Question

Give the structural formulae of first four homologues of alkanes and alkenes.

Short answer

Answer: The structural formulae of the first four homologues of alkanes are: 1. Methane (CH4): H | C | H 2. Ethane (C2H6): H H | | C-C | | H H 3. Propane (C3H8): H H H | | | C-C-C | | | H H H 4. Butane (C4H10): H H H H | | | | C-C-C-C | | | | H H H H The structural formulae of the first four homologues of alkenes are: 1. Ethene (C2H4): H H | | C=C | | H H 2. Propene (C3H6): H H H | | | C=C-C | | | H H H 3. Butene (C4H8): H H H H | | | | C=C-C-C | | | | H H H H 4. Pentene (C5H10): H H H H H | | | | | C=C-C-C-C | | | | | H H H H H

Step-by-step solution

Understand Alkanes and Alkenes

Alkanes are hydrocarbons with single bonds between carbon atoms (C) and are saturated. Their general formula is CnH2n+2. Alkenes are hydrocarbons with one double bond between two carbon atoms and are unsaturated. Their general formula is CnH2n.

First Homologue of Alkanes

For the first homologue, n=1. Using the general formula for alkanes, CnH2n+2, we get the molecular formula C1H4, which is methane (CH4). The structural formula is: H | C | H

Second Homologue of Alkanes

For the second homologue, n=2. Using the general formula for alkanes, CnH2n+2, we get the molecular formula C2H6, which is ethane (C2H6). The structural formula is: H H | | C-C | | H H

Third Homologue of Alkanes

For the third homologue, n=3. Using the general formula for alkanes, CnH2n+2, we get the molecular formula C3H8, which is propane (C3H8). The structural formula is: H H H | | | C-C-C | | | H H H

Fourth Homologue of Alkanes

For the fourth homologue, n=4. Using the general formula for alkanes, CnH2n+2, we get the molecular formula C4H10, which is butane (C4H10). The structural formula is: H H H H | | | | C-C-C-C | | | | H H H H

First Homologue of Alkenes

For the first homologue, n=2. Using the general formula for alkenes, CnH2n, we get the molecular formula C2H4, which is ethene (C2H4). The structural formula is: H H | | C=C | | H H

Second Homologue of Alkenes

For the second homologue, n=3. Using the general formula for alkenes, CnH2n, we get the molecular formula C3H6, which is propene (C3H6). The structural formula is: H H H | | | C=C-C | | | H H H

Third Homologue of Alkenes

For the third homologue, n=4. Using the general formula for alkenes, CnH2n, we get the molecular formula C4H8, which is butene (C4H8). The structural formula is: H H H H | | | | C=C-C-C | | | | H H H H

Fourth Homologue of Alkenes

For the fourth homologue, n=5. Using the general formula for alkenes, CnH2n, we get the molecular formula C5H10, which is pentene (C5H10). The structural formula is: H H H H H | | | | | C=C-C-C-C | | | | | H H H H H