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HYDROCARBONS
These are compounds composed of carbon and hydrogen. They are generally insoluble in water although those with lighter molecular masses are gases and are slightly soluble. Examples of hydrocarbons include methane – the gas we burn as natural gas, propane (also called liquid petroleum gas) and petroleum jelly.
Hydrocarbons with single carbon-carbon bonds are referred to as being saturated whilst any hydrocarbon that contains a double bond is said to be unsaturated.
Saturated hydrocarbons are also called the alkanes, whilst the unsaturated hydrocarbons include both those molecules that contain carbon-carbon double bonds (referred to as the alkenes) and those that contain carbon-carbon triple bonds (referred to as the alkynes).
Alkanes and alkenes are natural products that have resulted from the decay of organiccompounds from plants and animals that lived millions of years ago. They are found today as petroleum, which are mixtures of hydrocarbons containing up to 30 or 40 carbon atoms. Different components of petroleum can be isolated by fractional distillation.
These hydrocarbons are good sources of fuels, the so-called „fossil fuels‟. As mentioned previously, the global production of such fossil fuels is 3 billion tonnes. As they are produced in such large quantities, pollution of the environment with these fossil fuels is of concern. The major route of entry into the environment isn‟t through spectacular disasters such as the oil spills from ships, but rather through our daily activities. Pumping fuel into cars, and oil spilled onto the road as a result of old faulty cars are major contributors.
ALKANES
This family of compounds consists of substances that contain only carbon and hydrogen joined by single bonds. They obey the general formula
CnH2n + 2
Thus if an alkane has six carbons, its formula will be C6H14. The simplest alkane is methane, CH4. Methane is also the most abundant organic species in the atmosphere. It is produced mainly by organisms breaking down organic material in places such as marshes, lake bottoms, land fills and the stomach of ruminant animals. Reactions of Alkanes
Because they are saturated compounds and because the C-C and C-H bonds are relatively strong, the alkanes are fairly unreactive, (e.g. at room temperature they do not react with acids, bases, or strong oxidising agents) which makes them invaluable as lubricants and the backbone of plastics.
At sufficiently high temperatures, alkanes react vigorously with oxygen. This is known as a combustion reaction and is the basis for their widespread use as fuels. An example is the reaction of butane with oxygen. The production of carbon dioxide in the environment is of concern because it has been implicated in the green house effect. Animals and plants produce carbon dioxide. Recently there has been an increase in carbon dioxide production brought about by a combination of deforestation and the burning of fossil fuels. (Plants use up carbon dioxide in photosynthesis, so removing vegetation is a good way to increase the amounts of carbon dioxide in the atmosphere). Carbon dioxide is thought to act like a blanket placed over the earth, it captures infrared radiation and transforms it into heat (The so-called “Green House Effect”). This may lead to an increase in the earth‟s temperature, which may cause a melting of the earth‟s ice caps. This could have potentially devastating effects, particularly for people who live in seaside cities.
Alkanes also under-go reactions induced by UV light. Examples include the slowbreakdown of plastics in the sun, and halogenation reactions (reactions where halogen atoms such as Cl, Br, or I replace H in the molecule).
These are compounds composed of carbon and hydrogen. They are generally insoluble in water although those with lighter molecular masses are gases and are slightly soluble. Examples of hydrocarbons include methane – the gas we burn as natural gas, propane (also called liquid petroleum gas) and petroleum jelly.
Hydrocarbons with single carbon-carbon bonds are referred to as being saturated whilst any hydrocarbon that contains a double bond is said to be unsaturated.
Saturated hydrocarbons are also called the alkanes, whilst the unsaturated hydrocarbons include both those molecules that contain carbon-carbon double bonds (referred to as the alkenes) and those that contain carbon-carbon triple bonds (referred to as the alkynes).
Alkanes and alkenes are natural products that have resulted from the decay of organiccompounds from plants and animals that lived millions of years ago. They are found today as petroleum, which are mixtures of hydrocarbons containing up to 30 or 40 carbon atoms. Different components of petroleum can be isolated by fractional distillation.
These hydrocarbons are good sources of fuels, the so-called „fossil fuels‟. As mentioned previously, the global production of such fossil fuels is 3 billion tonnes. As they are produced in such large quantities, pollution of the environment with these fossil fuels is of concern. The major route of entry into the environment isn‟t through spectacular disasters such as the oil spills from ships, but rather through our daily activities. Pumping fuel into cars, and oil spilled onto the road as a result of old faulty cars are major contributors.
ALKANES
This family of compounds consists of substances that contain only carbon and hydrogen joined by single bonds. They obey the general formula
CnH2n + 2
Thus if an alkane has six carbons, its formula will be C6H14. The simplest alkane is methane, CH4. Methane is also the most abundant organic species in the atmosphere. It is produced mainly by organisms breaking down organic material in places such as marshes, lake bottoms, land fills and the stomach of ruminant animals. Reactions of Alkanes
Because they are saturated compounds and because the C-C and C-H bonds are relatively strong, the alkanes are fairly unreactive, (e.g. at room temperature they do not react with acids, bases, or strong oxidising agents) which makes them invaluable as lubricants and the backbone of plastics.
At sufficiently high temperatures, alkanes react vigorously with oxygen. This is known as a combustion reaction and is the basis for their widespread use as fuels. An example is the reaction of butane with oxygen. The production of carbon dioxide in the environment is of concern because it has been implicated in the green house effect. Animals and plants produce carbon dioxide. Recently there has been an increase in carbon dioxide production brought about by a combination of deforestation and the burning of fossil fuels. (Plants use up carbon dioxide in photosynthesis, so removing vegetation is a good way to increase the amounts of carbon dioxide in the atmosphere). Carbon dioxide is thought to act like a blanket placed over the earth, it captures infrared radiation and transforms it into heat (The so-called “Green House Effect”). This may lead to an increase in the earth‟s temperature, which may cause a melting of the earth‟s ice caps. This could have potentially devastating effects, particularly for people who live in seaside cities.
Alkanes also under-go reactions induced by UV light. Examples include the slowbreakdown of plastics in the sun, and halogenation reactions (reactions where halogen atoms such as Cl, Br, or I replace H in the molecule).