Carbon and its Compounds

Carbon and its compounds: An Introduction Carbon is a versatile element that forms the basis for all living organisms and many important things of our use. The symbol of Carbon is C and its atomic number is 6. Organic compounds are the compounds of carbon containing usually hydrogen and one or more additional elements such as oxygen, nitrogen, sulphur, halogens and phosphorous. Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. Catenation, tetracovalency of carbon and formation of multiple bonds are some unique properties of carbon. Carbon forms covalent bonds with itself and other elements such as hydrogen, oxygen, sulphur, nitrogen and chlorine. Carbon also forms compounds containing double and triple bonds between carbon atoms. These carbon chains may be in the form of straight chains, branched chains or rings. Hydrocarbons are the compounds of carbon and hydrogen. They are classified as saturated hydrocarbons (Alkanes) unsaturated hydrocarbons (Alkenes & Alkynes). Carbon exists in many allotropic forms which differ in arrangement of atoms. They have different physical properties and identical chemical properties. Diamond, Graphite, Fullerenes are some allotropic forms of carbon. Molecular models are the physical means to have better visualization and perception of 3D shapes of organic compounds.

Carbon and its compounds Ethanoic acid Ethanol and ethanoic acid are carbon compounds of importance in our daily live. The organic compounds containing carboxylic group (–COOH group) are called carboxylic acid. Ethanoic acid is the second member of the homologous series of carboxylic acids. The molecular formula of ethanoic acid is CH3COOH. Ethanoic acid is commonly known as acetic acid. Ethanoic acid is a colorless liquid with characteristic pungent vinegar odour and sour taste. 5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles. Ethanoic acid is acidic in nature. Chemical properties of ethanoic acid include reaction with carbonates and hydrogencarbonates, reaction with bases. When a mixture of ethanol, ethanoic acid and concentrated sulphuric acid is gently heated, ethyl ethanoate is formed. Ethanoic acid is used in making esters, which are used in perfumes.

Carbon and its compounds Ethanol Many carbon compounds are invaluable to us. Compounds containing alcoholic group (–OH) are called Alcohols. Ethanol is the second member of the homologous series of alcohols. Its molecular formula is C2H5OH. Ethanol is commonly called alcohol and is the active ingredient of all alcoholic drinks. Since it is a good solvent, it is also used in medicines such as tincture iodine, cough syrups and many tonics. Ethanol is miscible with water in all proportions. Consumption of small quantities of dilute ethanol causes drunkenness. Long-term consumption of alcohol leads to many health problems. To prevent the misuse of ethanol produced for industrial use, it is made unfit for drinking by adding poisonous substances like methanol to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol. Chemical properties of ethanol include reaction with sodium metal, dehydration, combustion reaction, oxidation reaction, reaction with carboxylic acid etc.

Homologous series and functional group Out of all the known elements carbon seems to be a very friendly element. Carbon forms bonds with other elements such as halogens, oxygen, nitrogen and sulphur, which are referred as heteroatom. These heteroatoms and the group containing these confer specific properties to the compound, regardless of the length and nature of the carbon chain and hence are called functional groups. Some important functional groups are alcohol, aldehyde, ketone etc. The names of compounds in a homologous series are based on the name of the basic carbon chain modified by a “prefix” “phrase before” or “suffix” “phrase after” indicating the nature of the functional group. Homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by a CH2 group. All the members of a homologous series can be represented by the same general formula. Each member of homologous series is called homologue. Combustion is the process of burning of a carbon compound in air to give carbon dioxide, water and light. Saturated hydrocarbons will generally give a clean flame while unsaturated carbon compounds will give a yellow flame with lots of black smoke. The reaction in which an unsaturated hydrocarbon combines with another substance to give a single product is called an addition reaction. Hydrogenation of vegetable oils is an example of addition reaction. Some other chemical properties of carbon compounds are substitution reactions, oxidation reaction etc.

Nomenclature and Isomerism Nomenclature implies assigning proper name to a particular compound on the basis of certain standard rules to make their study systematic. In the beginning, the organic compounds were named after source from which they were extracted or obtained. These names were called the trivial or common names. The drawbacks of the trivial system have been overcome by system given by IUPAC. IUPAC system adopts certain uniform rules to write the names of the organic compounds in a systematic manner. The names based upon these rules are called the IUPAC names. The name of an organic compound consists of three parts i.e., prefix, root word and suffix as per the IUPAC conventions. Organic compounds, having the same molecular formula but different structures are known as isomers. The phenomenon of existence of two (or more) different organic compounds having the same molecular formula but different structures is called isomerism. Isomerism can be broadly classified into structural and stereoisomerism. Compounds with identical molecular formula but different structures are called structural isomers.

Soaps and Detergents To maintain our personal hygiene we need to clean our body and clothes. For this some cleansing agents like soaps and detergents are used. Soaps are sodium or potassium salts of higher fatty acids. Soaps are prepared by heating animal fat or vegetable oil with sodium hydroxide or potassium hydroxide. Soaps can’t be used with hard water because they produce scum on the reaction of calcium and magnesium salts present in hard water. This problem is overcome by using detergents as cleansing agents. Detergents are sodium salts of long chain sulphates and sulphonates. They can be used in hard water also. Molecules of soaps and detergents have hydrophobic as well as hydrophilic parts. The cleansing action of soaps and detergents proceeds by the formation of micelles which helps in emulsification and removal of the oil and dirt.

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