrocarbons are highly soluble in _______ solvents because they are ________ molecules.
a. nonpolar, nonpolar
b. nonpolar, polar
c. polar, nonpolar
d. polar, polar

31. Alkenes Multiple bonds can also exist between the carbon atoms
Hydrocarbons containing carbon to carbon double bonds are called alkenes (CnH2n) C=C C-C=C
Called “unsaturated” if they contain double or triple bonds

32. Naming Alkenes Find longest parent that has the double bond in it
New ending: -ene
Number the chain, so that the double bond gets the lower number
Name and number the substituents
Samples on page 702

33. Alkenes
Alkenes are hydrocarbons that contain one or more carbon-carbon double covalent bonds.

34. Alkenes
Because rotation is restricted around the double bond, atoms in ethene lie in one plane.
Ethene
Because rotation is restricted around the double bond, atoms in ethene lie in one plane. Calculating What is the ratio of hydrogen to carbon in ethene?

35. Alkynes
Hydrocarbons containing carbon to carbon triple bonds are called alkynes
(CnH2n-2) C C-
Alkynes are not plentiful in nature
Simplest is ethyne- common name acetylene (fuel for torches)
Table 22.3, p. 703 for boiling pt.
ethyne

36. Alkynes
At least one carbon-carbon bond in an alkyne is a triple covalent bond. Other bonds may be single or double carbon-carbon bonds and single carbon-hydrogen bonds.

37. Alkynes Alkenes and alkynes are unsaturated!
Straight-chain and branched-chain alkanes, alkenes, and alkynes are aliphatic hydrocarbons.

38. Alkenes

39. Alkynes
The triple bond restricts rotation in an ethyne molecule, which has a linear shape.
The triple bond restricts rotation in an ethyne molecule, which has a linear shape. Calculating What is the ratio of hydrogen to carbon in ethyne?

40. 22.2 Section Quiz.
1. Alkenes and alkynes are called unsaturated compounds because they contain
a. single bonds only.
b. double or triple bonds.
c. oxygen atoms.
d. hydrogen atoms.

41. 22.2 Section Quiz.
2. What is the correct name for a compound with a C-C-C=C-C carbon skeleton?
a. 3-pentyne
b. 2-pentene
c. 3-pentene
d. 4-pentene

42. 22.2 Section Quiz. 3. Which of the following substances is an alkyne?
a. C6H12
b. C2H4
c. C2H2
d. C4H8

43. Structural Isomers
Compounds that have the same molecular formula, but different molecular structures, are called structural isomers
Butane and 2-methylpropane (made by breaking carbon off the end, and making it a branch in the middle)
Also have different properties, such as b.p., m.p., and reactivity

44. Structural Isomers of Butane, C4H10

45. Stereoisomers
Don’t forget that these structures are really 3-dimensional
stereoisomers- molecules of the same molecular structure that differ only in the arrangement of the atoms in space. Two types are a) geometric and b) optical

46. Geometric Isomers
There is a lack of rotation around a carbon to carbon multiple bond
has an important structural implication
Two possible arrangements:
1. trans configuration - substituted groups on opposite sides of double bond
2. cis configuration - same side

47. Geometric Isomers
Substituted groups are on opposite sides of the double bond (in this case, one is above, the other is below)
Trans-2-butene
Substituted groups are on the same side of the double bond (in this case, both are above)
Cis-2-butene

48. Geometric Isomers Trans-2-butene and Cis-2-butene shown on page 705
differ in the geometry of the substituted groups (to double bond)
like other structural isomers, have different physical and chemical properties ( note page 705-middle)

49. Geometric Isomers
In the trans configuration, the methyl groups are on opposite sides of the double bond.
In the cis configuration, the methyl groups are on the same side of the double bond.

50. Optical Isomers
Asymmetric carbon? C with 4 different groups attached. Conceptual Problem 22.4, p.706
Molecules containing asymmetric carbons have “handedness”, and exist as stereoisomers.
Figure 22.9, page 705

51. Optical Isomers, and these will each show an asymetric carbon (4 different branches attached)
The asymetric carbon

52. Stereoisomers

54. 22.3 Section Quiz
1. Structural isomers have different properties because they have
a. a different number of bonds.
b. different types of bonds.
c. different substituents.
d. a different order of atoms.

55. 22.3 Section Quiz
2. Substituent groups on opposite sides of a double bond are said to be in the _______ configuration. If the groups are on the same side of the bond, then they are in the _______ configuration.
a. cis, trans
b. trans, cis
c. trans, iso
d. stereo, cis

56. 22.3 Section Quiz
3. Geometric isomers have different arrangements of atoms
a. and different molecular formulas.
b. but only single bonds.
c. around an asymetric carbon.
d. around a double bond.

57. 22.3 Section Quiz
4. A carbon atom that has four different substituents always forms
a. an optical isomer.
b. a saturated hydrocarbon.
c. a geometric isomer.
d. an unsaturated hydrocarbon.

58. Cyclic Hydrocarbons
The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon
sample drawings on page 709
named as “cyclo- ____”
hydrocarbon compounds that do NOT contain rings are known as aliphatic compounds

59. Cyclic Hydrocarbons Three Ways to Represent Cyclic Hydrocarbons
The simplest cyclic hydrocarbon has a 3-carbon ring. Rings containing up to 20 carbon atoms are found in nature. Rings with 5 or 6 carbons are the most abundant.

60. Aromatic Hydrocarbons
A special group of unsaturated cyclic hydrocarbons is known as arenes
contain single rings, or groups of rings
also called “aromatic hydrocarbons”, because of pleasant odor
simplest aromatic is benzene (C6H6)
Term “aromatic” applies to materials with bonding like that of benzene

61. Aromatic Hydrocarbons
Benzene is a six-carbon ring, with alternating double and single bonds
exhibits resonance, due to location of the double and single bonds-p.710
Benzene derivatives possible:
methylbenzene, 3-phenylhexane, ethylbenzene (top page 711)

62. Aromatic Hydrocarbons
The Structure of Benzene
Benzene can be shown as switching, or resonating, between two arrangements of alternating double and single bonds.

63. Aromatic Hydrocarbons
The three symbols below can be used to represent the benzene ring. If the bonds are shown as alternating single and double bonds (on right), it is important to remember that bonds don’t actually alternate and that all six bonds are identical.

64. Aromatic Hydrocarbons
Space-filling Model of Benzene
This is a space-filling model of benzene. Applying Concepts What is the molecular formula of benzene?

65. Aromatic Hydrocarbons
Substituted Aromatic Compounds
Compounds with a substituent on a benzene ring are named as a derivative of benzene. When benzene is a substituent, it is called a phenyl group.

66. Aromatic Hydrocarbons
A benzene ring can have two or more substituents.

67. Aromatic Hydrocarbons
The molecules of many dyes include benzene rings.
The molecules of many dyes include benzene rings. Dyes that contain aromatic compounds are called aniline dyes.

68. Aromatic Hydrocarbons
One derivative of Benzene is called phenylethene, or commonly named STYRENE.
Foamed styrene is trademarked by Dow Chemical as “styrofoam”
Other manufacturers items usually just called “foam cups”
CH2 CH

69. Aromatic Hydrocarbons
Benzene derivatives can have two or more substitutents:
1,2-dimethylbenzene
1,3-dimethylbenzene
1,4-dimethylbenzene
Can use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711) C C C C

70. 22.4 Section Quiz.
1. Choose the correct words for the spaces. Alkanes that do not contain a ring structure are _______ hydrocarbons. Alkanes that do contain ring structures are called _________ hydrocarbons.
a. aliphatic, aromatic
b. aromatic, aliphatic
c. aliphatic, cyclic
d. aromatic, cyclic

71. 22.4 Section Quiz.
2. The carbon-carbon bonds in a benzene molecule are
a. alternating double and single bonds.
b. identical hybrid bonds.
c. all double bonds.
d. all single bonds.

72. 22.4 Section Quiz.
3. When an alkane has a benzene ring as a substituent, the ring is called _______ group.
a. a benzene
b. a toluene
c. a phenyl
d. an arene

73. Natural Gas Fossil fuels provide much of the world’s energy
Natural gas and petroleum contain mostly the aliphatic (or straight-chain) hydrocarbons – formed from marine life buried in sediment of the oceans
Natural gas is an important source of alkanes of low molecular mass

74. Natural Gas Natural gas is typically:
80% methane, 10% ethane, 4% propane, and 2% butane with the remainder being nitrogen and higher molar mass hydrocarbons
also contains a small amount of He, and is one of it’s major sources

75. Natural Gas
Natural gas is prized for combustion, because with adequate oxygen, it burns with a hot, clean blue flame:
CH4 + 2O CO2 + 2H2O + heat
Incomplete burning has a yellow flame, due to glowing carbon parts, as well as making carbon monoxide

76. Petroleum
The compounds found in petroleum (or crude oil) are more complex than those in natural gas
Usually straight-chain and branched-chain alkanes, with some aromatic compounds also
Crude oil must be refined (separated) before being used

77. Petroleum
It is separated by distillation into fractions, according to boiling pt.
Fractions containing higher molar mass can be “cracked” into more useful shorter chain components, such as gasoline and kerosene
involves catalyst and heat
starts materials for plastics and paints

78. Natural Gas Wells are drilled to reach natural gas and petroleum. 22.5
Wells are drilled to reach natural gas and petroleum. Pressure from the trapped gas may force petroleum up a well pipe, but pumping is usually required.

79. 22.5
Petroleum
In fractional distillation, the crude oil is heated so that it vaporizes and rises through the fractionating column. The column is hotter at the bottom and cooler at the top.
In fractional distillation, the crude oil is heated so that it vaporizes and rises through the fractionating column. The column is hotter at the bottom and cooler at the top. Compounds with the highest boiling points condense near the bottom. Compounds with the lowest boiling points condense near the top.

80. 22.5
Petroleum

81. Coal
From huge fern trees and mosses decaying millions of years ago under great pressure of rocks / soil.
Stages in coal formation:
1. Peat- soft, fibrous material much like decayed garden refuse; high water content. After drying will make a low-cost, smoky fuel

82. Coal
2. Lignite- peat left in the ground longer, loses it’s fibrous texture, and is also called brown coal
harder than peat; higher C content (50%); still has high water content
3. Bituminous, or soft coal- formed after more time; lower water content, higher C content (70-80%)

83. Coal 4. Anthracite, or hard coal
carbon content exceeding 80%, making it an excellent fuel source
Coal may be found close to the surface (strip-mined), or deep within the earth
Pollutants from coal are common; soot and sulfur problems

84. 22.5
Coal
Coal Formation
Coal formed when tree ferns and mosses died and were subjected to continued pressure and heat underground.
Coal formed when tree ferns and mosses died. The layers of decaying organic material were compressed over millions of years between layers of soil and rock. The first stage in coal formation is peat. Continued pressure and heat transform peat into lignite, bituminous coal, and anthracite coal.

85. 22.5
Coal
Coal consists largely of condensed aromatic compounds of extremely high molar mass. These compounds have a high proportion of carbon compared with hydrogen.

86. Coal Coal is mined from both surface mines and underground mines. 22.5
Coal is mined from both surface mines, shown here, and underground mines.

87. Note the size of the man standing next to it.
BIG BRUTUS
Dragline used to remove the overburden of a strip mining coal field near West Mineral, Kansas.
Note the size of the man standing next to it.

88. Coal Coal may be distilled for many products
coal gas, coal tar, coke, and ammonia
further distilled into benzene, toluene, naphthalene, phenol- the aromatics
Coke is almost pure carbon; produces intense heat and little or no smoke, thus used in industrial processes

89. End of Chapter 22