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FUNCTIONAL GROUPS
FUNCTIONAL GROUPS
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Functional Groups
Atomic configurations called functional
groups, which have decisive influence on
the chemical and physical characteristics
of the compound; thus those containing
the same atomic formations have similar
characteristics, which may be: miscibility
with water, acidity/alkalinity, chemical
reactivity, and oxidation resistance.
Organic Acids-Carboxyl Groups
• Organic acids are characterized by the
functional group R-COOH, where R
literally means, “the rest of the compound”.
The carbon involved has one double
bonded oxygen and a single bonded
hydrogen which is also bonded to a
hydrogen.
Carboxyl Group
Because the carbon compound is polar
covalent, electrons are not shared equally.
This means that the Hydrogen atom is
able to be pulled away from the
compound, creating a proton, or acid, as
shown here.
Organic Acids
Note two things:
1. The functional group of
COOH, the acid carboxyl
group.
2. How the formula is written.
Amino Acids-note carboxyl group
Carboxyl Groups
Simple Alcohols
Alcohols have the functional group –OH and
are usually designated R-OH. One might
think that they are a base, however, you
have to remember that they are covalently
bonded, so they do not form ions. Bases
form ions.
Note the –OH group attached to the
carbon. This substance would be
methyl alcohol since it contains one
carbon. The formula would be
written as CH3OH.
Properties of Alcohols
The simplest and most commonly used alcohols
are methanol and ethanol. Methanol was
formerly obtained by the distillation of wood and
called "wood alcohol." It is now a cheap
commodity, the chemical product of carbon
monoxide reacting with hydrogen under high
pressure. Methanol is intoxicating but not
directly poisonous. It is toxic by its breakdown
(toxication) by the enzyme alcohol
dehydrogenase in the liver by forming formic
acid and formaldehyde which cause permanent
blindness by destruction of the optic nerve
Alcohols
Apart from its familiar role in alcoholic
beverages, ethanol is also used as a
highly controlled industrial solvent and raw
material. To avoid the high taxes on
ethanol for consumption, additives are
added to make it unpalatable (such as
denatonium benzoate — "Bitrex") or
poisonous (such as methanol). Ethanol in
this form is known generally as denatured
alcohol.
Alcohols (OH helps it dissolve)
Methanol, ethanol, and propanol are
miscible in water because the hydroxyl
group wins out over the short carbon
chain. Butanol, with a four-carbon chain, is
moderately soluble because of a balance
between the two trends. Alcohols of five or
more carbons (Pentanol and higher) are
effectively insoluble in water because of
the hydrocarbon chain's dominance.
Aldehydes
• An aldehyde is an organic compound
containing a terminal carbonyl group. This
functional group, which consists of a
carbon atom bonded to a hydrogen atom
and double-bonded to an oxygen atom
(chemical formula O=CH-), is called the
aldehyde group.
• The word aldehyde seems to have arisen
from alcohol dehydrogenated.
Aldehyde Group
Missing Oxygen
Notice the difference between the aledhyde
group and the carboxyl group. Here you should
see that the oxygen is missing from the carboxyl
group. This gives the compound a totally new set
of properites.
Uses of Aldehydes
Because of their high chemical
reactivity, aldehydes are important
intermediates for the manufacture of
resins, plasticizers, solvents, dyes,
and pharmaceuticals.
Ketone Structure
Notice here that a ketone is an organic compound with a
carbon that contains a DOUBLE BONDED OXYGEN ATOM.
This carbon is then bonded to two other carbon atoms.
Uses of Ketones
Ketones are often used in perfumes and
paints to stabilize the other ingredients so
that they don't degrade as quickly over
time. Other uses are as solvents and
intermediates in chemical industry.
Examples of ketones are acetone,
acetophenone, and methyl ethyl ketone.
Ketones and Your Body
• If you starve for more than a few hours, then the body will run out of
glucose (sugar) stores and will switch to breaking down fats and
produce 'ketones'. Ketones smell like pear drops and are found in
your breath and urine, which is how the body tries to get rid of them.
A build up of Ketones in the blood will result in the symptoms that
may include a breath odor resembling the smell of fruit.
• Insulin is important as it acts as a 'key' to allow sugar to move from
the blood into the cells, if you have diabetes and do not have
enough insulin then the body behaves as if it has run out of glucose
and switches to breaking down fats resulting in ketones.
• If this is unrecognised, it can lead to 'diabetic ketoacidosis' (DKA)
where you will feel very thirsty, start breathing fast and become very
dry and vomit profusely.
Esters
Properties of Esters
Esters, often have a pleasant smell and are
found in perfumes, essential oils, and
pheromones, and give many fruits their
scent.
Many esters have distinctive odors, which
has led to their use as artificial flavorings
and fragrances. See next slide.
Ethyl cinnamate
cinnamon
Ethyl lactate
butter, cream
Ethyl pentanoate
apple
Methyl acetate
Ethyl acetate
peppermint
nail polish remover, model paint, model airplane
glue
Ethers
Properties/Uses
Ethers are used as anesthetics.
The first surgical anesthetic use of ether is
credited to Dr. Crawford Williamson Long,
MD, age 27, of Jefferson, Georgia. On
March 30, 1842, he removed one of the
two tumors from the neck of Mr. James
Venable under ether anesthesia.
AROMATIC COMPOUNDS
AROMATIC COMPOUNDS
• Aromatic compounds derive their names from the fact
that many of these compounds in the early days of
discovery were grouped because they were oils with
fragrant odors, hence the name aromatic.
• The current definition of aromatic compounds includes
only those with a benzene ring, which is a special six
carbon ring compound with three alternating double
bonds. This structure imparts unique properties to
benzene which are different from other ring compounds.
See the benzene structure on the left.
• All aromatic hydrocarbons both benzenoid
and non-benzenoid are resonance
stabilized. They are water insoluble. They
are also carcinogenic (cancer forming) if
exposed with sufficient concentration and
exposure time. Most have a sweet aroma
hence the reason for the name "aromatic".
PROBLEM
• Benzene represents a special problem in that, to
account for all the bonds, there must be
alternating double carbon bonds:
• One representation is that the structure exists as
a superposition of so-called resonance
structures, rather than either form individually.
• This delocalisation of electrons is known as
aromaticity, and gives benzene great stability.
Benzene C6H6
Notice that in each structure of Benzene the double bonds
have shifted over one carbon. Since the bond shifts so
rapidly, both structures essentially exist at the same time.
To illustrate a moving bond, scientists represent this
moving bond as a circle (next slide).
BENZENE
RING STRUCTURES
BENZENE C6H6
CARBOMER
FULLERINES
• Fullerenes (Fig 4) are
an exciting new
classification of
aromatic organic
molecules that consist
of pure carbon. The
formula for Fullerenes
are either C60 or
C70.
Review of Functional Groups
• Try to draw the group.
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Alcohol
Acids
Benzene
Esters
Ether
Aldehydes
Ketones