1. Topic: Alkanes
Do Now: Draw the possible bonds a single carbon atom can have if it has a bonding capacity of 4

2. Alkanes Homologous series of saturated hydrocarbons
Release energy when burned
CnH2n+2 – all have this general formula
CH H
H–C–H H
C2H H H
H–C–C–H
H H

3. Saturated hydrocarbons: organic compounds containing only Single bonds – can’t add any more Hydrogens

4. Properties of Alkanes Low Reactivity
Except readily undergo combustion (fuels)
Nonpolar – don’t dissolve well in water
Low melting & low boiling points
both increase with molecular mass
High vapor pressures

5. Properties of Alkanes Change systematically with # of C’s
As # of C’s increases, boiling point increases
molecules get heavier so harder to change into gas phase

6. Which property is generally characteristic of an organic compound?
Low melting point
High melting point
Soluble in polar solvents
Insoluble in nonpolar solvents
Correct response = A

7. Which of the following compounds has the highest boiling point?
Correct answer = D
nonpolar coval cmpd:
bp depends on strength of van der Waals interactions
van der Waals forces ↑ as size of molecule ↑
bigger molecule = bigger electron cloud

8. Alkanes (CnH2n+2) C3H8 H H H H–C–C–C–H CH3CH2CH3 Chemical Formula
Structural Formula
Condensed Structural Formula

9. straight-chain alkane
H H H H
H–C–C–C–C–H
Or CH3CH2CH2CH3

10. Naming straight-chain Alkanes
Name: describes molecule so can draw it
all alkanes have the suffix –ane
prefix: tells # of C’s

11. C5H12 C4H10 C3H8 C2H6 Meth + ane CH4 Name Formula Ethane Propane
Dec 9
Non 8
Oct 7
Hept 6
Hex 5
Pent 4
But 3
Prop 2
Eth 1
Meth
# of C atoms
Prefix
C5H12
C4H10
C3H8
C2H6
Meth + ane
CH4
Name
Formula
Ethane
Propane
Butane
Pentane

12. Naming Branched-Chain Alkanes
goal of name is to describe molecule so you can draw it

13. Naming branched-chain alkanes
Find longest continuous chain of C atoms
- Bends don’t matter!

14. 2. base name derived from # C’s in continuous chain
9 carbon chain =
nonane

15. triethyl, methyl, propyl
3. Branches named first and in alphabetical order * to name branches, count # C atoms & add “yl” to prefix name * If more than one of same type of branch - use di, tri, etc.
propyl
ethyl
ethyl
methyl
ethyl
triethyl, methyl, propyl

16. Assign number to Branches based on longest carbon chain
Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest #
propyl
ethyl
ethyl 6 3 5 4 7 2 8
methyl 1 9
ethyl
4, 4, 5, 5, 6 = add up = 24

17. Assign number to Branches based on longest carbon chain
Assign number to Branches based on longest carbon chain * you want numbers to add up to the lowest #
propyl
ethyl
ethyl 6 7 4 5 3 8 2
methyl 9 1
ethyl
4, 5, 5, 6, 6 = add up = 26

18. 2. triethyl, methyl, propyl
4. Put it all together
4,4,6-triethyl 5-methyl 5-propyl
nonane
propyl
ethyl
ethyl 6 3 5 4 7 2
1. nonane 8
methyl 1
2. triethyl, methyl, propyl 9
ethyl
3. 4, 4, 5, 5, 6

19. 1 2 3 H 2-methyl propane H–C–H
No because if methyl was anywhere else it wouldn’t be propane H
H–C–H
H H
H–C–C–C–H
H H H 1 2 3
Methyl propane
C4H10
CH3CH(CH3)CH3
Longest continuous chain has 3 carbon atoms – propane

20. Longest continuous chain has 5 C atoms: pentane
Branch: 1 carbon = methyl
Branch: 12 carbon = ethyl
Branch located at C-2 and 3
3-ethly 2-methyl pentane
C8H18
CH3CH(CH3) CH(CH2CH3)CH2CH3 H
H–C–H
H H H
H–C–C–C–C–H
H H H 6 5 4 3 2 1

21. Branched-chain alkanes
Beginning with butane, C4H10, there is more than 1 way to arrange the atoms H
H–C–H
H H
H–C–C–C–H
H H H
ISOMERS