Carbon and its Compounds PDF

unit? Do you see any relation between the number of carbon and hydrogen atoms in these compounds? The general formula for alkenes can be written as CnH2n, where n = 2, 3, 4. Can you similarly generate the general formula for alkanes and alkynes? As the molecular mass increases in any homologous...

unit? Do you see any relation between the number of carbon and hydrogen atoms in these compounds? The general formula for alkenes can be written as CnH2n, where n = 2, 3, 4. Can you similarly generate the general formula for alkanes and alkynes? As the molecular mass increases in any homologous series, a gradation in physical properties is seen. This is because the melting and boiling points increase with increasing molecular mass. Other physical properties such as solubility in a particular solvent also show a similar gradation. But the chemical properties, which are determined solely by the functional group, remain similar in a homologous series. Activity 4.2 n Calculate the difference in the formulae and molecular masses for (a) CH3OH and C2H5OH (b) C2H5OH and C3H7OH, and (c) C3H7OH and C4H9OH. n Is there any similarity in these three? n Arrange these alcohols in the order of increasing carbon atoms to get a family. Can we call this family a homologous series? n Generate the homologous series for compounds containing up to four carbons for the other functional groups given in Table 4.3. 4.2.5 Nomenclature of Carbon Compounds 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. For example, the names of the alcohols taken in Activity 4.2 are methanol, ethanol, propanol and butanol. Naming a carbon compound can be done by the following method – (i) Identify the number of carbon atoms in the compound. A compound having three carbon atoms would have the name propane. (ii) In case a functional group is present, it is indicated in the name of the compound with either a prefix or a suffix (as given in Table 4.4). (iii) If the name of the functional group is to be given as a suffix, and the suffix of the functional group begins with a vowel a, e, i, o, u, then the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix. For example, a three-carbon chain with a ketone group would be named in the following manner – Propane – ‘e’ = propan + ‘one’ = propanone. (iv) If the carbon chain is unsaturated, then the final ‘ane’ in the name of the carbon chain is substituted by ‘ene’ or ‘yne’ as given in Table 4.4. For example, a three-carbon chain with a double bond would be called propene and if it has a triple bond, it would be called propyne. Carbon and its Compounds 67 2024-25