Alkanes

1
Alkanes
C
H
n
2n2
all C are sp3 hybridized
? bonds
n
root
suffix
formula
3 prop ane C3H8 4 but ane C4H10 5
pent ane C5H12
6 hex ane C6H14 7 hept ane C7H16 8
oct ane C8H18 9 non ane C9H20 10 dec ane
C10H22
1
meth
ane
C
H
4
2
C2H6
eth
ane
2
Alkanes
compound
b.p.(Co)
m.w.
CH4 16 -164 C2H6 30 -88.6 C3H8 44 -42.1 C4H10
58 -0.5 C5H12 72 36.0
n 1-4 gases
n 5-15 liquids
n gt 15 solids
3
Alkanes
IMF q1q2
n 1-4 gases
____
r
n 5-15 liquids
n gt 15 solids
LDF
q ?
electrons
instantaneous dipole moments
4
Alkanes
IMF q1q2 r
____
b.p.
compound
m.w.
72
36.1
72
27.9
72
9.5
structural isomers
different shape
same formula
r ?
branching
5
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6
Reactions of Alkanes
combustion
__ C3H8
__ CO2
__ O2 ?
__ H2O
4
5
3
exothermic reaction
combustion with insufficient O2
__ C3H8 __ O2 ? __ CO __ H2O
4
3
7/2
improperly vented spaces and cigarettes
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Reactions of Alkanes
Substitution
of halogens
h?
Cl2 ? 2Cl.
step 1
initiation
propagation
step 2
Cl. CH4 ? CH3. HCl
step 3
CH3. Cl2 ? CH3Cl Cl.
propagation
step 4
Cl. Cl. ? Cl2
termination
get a mixture of chlorinated methanes
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Halogenation of Alkanes
CH3Cl
chloro
methyl chloride
methane
CH2Cl2
chloromethane
methylene chloride
di
CHCl3
chloromethane
chloroform
tri
tetra
CCl4
chloromethane
carbon tetrachloride
all liquids at room temperature
methane is gas
e- rich Cl increases LDF
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Nomenclature
1. Pick longest C chain as parent 2. Number C
beginning at end with first branch 3. Identify
branching substituents Assign each a
number 4. Use commas to separate numbers
hyphens to separate numbers from names 5.
Alphabetize substituents
10
Nomenclature
Structural isomers of C5H12
I.
III.
1
2
3
4
1
2
3
4
2
3
4
II.
1
1
2
3
I.
pentane
II.
butane
methyl
2-
III.
propane
methyl
di
2,2-
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Nomenclature
R alkyl group
1o
3o
primary carbon
tertiary carbon
4o
2o
secondary carbon
quaternary carbon
12
Nomenclature
common names to learn
propyl
iso
alphabetized as i
butyl
sec-
alphabetized as b
butyl
alphabetized as i
iso
tert-
butyl
alphabetized as b