ALKANES

What is a hydrocarbon ?
 Hydrocarbons Alkanes Formulas Stock Illustration - Download Image ...Around six million compounds of carbon are already known! Because there are so many, it is helpful to pick out those compounds which have similar structures. One of the simplest types of organic compound is the hydrocarbon.
      The hydrocarbons that we study at this level can be subdivided into two 'families'. Some hydrocarbons are saturated. These molecules contain only single covalent bonds between carbon atoms. Since carbon valency of 4, the bonds  not used in making the chain are linked of hydrogen atoms (see the figure top). No further atoms can be added to molecules of these compounds. This family of saturated hydrocarbons is known as the alkanes.
      Homologous Series: Definition,Properties and Characteristics ...
      Table up gives the names and formulae of the first six members of the series of alkanes. The simplest alkane contains one carbon atom and is called methane. Note that the names of the series of hydrocarbons all end in -ane. The first part of the name (the prefix) tells you the number of atoms in the chain. These prefixes are used consistently in naming organic compounds.
       The formulae given in table are the molecular formulae of the compounds. Each molecule increases by a -CH2- group as the chain gets longer (see the figure on top). Indeed, the formulae of long-chain alkanes can be written showing the number of -CH2- groups in the chain. For example, octane (C8H18) can be written as CH3--(CH2)6--CH3. The formulae of these molecules all fit the general formula CnH2n+2 (where n is the number of carbon atoms present).
       In organic chemistry, the structure of a molecule is also very important. Figure on the top shows the structural formulae of the first eight alkanes in the series. A structural formula shows the bonds between the atoms. As the length of the hydrocarbon chain increases, the strength of the weak forces between the molecules (intermolecular forces or van der Waals' forces) is increased. This shows itself in the increasing boiling points of the members of the series. The melting points and boiling points of the alkanes increase gradually. Under normal conditions, the first four members of the family are gases, and those between C5H12 and C16H34 (which in short are called C5 to C16 alkanes) are liquids. The compounds in the alkanes family with 17 or more carbon atoms are waxy solids.
         
      Every organic compound has three different formulae. The first of these is the empirical formula. This formulae is the simplest possible whole-number ratio of the atoms in a compound; thus for methane it is CH4, but for ethane it is CH3.
       The second formula for any compound, and the most crucial, is the molecular formula. This represents the actual number of atoms present in the molecule; thus for methane it is CH4, for ethane it is C2H6, and so on. 
       The final formula for any compound, and a highly important one, is the structural formula of the molecule of the compound. This formula shows all the atoms in the molecule and how they are bonded together. The structural formulae of the first eight alkanes are shown in the figure on the top.








    

Popular posts from this blog

WRITE A LETTER TO THE HEADTEACHER OF THE SCHOOL

Write a letter to a headteacher of the school in which you should : identify and evaluate the issues raised in the speech explain your views on whether the headteacher's proposal is the best way to benefit pupils at the school. Begin your letter with, 'Dear headteacher',... ANSWER :  Dear headteacher,         I accept your proposal that you have made such a big proposal towards children which seems to be very good for children and will keep the mind and body of children healthy and they will also be able to do their work and they will understand their responsibilities. And he will also learn to be free from mobile phones and video games and maintain his health, which will affect both their mind and their body in studies. And we expect from you that our children will enrol in sports in other studies too, they will be taken care of physically as well as mentally, and in school, morning circuit exercise is very good and before starting the school, An hour exercise ...
Read more

ALCOHOL AND HEALTH

Image
                                            Ethanol is the only alcohol that is safe to drink.it must only be drunk in moderation, if at all. Methanol is very toxic and in small amounts can cause blindness and death.        Ethanol mixes totally with water, which takes it everywhere in the body that water goes. The amount of alcohol that a person may drink varies with age, sex, weight and drinking history.       Heavy drinking can cause a healthy liver to become fatty and enlarged. Eventually scarring ( cirrhosis) can cause liver failure and death. Prolonged heavy drinking can eventually damage the muscle tissue of the heart. It may also lead to some long-term damage to brain. Alcohol is depressive drug and can be addictive. Drinking heavily on a particular occasion produces drunkenness, during which speech become slurred, vision is blurred and...
Read more

STEEL- MAKING

Image
                                                 The iron produced by the blast furnace is known as 'pig iron' or 'cast iron' and is not pure. It contains about 4% carbon, and other impurities. This amount of carbon makes the iron brittle. This limits the usefulness of the iron, though it can be cast (moulded) into large objects that are not likely to be subjected to deforming forces.        Most of the pig iron produced is taken to make steel. The carbon content is reduced by burning it off as carbon dioxide. Any sulphur contaminated is oxidised to sulphur dioxide. This basic oxygen process  is carried out in a tilting furnace. The method is fast: 350 tonnes of molten iron can be converted in 40 minutes. Scrap steel is added to the molten pig iron for recycling. A high-speed jet of oxygen is blown into the vessel through a water-cool...
Read more