Question

What is aldehyde? Write IUPAC name and formula of first three members of this series.

Answer 1

Organic compounds that contain the $-CHO$ group are included in the Aldehyde series. All members of the Aldehyde series have the general formula of ${{C}_{n}}{{H}_{2n}}O$ where $n$ represents the number of carbon atoms. To write the IUPAC name, we simply substitute the suffix ‘e’ by ‘al’ of relative alkane.

Complete Solution :
The common structure of an aldehyde can be represented as follows:
$R-\overset{\overset{O}{\mathop{||}}\,}{\mathop{C}}\,-H$
The double bond between carbon and oxygen is characteristics of all aldehydes and is known as the carbonyl group. Also, the carbon atom bonded to the hydrogen atom and $R$ group is any generic alkyl or side chain.

First three aldehydes include:
1. Formaldehyde ($HCHO$)
$H-\overset{\overset{O}{\mathop{\text{ }\\!\\!|\\!\\!\text{ }\\!\\!|\\!\\!\text{ }}}\,}{\mathop{C}}\,-H$
IUPAC name: Methanal

2. Acetaldehyde ($C{{H}_{3}}CHO$)
${{H}_{3}}C-\overset{\overset{O}{\mathop{\text{ }\\!\\!|\\!\\!\text{ }\\!\\!|\\!\\!\text{ }}}\,}{\mathop{C}}\,-H$
IUPAC name: Ethanal

3. Propanaldehyde ($C{{H}_{3}}C{{H}_{2}}CHO$)
${{H}_{3}}C-C{{H}_{2}}-\overset{\overset{O}{\mathop{\text{ }\\!\\!|\\!\\!\text{ }\\!\\!|\\!\\!\text{ }}}\,}{\mathop{C}}\,-H$
IUPAC name: Propanal

Note: Aldehydes are derived from alcohols by dehydration (removal of hydrogen).
Formaldehyde is a gas that forms formalin with 40% solution in water. Formalin is used for preserving biological specimens. Formaldehyde is used in the production of resins when combined with melamine, phenol and urea. It is also used in tanning, embalming and preparing germicide, insecticide and fungicide for plants.
- Acetic acids and pyridine derivatives are prepared from acetaldehyde.