Organic Chemistry is:
Organic Chemistry
The study of the nonmineral (mineral being CO, CO2, etc.) compounds of
carbon.
Out of over 10million known compounds, about 9million are carbon compounds
and thousands of new ones are reported every year.
The variety of organic compounds comes from:
a. The stability of chains of carbon atoms (covalently bonded)
b. The occurrence of isomers (different arrangements of the same number and
types of atoms)
c. the variety of functional groups (“add-on” groups of atoms)
Originally named “organic” because these molecules were associated with
living systems and were considered to contain a “vital force” from God that
could not be reproduced in the lab.
Recall that from the Lewis dot structure that carbon has
four valence electrons and is capable of forming four
covalent bonds
The first organic molecule synthesized in the lab was Urea, by Friedrich Wöhler
in 1828.
O
||
NH4OCN(aq) + heat → H2N-C-NH2
Ammonium cyanate
(Inorganic salt)
Urea
(Organic)
The simplest type of organic molecules are known as
hydrocarbons. They consist of only carbon and hydrogen.
These are broken down into three sub-catagories:
Alkanes (ane suffix in the name): containing only single
bonds between the carbons. Also known as saturated
hydrocarbons because they contain as many hydrogen
atoms as possible.
Space filling
model
Alkenes (ene suffix in the name): containing at least one
double bond between carbons.
Alkynes (yne suffix in the name): containing at least one
triple bond between carbons.
Perspective
diagram
Geometry:
Tetrahedral
Ball and stick model
Ways of representing the structure of hydrocarbons
1
If hydrogens are not
explicitly shown, it is
known as a skeletal
structure
The name of the
hydrocarbon is
based on the
number of
carbons in the
chain. Can you
identify a general
formula for
alkanes?
Note the different types of formulas and what information they give
Question: Name this hydrocarbon and write its molecular and
condensed structural formula.
Answer:
Octane
C8H18
CH3CH2CH2CH2CH2CH2CH2CH3 or
CH3(CH2)6CH3
Many hydrocarbons have branches (also known as substituents or alkyl
groups) coming off of their main “parent chain”.
Compounds that have the same molecular formula, but different structures are
known as structural isomers.
The rules (nomenclature) for naming these types of compounds (branchedchain alkanes) requires a series of steps.
1. Find the longest continuous chain of hydrocarbon (remember that they may bend
around corners). This is your parent chain.
2. Number the parent chain beginning from the end closest to the first branch.
3. Identify the alkyl groups and the carbon number on the parent chain they are
attached to.
4. List the alkyl groups in alphabetical order and the number where the attachment
occurs. (Separate numbers from words with hyphens).
5. Finally, list the parent name.
Example:
4-ethyl-2-methylhexane NOT 3-ethyl-5-methylhexane
2
Note that it doesn’t matter if the parent chain “bends”
around corners.
If there are more than one of the same type of alkyl
group, the prefixes di, tri, tetra, etc. must be used. These
are not used when alphabetizing.
Examples:
Name the
following
molecules
H
If more than one branch occurs on the same parent
carbon, the number must be listed each time with a
comma in-between numbers.
3C
CH
H
CH
3C
2
CH
H
3
3
CH
3
HC
C
Answers:
Problems:
a. n-pentane
Draw the following structures:
b. 2-methylbutane
a) n-butane
c. 2,4,5-trimethylhexane
b) 4-propyloctane
d. 3,3-dimethylpentane
CH
c) 4-ethyl-2-methylhexane
d) 2,2,3,3-tetramethylbutane
C-C-C
Isopropyl
|
C-C-C-C
Iso is used in alphabetizing but sec
and tert are not.
sec-butyl
|
C
|
C-C
|
Isobutyl
C
|
C
|
C-C-C
tert-butyl (tertiary)
|
The line on each substituent indicates where it attaches to the parent chain.
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Name this structure:
H3C
H3C
H3C
H3C
H3C
H3C
CH3
H3C
CH3
CH3
H3C
CH3
4-tert-butyl-2-methyloctane
H3C
CH3
H3C
CH3
CH3
H3C
CH3
CH3
H3C
CH3
Name this structure:
CH3
CH3
4-ethyl-3-isopropyl-2-methylhexane
Cycloalkanes
CH3
Sometimes carbon molecules form rings. Single bonded rings are
known as cycloalkanes. In naming them:
1. If it is a simple ring without any substituents simply name the
compound with the word cyclo in front of it.
2. If substituents exist on the ring structure, number the ring
carbons in such a way as to create the smallest number(s) for
branch locations:
CH3
Example: Name this compound
H3C
4
CH3
H3C
CH3
CH3
1-ethyl-2-isopropylcyclopentane
Example: Name this compound
CH3
H3C
Draw the structure for:
H3C
2-ethyl-1-methyl-4-propylcyclohexane
CH3
1-isobutyl-3-methylcyclobutane
CH3
CH3
Alkene and alkyne nomenclature:
Naming compounds with multiple bonds is similar to
alkanes but with a few very important exceptions.
H3C
1. The parent chain is the longest continuous chain of
carbons containing all the multiple bonds.
2. Begin numbering the parent chain from the end
closest to the first multiple bond (if it is the same then
go to the next double or triple bond)
3. The name must indicate the quantity and location
of the multiple bond(s).
CH3
5
Because of the potential continuation of a carbon chain on either side of a
double bond, sometimes the prefixes “cis” and “trans” must be used to
identify which form is being referred to:
Draw the structure for
3,4-dichloro-9-methyltrans-dec-3-ene
Example:
H
H3C
C
CH3
trans-pent-2-ene
(trans-2-pentene)
H
cis-pent-2-ene
(cis-2-pentene)
C
H
H
H3C
C
C
CH3
H3C
H3C
CH3
Cl
CH3
H3C
Cl
CH3
CH3
CH3
CH3
Example: Name this structure.
Name this compound:
H3C
H3C
H3C
CH3
CH3
CH3
H3C
CH2
CH3
4-ethyl-2,3,6-trimethylhept-2-ene
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3-ethylpenta-1,2-diene
Name this structure:
H3C
CH2
H3C
CH2
2-hexylbuta-1,3-diene
(aka 3-methylenenon-1-ene)
H2C
CH3
Draw the structure for:
7-ethyl-4-methylnona-2,5-diyne
CH2
H2C
CH3
Name this structure:
CH3
H3C
CH3
H3C
CH3
H3C
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Alkane
CnH2n+2
sp3 hybridization (109.5o)
tetrahedral
3,4-dimethylcyclopentene
Alkene
CnH2n
sp2 hybridization (120o)
trigonal planar
Alkyne
CnH2n-2
sp hybridization (180o)
linear
Petroleum Refinery
Octane Rating
Scale from 0 to 100 that measures the anti-knock (pre-ignition) properties of
different types of hydrocarbons used for gasoline.
0 = n-heptane
100 = 2,2,4-trimethylpentane (a.k.a. isooctane)
Generally, the more branches a hydrocarbon has, the better its anti-knock
properties.
The old regular “leaded” gasoline used to contain tetraethyllead (T.E.L) as a
means to improve anti-knock properties without having to refine the gasoline
as much through catalytic cracking (Chemically breaking long
hydrocarbons up and reassembling them as shorter chains with branches).
Fractional
distillation towers
typically range in
height from 12 to
30 meters
Catalytic converters use chemical catalysts at high temperatures to combust
CH3
unburned hydrocarbons.
H2C
CH2
H3C
Pb
CH2
CH3
H2C
CH3
Common Functional
Groups:
You should learn to recognize
these groups.
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Identify the functional groups on this molecule:
CH2
H
OH
C
H
C
C
H
H
O
H
C
H
C
H
C
H
Identify the functional groups on this molecule:
H
O
Identify the functional groups on this molecule:
Alcohol
Alkene
O
CH2
Ether
H
OH
C
H
C
C
H
H
O
H
H
C
H
H
C
O
H
C
H
O
H
H
Ketone
H
C
H
H
N
O
H
H
C
C
C
H
C
O
H
C
H
Identify the functional groups on this molecule:
Draw the structures for:
a. methylpropylether
Carboxylic Acid
b. 4-methyl-3-hexanone
Ester
O
c. methyl butanoate
C
O
H
C
H
O
H
C
O
H
H
H
C
H
N
H
H
C
H
C
H
Amine
9
Ester Synthesis:
Draw the structures for:
O
a. methylpropylether
H3C
b. 4-methyl-3-hexanone
The ester functional group is associated with many aromas and flavors. They
can be synthesized to produce artificial smells and flavors
CH3
c. methyl butanoate
Esters are formed through a condensation reaction between alcohols and
carboxylic acids using a catalyst such as H2SO4.
O
Alcohol + Carboxylic acid → Water + Ester
H3C
CH3
CH3
O
H3C
O
CH3
Aromatic Hydrocarbons (containing the benzene ring)
Example:
O
Structure originally determined by August Kekulé (1865)
+
H3C
Hydrocarbon chains that do not contain the benzene ring are known as
aliphatic.
CH3
HO
OH
Or
Propanol (propyl alcohol)
butanoic acid (butyric acid)
O
H2O
+
CH3
H3C
Structure has delocalized p-orbital electrons
O
Propylbutanoate (propylbutyrate)
Water
Note: The water is formed from the H of the carboxylic acid and the OH of
the alcohol.
In naming the ester, the portion of the hydrocarbon chain that came from the
alcohol is listed first in the name.
Alkyl-substituted benzenes are sometimes referred to as arenes. If the alkyl group has
less than six carbons, it is named as a substituted benzene, otherwise the benzene ring
is considered the substituent and is called a phenyl (fen’-nil) group.
On a compound such as xylene (see below) the terms ortho, meta and para
are used to indicate the relative positions of the methyl group substituents on
the benzene ring.
CH 3
Some benzene containing compounds have special trivial names. For instance:
CH 3
Toluene
Phenol
Analine
CH 3
H 3C
CH 3
OH
H 3C
H 3C
NH 2
The point of attachment for these compounds is always considered carbon 1 when
numbering the ring.
Ortho-Xylene
(o-Xylene)
(1,2-dimethylbenzene)
Meta-Xylene
(m-Xylene)
(1,3-dimethylbenzene)
Para-Xylene
(p-Xylene)
(1,4-dimethylbenzene)
10
Absorption and conversion of
light energy in plants.
Organic Molecules:
Tylenol: The words acetaminophen and
paracetamol both come from the chemical name
for the compound, N-acetyl-para-aminophenol (or
para-acetyl-amino-phenol): N-acetyl-paraaminophenol and para-acetyl-amino-phenol.
Caffeine, C8H9O2N4
C27H45OH
Hemoglobin
Cis and trans fatty acid molecules
C2952H4664N812O832S8Fe4
OH
Pseudoephedrine
NH
CH3
CH3
benz(a)anthracene: Found in charred
meat from barbecue grill. Carcinogen.
NH
Ibuprofen
CH3
Methamphetamine
CH3
Naphthalene (Moth balls)
Antifreeze
Organic Reactions
Hydrogenation (an addition reaction):
Hydrogenation of a C=C bond on a
catalyst:
(1) The reactants have adsorbed to the
catalyst's surface and H2 has dissociated.
(2) An H atom binds to one of the C
atoms. The other C atom is bound to the
surface.
(3) The second C atom binds to an H
atom. The molecule leaves the surface.
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Polymers:
Oxidation reactions with alcohols:
Reactive Dyes:
Fiber reactive dye is the most
permanent of all dye types. Unlike
other dyes, it actually forms a
covalent bond with the cellulose or
protein molecule. Once the bond is
formed, what you have is one
molecule, as the dye molecule has
become an actual part of the
cellulose fiber molecule.
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