Organic chemistry
The carbon compounds
Prof. Paola Valentinis
2^A- 2^B
Scholastic year 2006/07
Glossary
Sweeteners
Theory
Laboratory
Mysterious
Soaps
Fibres
Term
Phenomena
Chemist
inorganic
Coal
Organic
Combustion
Rocks
plants
Organic chemistry
Fill in the blanks using the new words
Organic chemistry was the term applied originally to the study of
substances connected directly with animals and plants, so it is derived
from the word “organism”. For this reason it received the name organic.
Such substances were thought to contain a mysterius vital force wich
made it impossible for man to prepare them from inorganic ingredients.
But in 1828 the German chemist Friedrich Wohler attempted to prepare
crystals of the inorganic salt ammonyum cyanate by evaporating its
solution . Istead, he obtained crystals of urea an organic subtance already
known for 50 years an the main constituent of urine. Over the following
years further organic substances were prepared in the laboratory and
eventually the vital force theory was abandoned.
Today the study of organic chemistry is very important because it help us
to understand the phenomena living in the world. Synthetic fibres, plastic,
medicines, artificial sweeteners are product of industrial organic chemistry
and the energy that man uses in every industrial activity derives mainly
from the combustion of organic material found in coal an crude oil.
carbon
Even though organic chemistry
focuses on compounds that contain
carbon and hydrogen, more than 95%
of the compounds that have isolated
from natural sources or synthesized in
the laboratory are organic.
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The special role of carbon in the chemistry of
the elements is the result of a combination of
factors, including the number of valence
electrons on a neutral carbon atom, the
electronegativity of carbon, and the atomic
radius of carbon atoms (see the table below).
The Physical Properties of Carbon
Electronic configuration 1s2 2s2 2p2
Electronegativity 2.55 Covalent radius 0.077
nm
Carbon has four valence electrons 2s2 2p2
and it must either gain four electrons or lose
four electrons to reach a rare-gas configuration.
The electronegativity of carbon is too small for
carbon to gain electrons from most elements to
form C4- ions, and too large for carbon to lose
electrons to form C4+ ions. Carbon therefore
forms covalent bonds with a large number of
other elements, including the hydrogen,
nitrogen, oxygen, phosphorus, and sulfur found
in living systems.
Because they are relatively small, carbon
atoms can come close enough together to form
strong C=C double bonds or even C C triple
bonds. Carbon also forms strong double and
triple bonds to nitrogen and oxygen. It can even
form double bonds to elements such as
phosphorus or sulfur that do not form double
bonds to themselves
Carbon and life
Several factors make carbon essential to life.
• The ease with which carbon atoms form bonds to
other carbon atoms.
• The strength of C-C single bonds and the covalent
bonds carbon forms to other non metals, such as
N, O, P, and S.
• The ability of carbon to form multiple bonds to
other non metals, including C, N, O, P, and S
atoms.
• These factors provide an almost infinite variety of
potential structures for organic compounds, such
as vitamin C shown in the figure below.
hydrocarbons
Compounds that contain only carbon and hydrogen are known as
hydrocarbons
• Those that contain as many hydrogen atoms as possible are said to be
saturated. The saturated hydrocarbons are also known as alkanes.
• Carbon not only forms the strong C C single bonds found in alkanes, it
also forms strong C=C double bonds. Compounds that contain C=C
double bonds were once known as olefins (literally, "to make an oil")
because they were hard to crystallize. (They tend to remain oily liquids
when cooled.) These compounds are now called alkenes.
• Alkenes are examples of unsaturated hydrocarbons because they
have fewer hydrogen atoms than the corresponding alkanes
Compounds that contain C C triple bonds are called alkynes. These compounds
have four less hydrogen atoms than the parent alkanes
Structure and Nomenclature of Hydrocarbons
The alkanes in the table above are all
straight-chain hydrocarbons, in
which the carbon atoms form a chain
that runs from one end of the
molecule to the other. The generic
formula for these compounds can be
understood by assuming that they
contain chains of CH2 groups with an
additional hydrogen atom capping
either end of the chain. Thus, for
every n carbon atoms there must be
2n + 2 hydrogen atoms: CnH2n+2.
Because an alkene can be thought of
as a derivative of an alkane from which
an H2 molecule has been removed, the
generic formula for an alkene with one
C=C double bond is CnH2n.
pollution
Hydrocarbons are a precursor to
ground-level ozone, a serious air pollutant in cities
across the United States. A key component of smog,
ground-level ozone is formed by reactions involving
hydrocarbons and nitrogen oxides in the presence of
sunlight. Hydrocarbon emissions result from incomplete
fuel combustion and from fuel evaporation. Today's cars
are equipped with emission controls designed to reduce
both exhaust and evaporative hydrocarbons.
Try yourself: synthetizes you an organic mixture
MAKING SOAP FROM OLIVE OIL
INGREDIENTS
125 cm3 of vegetable oil
100 cm3 of water
20 g of caustic soda (sodium hydroxide)
salt (if required)
essential oil or perfume (optional)
APPARATUS
safety goggles
beaker
glass rod
mould for setting soap
METHOD
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Weigh out your caustic soda onto a folded piece of paper. DO NOT TOUCH IT.
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Pour the oil and water into a big beaker and stir with a glass rod until you make an emulsion.
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Carefully add the caustic soda, slowly and stirring all the time. DON'T TOUCH IT !
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Keep stirring until a thick paste forms. This could take half an hour.
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If you still don't have a paste after half an hour, stir in 4 spatulas of salt.
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Add essential oil or perfume if you want.
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Pour into mould and leave to set for a few days.
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Keep your fingers crossed !
Lab- work
Write a purpose for the lab in you notebook. You might also wish to
think about the following questions. They will help you prepare for
the lab, but you need not turn them in at the beginning of class.
•What reaction is described by the word saponification. What are the
products from this reaction and what are the required reactants?
•Draw out the full structure for three of the carboxylic acids listed in books
table. Identify all of the polar bonds, and find the polar and non-polar regions
of the molecule.
•What is the most dangerous part of the lab?
•Why is it critical to clean up all spills immediately?
bibliography
GCSE chemistry
Complete Revision & Practice
Roggi- Picking
BIO-CHEM
Zanichelli
www. thinkQuest.org
www.chemed.chem.purdue.edu.html
Thanks for your attentions