Laboratory‎ > ‎ Hydrocarbons

INTRODUCTION

The aim of this experiment is classified of the hydrocarbon and learn the test which are aromatic bromation, permanganate test, sulfuric acid test and nitration of aromatic hydrocarbon. Hydrocarbon , any organic compound composed solely of the elements hydrogen and carbon. The hydrocarbons differ both in the total number of carbon and hydrogen atoms in their molecules and in the proportion of hydrogen to carbon. The hydrocarbons can be divided into various homologous series. Each member of such a series shows a definite relationship in its structural formula to the members preceding and following it, and there is generally some regularity in changes in physical properties of successive members of a series.The alkanes are a homologous series of saturated aliphatic hydrocarbons. The first and simplest member of this series is methane, CH4; the series is sometimes called the methane series. Each successive member of a homologous series of hydrocarbons has one more carbon and two more hydrogen atoms in its molecule than the preceding member. The second alkane is ethane, C2H6, and the third is propane, C3H8. Alkanes have the general formula CnH2n+2 (where n is an integer greater than or equal to 1).  Generally, hydrocarbons of low molecular weight, e.g., methane, ethane, and propane, are gases; those of intermediate molecular weight, e.g., hexane, heptane, and octane, are liquids; and those of high molecular weight, e.g., eicosane (C20H42) and polyethylene, are solids. Paraffin is a mixture of high-molecular-weight alkanes; the alkanes are sometimes called the paraffin series. Other homologous series of hydrocarbons include the alkenes and the alkynes. The various alkyl derivatives of benzeneare sometimes referred to as the benzene series. Many common natural substances, e.g., natural gas, petroleum, and asphalt, are complex mixtures of hydrocarbons. The coal tar obtained from coal by coking is also a mixture of hydrocarbons. Natural gas, petroleum, and coal tar are important sources of many hydrocarbons. These complex mixtures can be refined into simpler mixtures or pure substances by fractional distillation. During the refining of petroleum, one kind of hydrocarbon is often converted to another, more useful kind by cracking. Useful hydrocarbon mixtures include cooking gas, gasoline, naphtha, benzine, kerosene, paraffin, and lubricating oils. Many hydrocarbons are useful as fuels; they burn in air to form carbon dioxide and water.  The hydrocarbons differ in chemical activity. The alkanes are unaffected by many common reagents, while the alkenes and alkynes are much more reactive, as a result of the presence of unsaturation (i.e., a carbon-carbon double or triple bond) in their molecules. Many important compounds are derived from hydrocarbons, either by substitution or replacement by some other chemical group or element of one or more of the hydrogen atoms of the hydrocarbon molecule, or by the addition of some element or group to a double or triple bond (in an unsaturated hydrocarbon). Such derivatives include alcohols, aldehydes, ethers, carboxylic acids, and halocarbons.

MATERIALS

Test tubes, water bath, thermometer, pipette, benzene, bromine solution, iron fillings, potassium permanganate (KMnO4), acetone, paraffin, H2SO4, HNO3, distilled water.

PROCEDURE

Aromatic Bromation:

1 mL of benzene was placed into two seperate test tubes.2-3 drops of bromine solutions was added in each test tubes.A few iron fillings was added one of the benzene samples.Both tubes was placed in a warm-bath at 50°C for 30 minutes.

Permanganate Test:

0.5 mL of benzene was added to 3 mL of KMnO4 solution and it was shaked well.Then 0.1 g solid paraffin was dissolved in 1 mL alcohol free acetone in another test tube.Then permanganate solution was added drop by drop to the second solution.

Sulfuric Acid Test:

0.5 mL benzene was added to 3 mL of concentrated H2SO4 and this solution was shaked gently.

Nitration of aromatic Hydrocarbons:

Mixture of 1 mL HNO3 concentrated with two drops of concentrated H2SO4 was added to 1 mL of the benzene.solution was heated at 50°C of 15 minutes.And then 5 mL of water was poured into the solution.

RESUTS AND OBSERVATIONS

For the first test aomatic bromation,in each of the two test tube color change was occured.But test tube which is Fe in color change more rapidly.

For the permanaganate test, in first test tube two layer were occured.In second test tube two layer were occured to.Bottom layer’s color was dark,top layer’ color was light. For sulfuric acid test, hydrocarbon which is benzene didn’t dissolved in cocentrated H2SO4.Heat is evolved.

For nitration of aromatic hydrocarbons, two layers were occured.Heavy oil was the top layer.

DISCUSSION

In this experiment benzene and paraffin were used as hydrocarbon. Benzene, also known as benzol, is an organic chemical compound with the formula C6H6. It is sometimes abbreviated PhH. Benzene is a colorless and flammable liquid with a sweet smell and a relatively high melting point. It is carcinogenic and its use as additive in gasoline is now limited, but it is an important industrial solvent and precursor in the production of drugs, plastics, synthetic rubber, and dyes. Benzene is a natural constituent of crude oil, but it is usually synthesized from other compounds present in petroleum. Benzene is an aromatic hydrocarbon and the second [n]-annulene ([6]).

            Paraffin is a common name for a group of alkane hydrocarbons with the general formula CnH2n+2, where n is greater than about 20, discovered by Carl Reichenbach. It is distinct from the fuel known in Britain as paraffin oil or just paraffin, which is called kerosene in American English. Usage of the term varies in other countries, leading to confusion about which substance is being referred to. The solid forms of paraffin are called paraffin wax. Paraffin is also a technical name for an alkane in general, but in most cases it refers specifically to a linear, or normal alkane, while branched, or isoalkane are also called isoparaffins. The name is derived from the Latin parum (= barely) + affinis with the meaning here of “lacking affinity”, or “lacking reactivity”).

            In first test Fe was used as Lewis acid and addition of Lewis acid does cause a facile reaction for the generation of a positive bromine.Permanganate was used as oxidizing agent in second test.In nitration of aromatic hydrocarbon catalyst which is water was used.

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