Question

Give the structural formula for ethanal.

• A. ${\mathrm{CH}}_3\mathrm{CHO}$
• B. $\mathrm{HCHO}$
• C. ${\mathrm{CH}}_2\mathrm{CO}$
• D. ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{O}$

Answer 1

The correct option is A

${\mathrm{CH}}_3\mathrm{CHO}$

The explanation for the correct answer:

Option (A) ${\mathrm{CH}}_3\mathrm{CHO}$

• In ethanal, the prefix ‘eth’ shows the presence of 2 carbon atoms.
• The suffix ‘al’ shows the presence of the aldehyde group$\left(\mathrm{CHO}\right)$.
• So, therefore the chemical formula of ethanal is ${\mathrm{CH}}_3\mathrm{CHO}$.
• The structural formula of ethanal is;

• Hence, option A ${\mathrm{CH}}_3\mathrm{CHO}$ is correct.

The explanation for the incorrect answer:-

Option (B) $\mathrm{HCHO}$

• In $\mathrm{HCHO}$ there is one Carbon atom and an Aldehyde group$\left(\mathrm{CHO}\right)$ is present.
• Since it contains only one atom the suffix will be ‘meth’.
• It contains an Aldehyde group$\left(\mathrm{CHO}\right)$ so the prefix will be ‘al’.
• Therefore, the compound name is 'Methanal.
• Hence option B $\mathrm{HCHO}$ is incorrect.

Option (C) ${\mathrm{CH}}_2\mathrm{CO}$

• In ${\mathrm{CH}}_2\mathrm{CO}$, two Carbon atoms, two Hydrogen atoms, and one Oxygen atom are present.
• Since it contains two atoms the suffix will be ‘eth’.
• It contains a ketone group$\left(\mathrm{CO}\right)$, so the prefix will be ‘one’.
• Therefore, the compound name is Ethanone.
• Hence option C ${\mathrm{CH}}_2\mathrm{CO}$ is incorrect.

Option (D) ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{O}$

• In ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{O}$ , two Carbon atom and one Oxygen atom is present.
• Since it contains two atoms the suffix will be ‘eth’.
• It contains an Oxygen atom so the prefix will be ‘oxy’.
• Therefore, the name will be ‘Ethoxy' radical.
• Radical is the atom, molecule, or ion which has an unpaired valence electron.
• Hence option D ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{O}$ is incorrect.

Therefore, the structural formula for ethanal is ${\mathrm{CH}}_3\mathrm{CHO}$, option (A) is the correct answer.