AND COMPOUNDS OF CARBON (Назад на главную)
Organic chemistry is an extremely interesting field of natural science and of great
technological significance. The overwhelming majority of chemists prove to be
engaged in producing organic compounds; several millions being known so far.
In view of their obvious success in the manufacture of synthetic compounds, the
chemists are greatly interested in this field of science.
The name organic chemistry, which was originally used to refer to the chemistry
of substances that occur in living organisms, is now used for the chemistry of the
compounds of carbon. The chemistry of carbon was greatly advanced about a century
ago through the development of a general structure theory, this theory being a
chemical theory, induced from chemical facts.
In recent years it has received added verification through the determination of
exact structures of molecules and crystals by physical methods, especially X-ray
diffraction, electron diffraction, and the analysis of the spectra of substances.
During the first half of the 19th century many organic compounds were found to
have been obtained from plants and animals and also to have been made in the laboratory.
The were analyzed for their constituent elements, an their properties were
carefully studied. Efforts were made to find some correlation between the chemical
composition and the properties of the substances.
Elementary Carbon.Carbon occurs in nature in its elementary state in two
allotropic forms namely diamond, this being the hardest substance known, and
graphite, a soft, black crystalline substance used as a lubricant. Having investigated
all the substances thoroughly the scientists found charcoal, coke, and carbon black; to
be microcrystalline or amorphous (noncrystalline) forms of carbon.
Carbon burns to form gases: carbon monoxide CO, and carbon dioxide CO2, the
former being produced when there is a deficiency of oxygen or the flame temperature
is very high.
This investigation followed by others resulted in new discoveries in the field of
carbon. It has been found out that carbon monoxide is a colourless, odourless gas
with small solubility in water. It is poisonous, because of its ability to combine with
the hemoglobin in the blood in the same way that oxygen does, and thus to prevent
the hemolobin from combining with oxygen in the lungs and carrying it to the tissues.
It should be noted that the exhaust as from automobile engines contains some carbon.
Nevertheless carbon monoxide is a valuable industrial gas, for use as a fuel and as a
Carbon Dioxide.Carbon dioxide is a colourless, odourless gas with a weakly acid
taste, due to the formation of some carbonic acid when it is dissolved in water. It
appears to be about 50'/o heavier than air. It is easily soluble in water, one liter of
water at O'C dissolving 1,713 ml of the gas under 1 atm pressure. When crystalline
carbon dioxide is heated from a very low temperature its vapour pressure reaches 1
atm at 79' at which temperature it vaporizes without melting. If pressure were
increased to 2.5 atm the crystalline substance would melt to a liquid at 56.6'. Under
ordinary pressure, then, the solid substance could be changed directly to a gas.
Carbon dioxide is known to combine with water to form carbonic acid H2CO3 , it
being a weak acid.
If you studied all the properties more thoroughly you would see that carbon
dioxide is used for the manufacture of sodium carbonate, sodium hydrogen carbonate,
and carbonated water and for many other uses.
From this short review it's clear that chemistry of carbon and its compounds is a very
important field of chemistry and should be studied carefully.
Carbon PollutantsCarbon monoxide and carbon dioxide are both very important
atmospheric contaminants. Human activities are responsible for the introduction of
increasing quantities of these gases to the atmosphere. Carbon monoxide is
particularly important because of its potent mammalian toxicity, while carbon dioxide
is most significant because of its ability to regulate global temperature. Neither gas is
tought to causedirect damage to vegetation at ambient concentrations presently monitored.
Carbon monoxide has not been shown to produce acute effects on plants at
concentrations below 100 p.p.m. for exposures from one to three weeks. The
threshold of carbon dioxide toxicity to plants is in such excess of ambient conditions
as to be completely unimportant. The hypothesis that the increasing concentration of
carbon dioxide in the atmosphere might result in elevated global temperatures,
however, has enormous implications for the health of forest ecosystems.
Notes to the text:
3. to be engaged
4. so far
6. in view of
13. exhaust gas
15. to reduce
16. to damage
17. to prevent
18. to be responsible for
I. Answer the following questions:
1. What is organic chemistry. 2. Why are the scientists interested in the field of
organic chemistry. 3. What does the name organic chemistry refer to? 4. When was
the chemistry of carbon advanced'? 5. What phenomenon was found during the first
half of the 19th century. 6. Where does carbon occur? 7. In that form does carbon
occur in nature? 8. What gases does carbon form during its burning? 9. What
properties of ca-bon monoxide do you know? 10. What properties of carbon dioxide
do you know'? l l. What does carbon dioxide form combining with water? 12. What
are very important atmospheric contaminants?
II. Retell the text according to the following plan:
1. Organic chemistry.
2. The chemistry of carbon.
3. Elementary carbon,
4. The properties of carbon.
5. Carbon monoxide.
6. Carbon dioxide.
7. Carbon pollutants.
Date: 2015-12-17; view: 1106