CHAPTER11                                                                                                                                    Organic Chemistry

Q1       Define Organic chemistry.

Ans     Organic chemistry can be define as,

1;         the branch of chemistry in which we study organic compounds called organic    chemistry.

            The analysis of large number of organic compounds proved that all organic compounds             containing carbon necessarily. Therefore organic chemistry was defined as.

2;         the branch of chemistry in which we study carbon containing compounds except            oxides             of carbon, carbonate, Bicarbonate , metal carbides and cynides.

            Further investigation show that organic compounds made up of only carbon and            hydrogen are called hydrocarbons. All other organic compounds may be regarded to            have   been derived from them. Therefore organic chemistry is now defined as,

3:         the branch of chemistry in which we study hydrocarbon and their derivative.

           

Q2       what do you mean by vital force theory. By whom it was rejected?

Ans     It was thought that organic compounds cannot be prepared outside the body of living    organism. Because it need some supernatural force called vital force. This was called          vital force theory.

            According to this theory organic compounds cannot prepare in laboratory or industry.

Wohler,s work: in 1828 friedrich wohler , a German chemist synthesized an important organic             compound urea from inorganic substances ammonium cynate, while ammonium cyanate        is prepared from potassium cyanate and ammonium chloride.

            NH₄Cl _(s) + KCNO_(s) ----heat→ NH₄CNO_(s) + KCl_(s)

            NH₄CNO_(s) ------- heat--→ (NH₂)₂CO

            This was the end of vital force theory. It proved that no such vital force is required for the             synthesis of organic compounds.

Q3       what are the elements present in the organic compounds?

Ans     Carbon is the necessarily element of all organic compounds while almost all organic             compounds containing hydrogen also along with C.

            Moreover some of the organic compounds may also contain oxygen, Nitrogen, halogen,             sulphur and phosphorus.

            The compounds containing elements other than carbon and hydrogen are consider the             derivative of hydrocarbon.

Q4       Describe the characteristics of organic compounds.

            Ans:  organic compounds have mostly common features different from inorganic             compounds. Dome of them are,

            1: Nature of elements. All organic compounds containing carbon necessarily.

            2: Nature of bonds : organic compounds are mainly formed by covalent bonds.

            3:Intermolecular forces of attraction.: As most of the organic compounds are non-       polar. Therefore they are held together by weak vander waal,s forces.

            4; melting point and boiling point. Due to weak intermolecular forces organic    compounds are volatile and have low melting and boiling point.

            5: inflammability: Most of the organic compounds are inflammabale. They catch fire and             burn and change to CO₂ and H₂O.

            6: solubility: As most of the organic compounds are non-polar. Therefore they are in     soluble in water. And soluble in organic solvent like in acetone, ether and benzene.

            7: Electrical conductivity: As organic compounds are non-polar and not ionizable or    non-electrolyte.Therefore they are poor conductor of electricity in molten and solution            states.

            8: thermal stability: organic compounds are thermally unstable. They decompose into elements by strongly heating.

            9: Reactivity: Organic compounds have slow rate of chemical reaction than inorganic             compounds..

            10:Isomerism. Different organic compounds containing the same Molecular ormula.         Such    different compounds are called isomers and this phenomena i called isomerism.

Q5       What are the main sources of organic compounds?

            SOURCES OF ORGANIC COMPOUNDS

            The main sources of organic componds are

            A; Animals and plants, Protein, carbohydrates, fats, enzymes, oil, vitamins etc are         all organic compounds obtained from plants and animals.

            B; Coal.Coal is the remains of living organism. These materials are buried under the     surface of the earth. Under high pressure and temperature these material are             changed to coal. Coal is the rich source of organic compounds.when coal is heated in     the absence of air, one of the product is coal tar, which contain 215 aromatic        compounds.                                                                                                             

            Coal is of many types which is classified on the basis of amount of carbon. They are

            Peat  →Lignite  → sub bituminous coal → Bituminous coal → Anthracite

            Anthracite contains the largest percentage of carbon i.e. 95%. This is the hardest            form.  

            C; Natural gas,

            It is obtained by the decomposition of organic matter.

            It is mainly consisting of Methane (CH₄) i.e.85% and 15% ethane, propane and butane             are also present in small amount.

            Coal gas is the mixture of CH₄, CO and H₂.

            D; Petroleum.

            Mineral oil is called petroleum when it is in the refined form.

            It is formed by slow bio chemical and chemical decomposition of the remain of     organic             matter found b/w the sedimentary rocks

            The raw form of the petroleum is called rock oil or crude oil.

            It is the mixture of hydrocarbon. Majority of these are open chain and cyclic alkanes.

            It is dark brown in colour and unpleasant smell. It is used as fuel and also for different   synthetic materials like plastics, rubber and explosives.

Q6       What are the main uses of organic compounds?

Ans     Organic compounds are very important. They are widely used in our daily life,

            1; the major nutrients of our food is protein , carbohydrates and fats are organic   compounds

            2: the medicines we use, preservative, plastics and rubber are organic compounds.

            3: the cloth and shoes we wear are all organic.

            4: cosmetics, soap and detergents are all organic.

            5: the chemical we used in agriculture for increasing per acre yield are all organic.

            6; Tooth paste, tooth brush etc are organic in nature.

            In short organic chemistry is applied from our kitchen to agriculture , defense, our           physical hygiene and in all industries.  

Q7       Write note onAlkanes:

Ans:    Alkanes are saturated hydrocarbons in which all bonds are single covalent. The general formula of             which is CnH2n +2 while n is the number of carbon.

            The first four members are as under

            CH₄ ,               CH₃—CH_3­      CH₃—CH_2­—CH₃       CH₃—CH₂—CH₂—CH₃

            Methane          Ethane                             Propane                              Butane.

            Alkanes are also called paraffin. Which means less affinity. Because alkanes are chemically less    reactive.