Question

An oxygen containing organic compound upon oxidation forms a carboxylic acid as the only organic product with its molecular mass higher by $14\text{ }units$. The organic compound is:
A.A ketone
B.An aldehyde
C.A primary alcohol
D.A secondary alcohol

Answer 1

The hydrocarbons which contain carbonyl groups undergo oxidation and they form carboxylic acid as a last step. In other words, all the organic compounds which have carbonyl groups could be converted into carboxylic acid by oxidation, in one or more than one step.

Complete step by step answer:
We will discuss structures of each compound given in the options, then we will thoroughly observe the values given in the question.
Option A has ketone, so generally it is a carbonyl group where oxygen is attached to a carbon through a double bond, and has two free valencies. It cannot be present at the terminal carbon of the hydrocarbon structure.
The next option is aldehyde, which is a $CHO$ group, where the oxygen is attached to the carbon with double bond and hydrogen is attached to the same carbon. It has just one valency and it could be terminal.
If we look at the third option, a primary alcohol, it is an –OH group attached to a terminal carbon. These types of alcohol are more easily oxidised as they are more reactive and have less steric hindrance than the secondary alcohol which is the next option. Secondary alcohol is when the hydroxide group is attached to a carbon which is also attached to two more carbons. Secondary alcohols on oxidation, results in formation of ketone.
Ketone needs drastic conditions to undergo the process of oxidation.
The primary alcohol has $C{{H}_{2}}OH$ this general chemical formula, so in order to convert it to carboxylic acid we need to remove two hydrogens and add one oxygen.
So the process can be expressed chemically as,
$-C{{H}_{2}}OH+{{O}_{2}}\to COOH$
In the overall process the molecular mass increases by $14\text{ }units$ as per the given question.
The atomic mass of hydrogen is $1g/mol$ and atomic mass of oxygen is$16g/mol$.
So, if we calculate the number of units which is added, we have to subtract the unit of hydrogen from oxygen as two hydrogens were removed and one oxygen was added in the process.
So we get $16-2\left( 1 \right)=~14$
So the correct option is C.

Note:
The oxidation of aldehyde also leads to formation of carboxylic acid but in that mass increases by 16 units.
Generally the oxidation of alcohol leads to aldehyde which in turn when oxidised, is converted to carboxylic acids.