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Aromatic Hydrocarbons
Aromatic structures are formally related to benzene.
The delocalized  electrons are usually represented as a
circle in the center of the ring.
Benzene is a planar symmetrical molecule.
Benzene is not reactive because of the stability associated
with the delocalized  electrons.
Most aromatic rings are given common names.
• Even though they contain  bonds, aromatic
hydrocarbons undergo substitution more readily than
addition (because of delocalization of  bonds).
• Example: if benzene is treated with nitric acid in the
presence of sulfuric acid (catalyst), nitrobenzene is
produced.
Functional Groups
• To get reactivity out of an organic molecule, functional
groups have to be added.
• Functional groups control how a molecule functions.
• More complicated functional groups contain elements
other than C or H (heteroatoms).
• Functional group containing molecules can either be
saturated (alcohols, ethers, amines etc.) or unsaturated
(carboxylic acids, esters, amides, etc.).
• We usually use R to represent alkyl groups (hydrocarbon).
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Alcohols (alkanols) (R-OH)
Alcohols are derived from hydrocarbons and contain -OH
groups.
The names are derived from the hydrocarbon name with ol replacing the e at the end of the -ane suffix. Example:
ethane becomes ethanol.
Since the O-H bond is polar, alcohols are more water
soluble than alkanes.
CH3OH, methanol, is used as a gasoline additive and a
fuel.
• Polyhydroxy alcohols (polyols) contain more than one OH group
per molecule (e.g. ethane-1,2-diol - ethylene glycol used as
antifreeze).
Primary Alcohol – The C on which the OH is
attached has only one other C atom directly
attached to it.
Secondary Alcohol – The C on which the OH is
attached has 2 other C atoms directly attached to it.
H
R
C
OH
R'
secondary alchol
Tertiary Alcohol – The C on which the OH is
attached has 3 other C atoms directly attached to it.
R''
R
C
OH
R'
tertiary alcohol
Naming Alcohols – Name like alkanes (count carbon
atoms, attach substituents), replace “e” with “ol.”
OH
= ethanol
Propan-2-ol
2-methylpropan-2-ol
propan-1,2,3-triol
Ethan-1,2-diol
Reactions of Alcohols
1. Complete combustion: C2H5OH + O2  CO2 + H2O
2. Oxidation – warmed with acidified potassium dichromate (Cr2O72-)
Primary alcohols
oxidized to aldehydes, then to carboxylic acids.
O
O
C
C
H
R
C
OH
R
H
R
OH
H
primary alcohol
aldehyde
carboxylic acid
To maximize aldehyde production, the product is distilled as it
is formed.
To maximize carboxylic acid production, the products are
heated under reflux for long periods.
Secondary alcohols (C with OH is attached to 2 other C)
oxidized to ketones
H
R
C
O
OH
C
R
R'
secondary alcohol
R'
ketone
Tertiary alcohols (C with OH is attached to 3 other C – no H atoms
attached to C with OH)
cannot be oxidized by dichromate
2.
Dehydration (in concentrated sulfuric or phosphoric acid) –
produces a double bond (opposite of addition of water)
H
OH
C
C
alcohol
C
C
alkene
Ethers (R-O-R′)
• Compounds in which two hydrocarbons linked by an
oxygen are called ethers.
• Ethers are commonly used as solvents.
O
= ethoxyethane
or diethyl ether
Compounds with a
Carbonyl Group
Aldehydes and Ketones
• The carbonyl functional group is C=O.
• Aldehydes (alkanals) must have at least one H atom
O
attached to the carbonyl group:
R
H
• Ketones (alkanones) must have two C atoms attached to
the carbonyl group:
O
R
R'
• Aldehydes and ketones are prepared from the oxidation
of alcohols.
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Named as alkanes with “-al” (aldehydes) or “-one” (ketones)
added to the end. The carbon on which the oxygen is attached
is numbered.
Examples
O
1.
propanone
O
2.
ethanal
3.
O
heptan-3-one