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

reducing agent.

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.

II

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:

1. overwhelming

2. majority

3. to be engaged

4. so far

6. in view of

7. recent

8. verification

9. correlation

10. lubricant

11. carbon

12. poisonous

13. exhaust gas

14. valuable

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