Question

General formula of aldehyde is:
a.) \[{{C}_{n}}{{H}_{2n}}{{O}_{2}}\]
b.) \[{{C}_{n}}{{H}_{2n}}O\]
c.) \[{{C}_{n}}{{H}_{2n+1}}O\]
d.) \[{{C}_{n}}{{H}_{2n+2}}O\]

Answer 1

Hint: To answer this question, we should note that an aldehyde is a compound containing a functional group with the structure –CHO. We should understand that a general formula is a type of empirical formula that represents the composition of any member of an entire class of compounds.

Complete step by step answer:
We know that the aldehyde group is –CHO. We should know that in aldehydes there is an \[s{{p}^{2}}\]-hybridized, planar carbon center that is connected by a double bond to oxygen and a single bond to hydrogen.
We will now know about the naming of aldehydes containing compounds. We should know that acyclic aliphatic aldehydes are named as derivatives of the longest carbon chain containing the aldehyde group.

Let’s take one by one different alkane and we will attach an aldehyde group to them. So, first we should take methane having the formula \[C{{H}_{4}}\], its aldehyde derivative is HCHO. Now, we take a second alkane that is ethane, \[{{C}_{2}}{{H}_{6}}\]. So, its aldehyde derivative will be \[C{{H}_{3}}CHO\]. Its IUPAC name is ethanol. Now, let’s take a third alkane that is propane \[{{C}_{3}}{{H}_{8}}\]. And its aldehyde derivative is propanal \[\] \[{{C}_{2}}{{H}_{7}}CHO\] which is propanal.
From the above discussion, we will now tell the general formula of aldehyde. We should know that the general formula of alkyl group is \[{{C}_{n}}{{H}_{2n+1}}\] and hence general formula for aldehyde will be \[{{C}_{n}}{{H}_{2n+2}}O\] \[{{C}_{n}}{{H}_{2n+1}}CHO\] provided n = 0, 1, 2, 3. From this discussion, we now know that the general formula is \[{{C}_{n}}{{H}_{2n}}O\]
So, the correct answer is “Option B”.

Note: Let us know about the general formula. We should know that a general formula is a type of empirical formula that represents the composition of any member of an entire class of compounds. We should know that every member of the class of hydrocarbons has a general formula and every chemical entity will follow the same. For example, when we take one compound that is composed of hydrogen and carbon, the number of hydrogen atoms always being two or more than twice the number of carbon atoms. It should be noted that n stands for “any number,” the general formula of alkane class is therefore \[{{\text{C}}_{\text{n}}}{{\text{H}}_{\text{2n }+\text{ 2}}}\].