Question

Which of the following is the first member of ester homologous series?
A.Ethyl ethanoate
B.Methyl ethanoate
C.Methyl methanoate
D.Ethyl methanoate

Answer 1

Hint: We have to know that the ester is a chemical compound which is prepared from acid by the placing of hydrogen by another organic group or other alkyl group. The essential oils and naturally occurring fats are the examples of esters. And the formation of esters is an example of substitution reaction. We must have to know that the ester is mainly used for the preparation of perfumes, cosmetics etc.

Complete answer:
We also remember that the ester homologous series are not started with ethyl ethanoate. Its formula is$$C{H}_3-CO-O-C{H}_2-C{H}_3$$. Hence, option (A) is incorrect.
We must have to know that the methyl ethanoate is not the first member of ester homologous series. $$C{H}_3-CO-O-C{H}_3$$ is the formula of methyl methanoate. Hence, the option (B) is incorrect.
Among the given options, methyl methanoate is the first member of ester homologous series. And the formula of methyl methanoate is, $$H-CO-O-C{H}_3$$ and it is prepared from formic acid and methanol. The chemical reaction can be written as,
$$HCOOH+C{H}_{3}OH\to H-CO-O-C{H}_3+H_{2}O$$
Hence, option (C) is correct.
We must have to remember that the ethyl methanoate is the second member of ester homologous series. And its formula is $$H-CO-O-C{H}_2-C{H}_3$$. Hence, the option (D) is incorrect.

Note:
Among the given compounds, methyl methanoate is the first member of ester homologous series. And it is papered by the reaction of formic acid with methanol by condensation reaction. We have to remember that methyl methanoate is also known as methyl formate. And each successive group can be acquired by the addition of the methylene group into the homologous series.