1. Chapt 21 Hydrocarbons [Selected]
21.1 Introduction to Hydrocarbons
21.2 Alkanes [Straight-Chain Only]
21.3 Alkenes & Alkynes (added)
21.4 Hydrocarbon Isomers [also with O]
Mhr , edited, 44 slides not hidden. Added FHS slides to include information on alkenes and alkynes.

2. Section 21.1 Introduction to Hydrocarbons
Hydrocarbons are carbon-containing organic compounds that provide a source of energy and raw materials.
Explain the terms organic compound and organic chemistry.
Identify hydrocarbons
Recognize the different ways that hydrocarbon molecules may be represented (molecular formula, structural formula, ball-and-stick model, etc.) and convert a molecular formula into a valid structural formula and vice versa,
Distinguish between saturated and unsaturated hydrocarbons.

3. Section 21.1 Introduction to Hydrocarbons
Key Concepts
Organic compounds contain the element ??
Hydrocarbons are organic substances composed of carbon and ??.
The major sources of hydrocarbons are petroleum and natural gas.

4. Essential Organic Chemistry
Bond – force that hold atoms together in compounds
Carbon atom (C) always forms 4 bonds with other atoms; bond represented by a line
Hydrogen can only form one bond

5. Simplest Hydrocarbon - Methane
Chemical (molecular) formula: CH4
Structural formula: C H
Chemical bond
Carbon atom with 4 bonds

6. Chapt 21 Hydrocarbons [Selected]
21.1 Introduction to Hydrocarbons
21.2 Alkanes
21.4 Hydrocarbon Isomers [also with O]

7. Section Alkanes
Alkanes are hydrocarbons that contain only single bonds.
Name a straight-chain alkane from its molecular formula or by examining its structure (up to octane).
Draw the structural formula or write the molecular formula of a straight-chain alkane when given its name (up to octane).

8. Alkanes
Simple Alkanes – hydrocarbons with only single bonds and no ring structures
All have formula CnH2n+2 n = integer
All have names ending in “ane”
Simplest = methane
Chemical (molecular) formula: CH4
Structural formula: C H
Chemical bond
Carbon atom with 4 bonds

9. Alkanes n = 2 ethane Chemical (molecular) formula: C2H6
Structural formula:
n = 3 propane
Chemical (molecular) formula: C3H8 C H C H

10. Ethane
Most alkanes rotate freely about the single bond between carbon atoms

11. Two Equivalent Butane Molecules
Right hand structure is twisted version of left hand structure 22

12. Simple Hydrocarbons - Alkanes
Condensed formula helps to see structure
Butane C4 shown as straight-chain isomer
Type of Formula
Molecular Structural Ball-and-Stick Space Fill Condensed
CH3CH3
CH3CH2CH3
CH3CH2CH2CH3

13. Hydrocarbons – Straight-Chain Alkanes
Type of Formula
Name Molecular Condensed

14. Chapt 21 Hydrocarbons [Selected]
21.1 Introduction to Hydrocarbons
21.2 Alkanes [Straight-Chain Only]
21.3 Alkenes & Alkynes
21.4 Hydrocarbon Isomers [also with O]

15. Section 21.3 Alkenes & Alkynes
Alkenes are hydrocarbons that contain at least one double-bond; Alkynes are hydrocarbons that contain at least one triple-bond.
Name a straight-chain alkene or alkyne from its molecular formula or by examining its structure (up to oct-).
Draw the structural formula or write the molecular formula of a straight-chain alkene or alkyne when given its name (up to oct-).

16. Alkenes
Alkenes- hydrocarbons that have one or more double bonds between Carbons
Unsaturated hydrocarbons
Naming: prefix + ene

17. Naming and Drawing Alkenes
Prefix
Name
Structure
Eth-
Ethene
H-CH=CH-H
Prop-
Propene
H-CH=CH-CH2-H
But-
1-Butene
H-CH=CH-CH2-CH2-H
Pent-
1-Pentene
H-CH=CH-CH2-CH2-CH2-H
Hex-
1-Hexene
H-CH=CH-CH2-CH2-CH2-CH2-H
Hept-
1-Heptene
H-CH=CH-CH2-CH2-CH2-CH2-CH2-H
Oct-
1-Octene
H-CH=CH-CH2-CH2-CH2-CH2-CH2-CH2-H

18. Doubles Bonds Can Move, Changes Name of Molecule
Prefix
Name
Structure
But-
1-Butene
H-CH=CH-CH2-CH2-H
2-Butene
H-CH2-CH=CH2-CH2-H
Pent-
1-Pentene
H-CH=CH-CH2-CH2-CH2-H
2-Pentene
H-CH2-CH=CH-CH2-CH2-H
Hex-
1-Hexene
H-CH=CH-CH2-CH2-CH2-CH2-H
2-Hexene
H-CH2-CH=CH2-CH2-CH2-CH2-H
3-Hexene
H-CH2-CH2-CH=CH-CH2-CH2-H

19. Alkynes
Alkynes- are hydrocarbons that have one or more triple bonds between Carbons
Unsaturated hydrocarbons
Naming: prefix + yne
Example: Ethyne (Acetylene) used as a fuel in welding.

20. Naming and Drawing Alkynes
Prefix
Name
Structure
Eth-
Ethyne
H-C=C-H
Prop-
Propyne
H-C=C-CH2-H
But-
1-Butyne
H-C=C-CH2-CH2-H
Pent-
1-Pentyne
H-C=C-CH2-CH2-CH2-H
Hex-
1-Hexyne
H-C=C-CH2-CH2-CH2-CH2-H
Hept-
1-Heptyne
H-C=C-CH2-CH2-CH2-CH2-CH2-H
Oct-
1-Octyne
H-C=C-CH2-CH2-CH2-CH2-CH2-CH2-H
Cn H(2n-2)

21. Chapt 21 Hydrocarbons [Selected]
21.1 Introduction to Hydrocarbons
21.2 Alkanes [Straight-Chain Only]
21.3 Alkenes & Alkynes
21.4 Hydrocarbon Isomers [also with O]

22. Section 21.4 Hydrocarbon Isomers
Some hydrocarbons [and other compounds] have the same molecular formula but have different molecular structures.
Define the terms isomer, structural isomer, and stereoisomer.
Categorize molecular structures as being structural isomers, stereoisomers or as not being isomers.
Distinguish between geometric (diastereomers) and optical isomers (enantiomers)
Differentiate between geometric isomers with cis- and trans prefixes.
Describe describe the structural characteristics that are associated with optical isomers

23. Section 21.4 Hydrocarbon Isomers
Some hydrocarbons [and other compounds] have the same molecular formula but have different molecular structures.
Generate isomers of compounds containing oxygen in addition to carbon and hydrogen

24. Structural (Constitutional)
Types of Isomers
All Isomers
Structural (Constitutional)
Stereoisomers
(Configurational)
Diastereomers
Enantiomers
(optical)
Geometric
(Cis-trans)
Other diastereomers
(>1 chiral centers)

25. Making Butane (C4H10) From Propaneor
propane (C3H8)

26. Butane C4H10. =
Not isomers – carbons connected in same way and forms can convert from one to the other by rotating around a bond =
Structural isomers – carbons connected in different way; bond must be broken to convert one form into the other

27. Structural Isomers of C4H10
Butane, BP = 0°C
Isobutane, BP = -12°C 47

28. Structural Isomers of C5H12 (Pentane)
n-pentane
isopentane
neopentane
Longest continuous carbon chain:
pentane 5 isopentane 4 neopentane 3

29. # of Alkane (CnH2n+2) Structural Isomers
Molecular Formula
Possible # Isomers
C4H10 2
C11H24
159
C5H12 3
C12H32
355
C6H14 5
C15H32
4,347
C7H16 9
C20H42
366,319
C8H18 18
C30H62
4,111,846,763
C9H20 35
C40H82
62,481,801,147,341
C10H22 75

30. Structural (Constitutional)
Types of Isomers
All Isomers
Structural (Constitutional)
Stereoisomers
(Configurational)
Diastereomers
Enantiomers
(optical)
Geometric
(Cis-trans)
Other diastereomers
(>1 chiral centers)

31. Enantiomers - Optical Isomers
Tied to concept of non superimposable mirror images
Familiar example – hands: left & right hands are mirror images but do not superimpose

32. Non-Superimposable Mirror Images
Only when C attached to 4 different groups
When this occurs, C variously referred to as a chiral center, asymmetric carbon, stereogenic center, or stereocenter 67

33. Identifying Chiral Centers
Examine each tetrahedral carbon atom and look at four groups (not the four atoms) bonded to it
If groups all different, have a chiral (stereogenic) center

34. Chiral Molecules - Entantiomers
A pair of nonsuperimposable mirror images are called a pair of enantiomers – these molecules will be optical isomers of each other 69

35. Non-Superimposable Mirror Images
Chiral molecule – mirror images are enantiomers (optical isomers) 72

36. Structural Isomers of C7H16 (Heptane)* *
Isomers marked with * have asymmetric carbons (have enantiomers – optical isomers)

37. Optical Isomers of 3-methylhexane
Tro, Chemistry: A Molecular Approach 77 77

38. Impact of Chirality
Many natural molecules are chiral and most natural reactions are affected by optical isomerism; e.g. D- & L-amino acids!
Many drugs are optically active, with only one enantiomer being beneficial (or harmful, e.g. thalidomide

39. Structural (Constitutional)
Types of Isomers
All Isomers
Structural (Constitutional)
Stereoisomers
(Configurational)
Diastereomers
Enantiomers
(optical)
Geometric
(Cis-trans)
Other diastereomers
(>1 chiral centers)

40. Structural (Constitutional)
Types of Isomers
All Isomers
Structural (Constitutional)
Stereoisomers
(Configurational)
Diastereomers
Enantiomers
(optical)
Geometric
(Cis-trans)
Other diastereomers
(>1 chiral centers)

41. Stereoisomers – No Chiral Centers
Groups on same or opposite sides of double bond – diastereomers (spatially different but not mirror images)

42. Isomers with CHO Compounds
With carbon, hydrogen and oxygen (CHO) present, isomers become more varied
Rule: O in these compounds forms 2 bonds
O found in form of alcohol (COH), ether (COC), or carbonyl (C=O) group

43. Isomers of C3H8O 2 structural isomers in form of alcohol
1 structural isomer in form of ether
ethyl methyl ether
propan-1-ol
propan-2-ol

44. Summary – Isomers
Structural Isomers