Chapter 12:
Intro to Organic Chemistry
Chapter 13:
Alkenes & Alkynes
Organic Chemistry
· The chemistry of carbon compounds
Carbons provide primary framework
Other atoms like H, O, N, halogens attached
H
H
O‒H
H‒C‒C‒C‒H
H
H
H
· Originally thought to be naturally occurring
chemicals
But can now synthesize any number of large,
complex “artificial” compounds
Carbon Framework
Carbons ⇒ have 4 valence electrons
⇒ form 4 bonds to get 8 shared e‒’s
C
+
H
H C H
H
H
H C H
H
x
x
4xH
x
x
x
Can arrange series of C’s with 4 bonds in
infinite number of combinations
CH3 - CH2
CH3
CH3 – CH2 - C - CH2 - CH - CH3
CH3 - CH2
H
C2H8O
OH
CH3 - CH2 – CH2
Condensed formula
• H’s listed after C that
H’s attached to
O‒H
H‒C‒C‒C‒H
H
Chemical formula
H
H
H
Structural formula
OH
Line formula
• Draw C-C bonds
• Assume C at each
“corner” or “end”
• Assume H’s fill rest of
octet rule
Isomers
Different molecules having same chemical formula
CH3
CH3 - CH – CH3
CH3 – CH2 – CH2 – CH3
C4H10
C4H10
2-methylpropane
butane
melting pt = – 160ºC
boiling pt = – 12ºC
melting pt = – 138ºC
boiling pt = – 0.5ºC
Alkane
Side Chain
R – CH – CH – R
2
2
CH
2
R – CH – CH – R
2
2
# Carbons
Prefix
1
meth -
2
eth -
3
prop -
4
but -
5
pent -
6
hex -
7
hept -
8
oct -
9
non -
10
dec -
-ane
-yl
Alkane Melting & Boiling Temperatures
Room Temp.
Alkanes
• Generally unreactive
• Are able to undergo Combustion Reaction
Hydrocarbon + O2
→ CO2 + H2O
CH3CH2CH3
→ 3CO2 + 4H2O
+ 5O2
(propane)
CH3(CH2)6CH3 +
23/
2O2
→ 8CO2 + 9H2O
(octane)
• Same reaction if burning fuel in lab or burning food
inside body
Cyclic Alkanes
CH2 – CH2
CH2
CH2
CH2 – CH2
… same as …
Cyclohexane
CH3
Br
CH3
1,2 - dimethylcyclohexane
bromocyclobutane
Halogens
• Can only form 1 bond – similar to Hydrogens
• Name as a side chain – with “-o” at end of halogen
- provide position on parent chain
- included in alphabetical order of side chains
Br
CH3 - CH – CH3
Cl CH2CH3
CH3 - C – CH ‒ CH2 ‒ CH3
F
2-bromopropane
Cl
2,3-dichloro-3-ethyl-2-fluoropentane
Alkane
R – CH – CH – R
2
2
-ane
Alkene
R – CH = CH – R
-ene
Alkyne
R – C
-yne
C– R
CH
Side Chain
Halogen
-yl
2
R – CH – CH – R
2
2
Br
(e.g. methyl)
R – CH – CH – R
2
2
(e.g. bromo-)
-o
# Carbons
Prefix
# Carbons
Prefix
1
meth -
6
hex -
2
eth -
7
hept -
3
prop -
8
oct -
4
but -
9
non -
5
pent -
10
dec -
Alkenes
Carbon double bond(s)
• Name parent chain
- Determine number of carbons for prefix
- Suffix is “-ene”
• Specify position of starting point for double bond
- Double bond number takes priority over
side chains regarding numbers
- I.e. which end of chain is closest to double bd?
CH3
CH2 = CH-CH2-CH3
1-butene
CH3-CH-CH2-CH2-CH = CH-CH2-CH3
7-methyl-3-octene
Alkynes
Carbon double bond(s)
• Name parent chain
- Determine number of carbons for prefix
- Suffix is “-yne”
• Specify position of starting point for triple bond
CH
C-CH2-CH3
1-butyne
CH CH
ethyne
(acetylene)
Alkene Cis/Trans Isomers
• Double bonds remain fixed in space (do not rotate)
• IF (and a big if) groups at each end are different
THEN specify arrangement around bond
CIS
= groups same top or bottom side of bond
TRANS = groups opposite top or bottom side of bond
no
difference
CH3
H
CH3
C=C
H
cis-2-butene
CH3
H
CH3
C=C
H
trans-2-butene
CH3
H
CH3
C=C
CH3
NO Cis/Trans
isomerism
Alkenes: Typical Reactions
• Hydrogenation: add H2 across double bond
H
H
CH2 = CH-CH3
• Hydration:
+
H2
→
CH2 ‒ CH-CH3
add H2O across double bond
OH
CH2 = CH-CH3
• Halogenation:
+
H2O
→
CH2 ‒ CH-CH3
add (Halogen)2 across double bond
Br
CH2 = CH-CH3
H
+
Br2
→
Br
CH2 ‒ CH-CH3