Transcript Organic Chemistry

Organic Chemistry
Chapter 22
Organic Chemistry
The study of carbon-containing
compounds and their properties.
The vast majority of organic
compounds contain chains or rings
of carbon atoms.
Organic & Inorganic Compounds
Originally the distinction between inorganic
and organic substances was based on
whether or not they were produced by
living systems.
In 1828, German chemist Friedrich Wohler
prepared urea from the inorganic salt
ammonium cyanate by simple heating:
heat
NH4OCN ---> NH2CONH2
Hydrocarbons
. . . compounds composed of carbon and hydrogen.
Saturated: carbon-carbon bonds are all single alkanes [CnH2n+2]
H H
H C
C H
H H
Hydrocarbons
(continued)
Unsaturated: contains carbon-carbon
multiple bonds.
H H
H C
H
C
H
C
H
Hydrogen Addition
C2H4(g) + H2(g) ---> C2H6(g)
unsaturated
saturated
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H1s
H1s
sp3
sp3
sp3
H1s
C
sp3
H1s
The carbon-hydrogen bonds in methane.
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H
(a)
H
H
C
C
H
H
H
(b)
The Lewis structure, space-filling, and balland-stick models for ethane.
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(a)
(b)
The structures of propane and butane with 109.5o
bond angles.
Structural Isomerism
-- isomers contain the same atoms but one or
more different bonds.
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(a)
(b)
Normal butane (n-butane) and the branched
isomer, isobutane.
Isomers of Pentane
What are the three isomers of pentane?
1) n-pentane -- straight-chain
2) isopentane -- one branch from 2nd carbon
3) neopentane -- two branches from central
carbon
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CH3CH2CH2CH2CH3
n-Pentane
The straight-chain isomer, n-pentane.
Rules for Naming Alkanes
1. For alkanes beyond butane, add -ane to the
Greek root for the number of carbons.
C-C-C-C-C-C = hexane
2. Alkyl substituents: drop the -ane and add
-yl.
-C2H5 is ethyl
Rules for Naming Alkanes
3. Positions of substituent groups are specified
by numbering the longest chain sequentially.
C

C-C-C-C-C-C
3-methylhexane
4. Location and name are followed by root
alkane name. Substituents in alphabetical
order and use di-, tri-, etc.
See Sample Exercise 22.2 on pages 1062-1064.
Combustion Reactions of
Alkanes
C3H8(g) + 5O2(g) ----> 3CO2(g) + 4HOH(g)
2C4H10(g) + 13 O2(g) ----> 8CO2(g) + 10HOH(g)
Substitution Reactions
for Alkanes
Primarily where halogen atoms replace
hydrogen atoms.
CHCl3  Cl 2
h
CCl 4  HCl
Dehydrogenation Reactions
Cr2O3
CH3CH3 ----> CH2=CH2 + H2
500oC
ethane
ethylene
Cyclic Alkanes
Carbon atoms can form rings containing
only carbon-carbon single bonds.
C3H6, C4H8, C6H12
Shorthand notation for the cyclic alkanes.
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C
No "head-on"
overlap of
atomic orbitals
109.5
60
C
(a)
C
(b)
The molecular structure of cyclopropane and
the overlap of the sp3 orbitals that form the
C-C bonds.
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These two H
atoms repel
each other
Chair
Boat
(a)
(b)
The chair and boat forms of cyclohexane.
Alkenes and Alkynes
Alkenes: hydrocarbons that contain a carboncarbon double bond. [CnH2n]
CC=C
propene
Alkynes: hydrocarbons containing a carboncarbon triple bond. [CnH2n-2]
CCCCC
2-pentyne
Nomenclature for Alkenes
1. Root hydrocarbon name ends in -ene
C2H4 is ethene
2. With more than 3 carbons, double bond is
indicated by the lowest numbered carbon
atom in the bond.
C=CCC is 1-butene
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sp2
sp2
sp2
H1s
sp
2
sp2
C
C
sp2
H1s
2p
The bonding in ethylene.
The two stereoisomers of 2-butene.
a) cis-2-butene b) trans-2-butene
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H
H
H
H
C
H
C
H
The bonding in ethane allows rotation and no
cis-trans isomerism.
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2p
2p
2p
H1s
H1s
2p
H
C
H
C
sp
2p
2p
2p
sp
2p
The bonding in acetylene.
sp
Addition Reactions
. . . in which (weaker)  bonds are broken and
new (stronger)  bonds are formed to
atoms being added.
catalyst
CH2  CHCH3  H2  CH3CH2CH3
propene
propane
Halogenation
CH2=CHCH2CH2CH3 + Br2 --->
CH2BrCHBrCH2CH2CH3
1-pentene
1,2-dibromopentane
Aromatic Hydrocarbons
A special class of cyclic unsaturated hydrocarbons.
Cl
FeCl3

+ Cl2 
benzene
+ HCl
Chlorobenzene
Aromatic Hydrocarbons
phenyl group
Ortho (o-) -- two adjacent substituents.
meta (m-) -- two substituents with one
carbon between them.
para (p-) -- two substituents opposite each other.
Refinery Processes
Cracking: large molecules broken down to smaller
ones by breaking carbon-carbon bonds.
Pyrolysis (thermal cracking): The process that
produces cracking at high temperatures.
Catalytic Cracking: Cracking at lower
temperatures.
Catalytic reforming: Alkanes and cycloalkanes
converted to aromatic compounds.
The Common Functional Groups
Class
General Formula
Halohydrocarbons
RX
Alcohols
ROH
Ethers
ROR
O
R C H
Aldehydes
The Common Functional Groups
Class
Ketones
Carboxylic Acids
Esters
General Formula
O
R C R'
O
R C OH
O
R C O R'
Amines
RNH2
Amides
R-C=ONH2
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Table 22.5 The Common Functional Groups
Class
Functional
Group
Halohydrocarbons
X (F,Cl,Br,I)
RX
Alcohols
OH
ROH
Ethers
O
ROR'
O
O
Aldehydes
Ketones
Carboxylic acids
CH
General
Formula*
RCH
O
O
C
RCR'
O
O
COH
O
RCOH
O
Esters
CO
RCOR'
Amines
NH2
RNH2
*R and R' represent hydrocarbon fragments.
Example
CH3I
Iodomethane
(methyl iodide)
CH3OH
Methanol
(methyl alcohol)
CH3OCH3
Dimethyl ether
CH2O
Methanal
(formaldehyde)
CH3COCH3
Propanone
(dimethyl ketone
or acetone)
CH3COOH
Ethanoic acid
(acetic acid)
CH3COOCH2CH3
Ethyl acetate
CH3NH2
Aminomethane
(methylamine)
Alcohols
contain the hydroxyl group (-OH).
Aldehydes & Ketones
contain the carbonyl group ( C=O ).
In ketones the carbonyl group is bonded to
two carbon atoms -- CH3C=OCH3.
In aldehydes the carbonyl group is bonded to
at least one hydrogen atom -- HCHO.
Carboxylic Acids & Esters
Carboxylic acids contain the carboxyl group
O
(-C-OH).
O
Esters contain the -C-O- group.
Amines & Ethers
Amines contain -NH2 group.
If one hydrogen is removed and replaced with a
hydrocarbon group, it is a primary amine.
If two hydrogen are replaced, it is a secondary
amine.
If all three hydrogens are replaced, it is a
tertiary amine.
Ethers contain the -O- group.
Polymers
. . . are large, usually chainlike molecules that
are built from small molecules called
monomers.
Monomer
Ethylene
Vinyl chloride
Tetrafluoroethylene
Polymer
Polyethylene
Polyvinyl chloride
Teflon
Types of Polymerization
Addition Polymerization: monomers “add
together” to form the polymer, with no other
products. (Teflon)
Condensation Polymerization: A small
molecule, such as water, is formed for each
extension of the polymer chain. (Nylon)