Question

What are homologous series of carbon compounds? Write the molecular formula of two consecutive members of a homologous series of aldehydes. State which part of these compounds determines their physical and chemical properties.

Answer 1

Basically, homologous series are series of compounds with similar chemical properties and some functional group differing from the successive members of $C{H_2}$ . Moreover, these members of the homologous series can be represented by a general formula.

Complete step by step answer:
Now, we have three parts in the question. In the first part we will discuss the homologous series of carbon compounds. Basically, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched. Moreover, carbon chains of varying length have been observed in organic compounds having the same general formula. Alkanes with general formula ${C_n}{H_{2n + 2}}$ , alkenes with ${C_n}{H_{2n}}$ and alkynes with ${C_n}{H_{2n - 2}}$ form the most basic homologous series in organic chemistry.
Now, two consecutive members of homologous series of aldehydes are $C{H_3}CHO$ and ${C_2}{H_5}CHO$ Moreover, a carbon compound is made up of two parts i.e. $R - F$ , where R refers to the hydrocarbon part and F is the functional group part. So, the R part i.e. the hydrocarbon part determines the physical properties of a compound whereas the F part i.e. the functional group part determines the chemical properties of the respective compounds. The physical properties such as melting point, boiling point, density, gradually increase with the increase in the molecular weight whereas the chemical properties closely resemble due to the presence of the same functional group. Therefore, we have discussed all the three parts given in the question.

Note:
This series has enabled the scientists and engineers to study different organic compounds systematically. Moreover, they can predict the properties of organic compounds belonging to a particular homologous series based on the data that is available from the other members of the same series. Overall, the study of organic compounds has been simplified.