1. Ch. 10: Alkanes
Chem 20
El Camino College

2. Organic Chemistry More than 90% of compounds are organic compounds.
For pronunciation of organic compound names go to

3. Organic Chemistry
Organic chemistry covers compounds made of carbon and hydrogen
Other elements, such as O, N, S and Cl may be present

4. Organic Chemistry Organic compounds
They are mostly covalently bonded molecules
Usually low melting points
Usually low boiling points
They are usually not soluble in water, unless a polar group is present

5. Organic Chemistry Inorganic compounds
They are mostly ionic compounds, some are covalent
Usually high melting points
Usually high boiling points
They are usually soluble in water.

6. ALKANES Remember that carbon has 4 bonds and is often tetrahedral.
Wedge formula: Solid wedge represents bond coming forward. Broken wedge represents bond going to the back.
Ordinary line represents bond on the plane

7. Lewis Structures
Each bonding pair is represented by a dash. Sometimes we draw long molecules with straight lines, but actually they are not flat

8. Alkanes
Alkanes are a class of hydrocarbons in which the atoms are connected only by single bonds.
The general formula for open-chain alkanes is Cn H2n+2 .

9. Alkanes CH4 methane (1C) CH3CH3 ethane (2C) CH3CH2CH3 propane (3C)
CH3CH2CH2CH3 butane (4C)
CH3CH2CH2CH2CH3 pentane (5C)
CH3CH2CH2CH2CH2CH3 hexane (6C)
CH3CH2CH2CH2CH2CH2CH3 heptane (7C)
CH3CH2CH2CH2CH2CH2CH2CH3 octane (8C)
CH3CH2CH2CH2CH2CH2CH2CH2CH3 nonane (9C)
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 decane (10C)

10. Drawing Formulas In expanded formulas, every bond is shown
In condensed formulas, carbons are shown with the correct number of hydrogen atoms, but not every bond is shown
In alkane, C will always have 4 bonds, H will always have 1 bond

11. Drawing Formulas

12. Drawing Formulas
Hexane has six carbons. Draw expanded and condensed formulas for hexane. (Note: make sure every carbon has 4 bonds)

13. Drawing Formulas
Note--the chains in formulas may not be shown as a straight line.
Ex. What compounds are these?
butane heptane

14. Skeletal (Geometric)Formula (Stick structure)
Skeletal formulas contain zigzag lines
Every corner and every end represents a carbon
H atoms are filled in mentally
Butane:
Hexane

15. Structural Isomers
Isomers have the same chemical formula, but atoms are attached differently
2 different isomers have different properties
Are these isomers, or the same molecule?
isomers
same molecule

16. Stereoisomers
In stereoismers atoms are attached to each other in the same way
But they are different in the way atoms are oriented in space
Chiral center is a carbon atom to which 4 different groups are attached.

17. Fisher projection A cross represents a chiral center.
Vertical lines represent bonds going away to the back
Horizontal lines represent bond coming forward

18. Cycloalkanes Cycloalkanes have the carbons connected in a “ring”
Use cyclo in the name
Ex. Condensed formula for cyclohexane
Draw a geometric formula for cyclopropane.
What is the chemical formula?
C3H6

19. Substituents Alkanes can have attachments Common attachment names:
CH3- methyl
CH3CH2- ethyl
CH3CH2CH2- propyl
F-, Cl-, Br-, I- fluoro, chloro, bromo, iodo
isopropyl

20. Alkanes with Substituents
1. Write the name of the longest continuous carbon chain
The longest chain has 5 carbons: pentane

21. Alkanes with Substituents
2. Number the carbon chain from the end nearer a substituent
3. Give the location and name of the substituent. Use a hyphen after the number
2-methylpentane

22. Alkanes with Substituents
Name these
2-chloropentane
3-chloropentane

23. Alkanes with Substituents
Name these
2-bromopropane
3-methylheptane

24. Alkanes with Substituents
Name these, write the formula
4-ethylnonane
C11H24
1-bromohexane
C6H13Br
3-methylnonane
C10H22

25. Alkanes with Substituents
Draw the skeletal formula
Draw the expanded formula
2-bromobutane
1-chlorodecane
1-iodopropane
cyclobutane

26. Alkanes with Substituents
Name these, write the formula
2-fluorohexane
C6H13F
cyclopentane
C5H10
4-propylheptane
C10H22

27. Alkanes with Substituents
4. Name substituents in alphabetical order
2-bromo-1-iodohexane
Name this
3-bromo-2-methylpentane

28. Alkanes with Substituents
Name these
1-bromo-2-chlorobutane
2-chloro-1-fluorobutane
1-bromo-1-fluoro-2-methylpropane

29. 5. Use prefixes like di-, tri-, tetra- for more than one copy of a substituent
Every substituent must have its own number
Prefixes are not part of alphabetical order.

30. 2,3-dimethylbutane
2,2-dibromobutane
1,2,2-trichlorobutane

31. 6. When there are 2 or more substituents, the main chain is numbered to give the lowest set of numbers
Which is correct:
1,5-dibromo-6-chloro-5-methylhexane or
2,6-dibromo-1-chloro-2-methylhexane?

32. 1,2-dibromo-3-methylbutane
1,2-dibromobutane
3-bromo-2-fluoropentane

33. 7. When a single substituent is attached to a cycloalkane, no number is needed.
chlorocyclohexane
Write the name and chemical formula:
ethylcyclobutane
C6H12

34. Draw these ethane 2-methylpropane bromocyclopentane
1,4-dichloro-2-methylbutane
1,1,2,3-tetrabromopropane

35. Properties, Uses Alkanes are nonpolar, so they’re insoluble in water
Alkanes are less dense than water (they float on water)
Common alkanes: methane (natural gas), propane (bbq fuel), butane (lighter fuel), octane (fuel)
Alkane mixtures also form gasoline, mineral oil, and vaseline.

36. Combustion
The burning of methane in a Bunsen burner is an example of combustion of an alkane
alkane + O2 ® CO2 + H2O + energy
Write a balanced equation for the combustion of methane gas
_____(g) O2(g) ® CO2(g) H2O(g)
CH4 2 2

37. Compound Types Alkenes (contain C=C) Alkynes (contain CºC)
Alcohols (contain -OH)
Ethers (contain C-O-C)
Aldehydes (contain H-C=O)
Ketones (contain C=O)
Carboxylic acids (contain HO-C=O)
Esters (contain RO-C=O)
Amines (contain N).

38. Un-Numbered 10.11a

39. Un-Numbered 10.12a

40. Un-Numbered 10.12b

41. Un-Numbered 10.13a

42. Un-Numbered 10.13b

43. Un-Numbered 10.14

44. Un-Numbered 10.15a

45. Un-Numbered 10.15b

46. Un-Numbered 10.16

47. What is the compoud type?
ester
alkene
carboxylic acid
ketone
aldehyde
amine
alkane

48. Substitution Reactions
Your next organic reactions will be on haloalkanes (alkanes with a halogen atom substituent)
In substitution reactions, one halogen will be substituted for another halogen
CH3Br + Cl- ® CH3Cl + Br-

49. Draw Products, Name the Organic Product
chloroethane

50. Draw Products, Name the Organic Product
2-chloro-2-methylpropane

51. Name These bromoethane bromoethane 1,1-dibromoethane 1,2-dibromoethane
1,1,2-tribromoethane

52. Name These 2-bromopropane 2-bromo-2-methylpropane
1,2-dibromo-2-methylpropane
1,1,1,2-tetrabromo-2-methylpropane

53. Draw Products, Name the Organic Product
bromocyclohexane