1. Ch. 22 Hydrocarbons

2. Organic Chemistry The study of carbon containing compounds
C bonded to H, N, O, S, P and halogens (17th column)
Hydrocarbon: simplest organic compound that contains only H and C
**because C has four valence electrons, a carbon atoms always forms four covalent bonds

3. Organic vs. Inorganic Organic Inorganic Made of nonmetals (metalloids)
Made of metal & nonmetal
Covalent bonds
Ionic bonds
Most insoluble in water
Most soluble in water
Most soluble in organic solvent
Most non-soluble in organic solvents
Low MP & BP
High MP & BP

4. Alkanes Alkane Hydrocarbon with ALL single bonds
General formula CnH2n+2
Suffix – ane
C Atoms
H Atoms
Formula 3
2(3) + 2 = 8
C3H8 6
2(6) + 2 = 14
C6H14

5. Naming Alkanes A prefix is used to tell the number of C atoms Prefix
Meth – 1
Eth- 2
Prop - 3
But - 4
Pent - 5
Hex - 6
Hept - 7
Oct - 8
Non - 9
Dec - 10

6. Structural Formula Shows the arrangement of atoms
Expanded: all the individual bonds are drawn
Condensed: each carbon is written with the H atoms connected to it
CH3CH2CH3 or CH3 – CH2 – CH3
Line bond: shows the C-C bonds as lines
2 C-C bonds

8. Practice: Draw an expanded formula for butane
Draw the condensed formula for hexane
Draw a line formula for pentane
Name: CH3(CH2)6CH3

9. Practice: Draw an expanded formula for butane
Draw the condensed formula for hexane
Draw a line formula for pentane
Name: CH3(CH2)6CH3
CH3CH2CH2CH2CH2CH3
Octane

10. Branched – Chain Alkanes
A side group called a branch or a substituent is attached to a carbon chain
Also known as a alkyl group
Composed of one or more carbon atoms attached to the carbon chain
Derived from the corresponding alkane by removing one hydrogen
Named by replacing the –ane ending of the corresponding alkane with - yl

11. Naming Branched – Chain Alkanes
The longest chain is named as the main chain
Any carbon branches use their alkyl names
Number the branches by counting the main chain from the end nearest the first side group
Branches are listed in alphabetical order with the number where they are attached (ignore prefixes like di- & tri- when alphabetizing)
If a tie, go with the lowest set of numbers 9 8 7 6 5 4 3
CH3CH2CH2CHCH2CH2CHCH3
6-ethyl-3-methyl nonane 2 1
CH2CH3
CH2CH3

12. Practice: CH3 CH3CH2CH2CCH3 CH3CHCH2CH3 1. 2.
3. Draw 3, 5, 7 - Trimetyldecane

13. Practice: 3, 3, 5 – Trimethyl Heptane 3, 4, 4 – Trimethyl Heptane CH31.
CH3 2.
CH3CH2CH2CCH3
3, 4, 4 – Trimethyl Heptane
CH3CHCH2CH3
3. Draw 3, 5, 7 - Trimetyldecane

14. Propyl vs. Isopropyl
Starting from the bonding point in a normal propyl group there is a continuous string of three carbon atoms.
Starting from the bond point in an isopropyl group the three carbon atoms are not continuous, instead they are branched.

15. Cycloalkanes Ring structures of alkanes Three or more carbon atoms
Two LESS hydrogen atoms in the ring structure
Line Structure:
Shows only the C-C bonds
H atoms on the ring are not shown
Example: cyclohexane

16. Naming Cycloalkanes Name the ring (put cyclo- before alkane name)
Number the ring carbons from the first group
Name the groups with smallest set of numbers
CH3
CH3
CH3
CH3
CH2CH3

17. Naming Cycloalkanes Name the ring (put cyclo- before alkane name)
Number the ring carbons from the first group
Name the groups with smallest set of numbers
CH3
CH3
CH3
CH3
CH2CH3
1, 2 – dimethyl cyclopentane
1-ethyl-1,2-dimethylcyclobutane

18. Properties of Alkanes Nonpolar Low melting and boiling points
Not soluble in water
Low reactivity

19. Saturated vs. Unsaturated Hydrocarbons
Saturated Hydrocarbons: have the maximum number of hydrogen atoms attached to each carbon atom (alkanes)
Unsaturated Hydrocarbons: have fewer hydrogen atoms attached to the carbon chain than alkanes (contain at least one double or triple bond)

20. Alkenes Alkene Contain one or more C = C double bonds
General molecular formula CnH2n
Suffix - ene
Smallest alkene – ethylene

21. Naming Alkenes Use the alkane naming system with a suffix –ene
Double bond MUST be in the longest chain
Number the carbons to get the lowest number on the double bond
If 2 C=C double bonds, use the suffix - diene

23. 1, 3 - pentadiene

24. Properties of Alkenes Similar to alkanes
More reactive due to the double bond

25. Alkynes Contain one or more C  C triple bonds
General molecular formula CnH2n-2
Smallest alkynes …. Common name acetylene
Ethyne: H--CC—H
Properties of Alkynes
Similar to alkanes and alkenes
Even more reactive due to the triple bond
Naming Alkynes
Same as before – suffix -yne

26. Practice:

27. Practice:

28. Isomers
Isomer: structures that have the same molecular formula but different structure
Two types
Structural
Stereoisomers

29. Structural Isomers
Molecules with same chemical formula, but different molecular structures
Structural isomers differ in physical properties such as boiling point and melting point. They also have different chemical reactivities.
Both butane and 2-methylpropane have the molecular formula C4H10.

30. Draw 3 isomers of C5H12

31. Draw the isomers of C4H8

32. Stereoisomers Two types
Stereoisomers: molecules in which the atoms are joined in the same order, but the positions of the atoms in space are different.
Two types
Geometric isomers
Optical isomers

33. Geometric Isomers
Geometric isomers have atoms joined in the same order, but differ in the orientation of groups around a double bond.
Across the double bond, two different conformations can exist
The inflexible double bond does not allow for rotation

34. Cis/Trans Configurations
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.
The groups attached to the carbons of the double bond do not need to be the same.
Geometric isomerism is possible whenever each carbon of the double bond has at least one substituent

35. There is a trans and a cis configuration of 2-butene because a methyl group is attached to each carbon of the double bond.

36. Optical Isomers
Carbon atom has four different atoms or groups attached
A carbon with four different atoms or groups attached is an asymmetric carbon.
Pairs of molecules that differ only in the way that four different groups are arranged around a central carbon atom are called optical isomers.

37. Aromatic Hydrocarbons
Also known as an arene
Contain the benzene ring C6H6
Carbon atoms are joined together by alternating single and double covalent bonds within a cyclic hydrocarbon
Benzene structure is very stable due to the resonance in the ring (that bonds don’t actually alternate and all six bonds are identical)
Ring bonds do not break
H atoms on the ring are replaced w/ R-groups (side groups)

38. 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.

39. Disubstituted benzene
Dimethyl benzenes are also called xylenes
Positions of the disubstitutes can be 1,2; 1,3; or 1,4.
Common names for these benzenes use the terms ortho, meta, and para in place of number

40. Polymers Long-chain molecules consisting of many replacing units
Natural Polymers:
Cellulose in plants
Starches in foods
Proteins & DNA in the body
Synthetic Polymers:
Polyethylene & polystyrene (plastics)
Nylon
Teflon