1. Chemistry/Physical Setting
Hydrocarbon Compounds
Br. Jabreal

2. Aim: What conventions do chemists use to describe hydrocarbons?
Do Now: What is meant by the term “organic”?

3. Organic Chemistry and Hydrocarbons
Organic chemistry focuses primarily on compounds containing carbon
*Organic compounds are compounds containing carbon
By definition, compounds contain at least two different elements, so organic compounds must contain other elements bonded to the carbon
hydrocarbons: Simplest organic compounds, containing only hydrogen and carbon.

4. Organic Chemistry and Hydrocarbons
Because carbon has four valence electrons, it always forms _______ bonds, in order to complete its octet and become stable like a noble gas.
It can form those four bonds in a variety of ways: in straight chains with four single bonds, combinations of single, double, or triple bonds, or even many times in a ring form

5. Examples of Hydrocarbons
Ex. CH4 (Methane)
Ex. C2H6 (Ethane)
Ex. C2H4(Ethene)

6. Examples of Hydrocarbons
Cyclohexane
Benzene

7. Alkanes Alkane: hydrocarbon with only single covalent bonds.
These are referred to as “saturated” hydrocarbons because they have only single bonds and contain the maximum number of hydrogen atoms a hydrocarbon can have.
Follow general formula of CnH2n+2
n refers to number of carbon atoms in the compound.
For example, if there is 1 carbon, there must be 2(1) + 2 = 4 hydrogens. Thus formula is CH4
Table Q of Reference Tables

8. Practice
An alkane has four carbon atoms. Write the molecular formula for this alkane.

9. Structural Formula of Alkanes
To draw the structural formula of an alkane:
First draw in the straight chain of carbons, each connected to another carbon with a single bond.
Then draw in the remaining bonds for each carbon, ensuring each carbon has four total bonds. The drawn in bonds should connect hydrogen atoms to the carbon.
Ex. C4H10

10. Practice Draw the structural formula for C3H8.
Draw the structural formula for an alkane with five carbon atoms.

11. Condensed Structural Formula
Condensed Structural Formula: Simplified version of the structural formula without the dashed lines.
Bonded carbons are simply written next to each other.
Ex.
Condensed Structural Formula: CH3CH2CH2CH3
Structural Formula

12. Alkenes and Alkynes Alkene: Hydrocarbon with at least one double bond.
Follow general formula of CnH2n
Ex. C2H4
Alkyne: Hydrocarbon with at least one triple bond.
Follow general formula of CnH2n-2
Ex. C2H2

13. Alkenes and Alkynes
*Alkenes and alkynes are considered unsaturated because they have double or triple carbon-carbon bonds.
This makes the ratio of carbon to hydrogen less in these compounds.

14. Practice
How many pairs of electrons are shared between two adjacent carbon atoms in a saturated hydrocarbon?

15. Practice
Explain, in terms of chemical bonds, why the hydrocarbon is unsaturated.

16. Naming Alkanes, Alkenes, and Alkynes
Alkanes, alkenes, and alkynes follow a two-part naming system
The prefix of the name indicates how many carbon atoms are in the parental carbon chain.
Refer to Table P for organic prefixes.
Meth-: one, Eth-: two, Prop-: three, But-: four,
Pent-: five, etc.
The ending of the name indicates if its an alkane, alkene, or alkyne.
Alkane: ends with –ane
Alkene: ends with –ene
Alkyne: ends with -yne

17. Naming Alkanes Example: CH4
There is only one carbon, so we must begin the name with the prefix “meth.”
The formula follows the formula CnH2n+2, so it must be an alkane. The name must end in –ane.
Therefore, the name is methane.

18. Naming Alkanes Example: Propane Prop: contains three carbon atoms
ane: It’s an alkane. It must have all single bonds and follow CnH2n+2. Therefore, it has three carbons and 2(3) + 2 = 8 hydrogens. Thus, the formula of propane is C3H8.

19. Naming Alkenes Example: C4H8
It has four carbons, so it must use the prefix ______.
Since it follows the general formula CnH2n, it must be an alkene. Therefore, the name must end with “ene”.
Name: butene

20. Note: Naming Alkenes
Note: the double bond in an alkene can be in different places.
We state the location of the double bond with a #- before the name.
Ex.

21. Review
Which formula represents an alykne?
CnHn
C2nHn
CnH2n+2
CnH2n-2

22. Review Polyvinyl chloride (PVC) is a polymer used to make
drain pipes, flooring, electric wire, and some plastic
bottles. Making PVC requires several reactions. The first
step is represented by the equation below.
Explain, in terms of chemical bonds, why the
hydrocarbon in equation 1 is unsaturated.

23. Review
What is the difference between 1-butene and 2-butene?

24. Naming Alkynes
Example:

25. Practice
Write the chemical formula, then draw the structural formula, of ethane.
Write the chemical formula of pentane.

26. Practice
Find the molecular formula, and then draw the structural formula for each of the following:
2-Pentene
1-butyne

27. Practice
Name each of the following:
C6H14
C2H4
C7H16
C5H8

28. Naming Alkanes: Branched-chain alkanes
Sometimes alkanes are not just straight chains; they may have carbons branching out from the chain. In these cases, extra detail must be provided in the name.
Ex.

29. Naming Alkanes: Branched-chain alkanes
In cases where there are carbons branching from the alkane chain, two things must be identified:
1. The parental alkane chain
This is identified as the longest carbon chain, although it is not necessarily in a straight line.
2. The substituent groups
These are the groups or carbon chains branching off from the identified parental chain.
If the carbon chain attached has only one carbon, it’s called “methyl.” If there are two carbons in the chain attached its called “ethyl.” For three “propyl.”

30. Naming Alkanes: Branched-chain alkanes
We name the compound by stating the name of the parental chain, and adding the information about the substituent groups before the parental name, in accordance to where the substituent groups are attached.
4-ethyl-2,3-dimethylheptane

31. Practice
Name the following compound:

32. Practice
Draw the structural formula of ethyl-3-methylpentane.

33. Practice
Draw the structural formula of
4-methyl-2-pentene

34. Isomers
Isomers are compounds that have the same molecular formula, but different molecular structures.
Although they may have identical chemical formulas, the arrangement of their atoms are different, giving them different chemical properties.

35. Isomers: Example

36. Practice (June 2017) Which compound is an isomer of C2H5OC2H5?
(1) CH3COOH
(2) C2H5COOCH3
(3) C3H7COCH3
(4) C4H9OH

37. Practice
Draw two isomers of pentene.