Animated Solution for Chemistry - Organic Chemistry: A solution of phenol in chloroform when treated with aqueous NaOH gives compound P as a major product. The mass percentage of carbon in P is ……… . (to the nearest integer) (Atomic mass: $C=12;H=1;O=16$)

Imagine you are in a chemistry lab, holding a flask of phenol. You add a splash of chloroform and some aqueous sodium hydroxide. What happens next is not just a random mixing of chemicals; it's a beautifully choreographed dance of molecules known as the Reimer-Tiemann reaction.

This classic named reaction is a favorite among examiners because it tests your memory of organic reagents and your understanding of electrophilic aromatic substitution.

When phenol reacts with $CHC{l}_3$ and $NaOH$, the base first deprotonates the phenol to form a phenoxide ion, which is highly reactive. Simultaneously, the base reacts with chloroform to generate a highly reactive, electron-deficient species called dichlorocarbene ($:CC{l}_2$).

This carbene attacks the electron-rich ortho position of the phenoxide ring. After a series of proton transfers and hydrolysis steps, an aldehyde group ($-CHO$) is firmly attached to the ring.

The major product formed is ortho-hydroxybenzaldehyde, commonly known as salicylaldehyde. This is our "Compound P".

Now that we have identified Compound P, the chemistry part is over, and the math begins! We need to find the mass percentage of carbon in salicylaldehyde.

First, let's determine its exact molecular formula. The structure consists of a benzene ring (which has 6 carbons), an $-OH$ group, and a $-CHO$ group.

Counting the atoms carefully: - Carbon: 6 from the ring + 1 from the aldehyde = 7 carbons. - Hydrogen: 4 from the ring (since two positions are substituted) + 1 from the hydroxyl + 1 from the aldehyde = 6 hydrogens. - Oxygen: 1 from the hydroxyl + 1 from the aldehyde = 2 oxygens.

This gives us the molecular formula: $C_7{H}_6{O}_2$.

To find the mass percentage, we first need the total molar mass of the compound. We use the given atomic masses: $C=12$, $H=1$, and $O=16$.

The total mass contributed by carbon alone is $84\text{ g/mol}$. The mass percentage of carbon is simply the mass of carbon divided by the total mass, multiplied by 100.

The question specifically asks us to round to the nearest integer. Since the decimal part is $.85$, which is greater than $.5$, we round up.

This problem is a fantastic reminder of how organic chemistry and physical chemistry often intertwine. Always read the reagents carefully, and never rush the final arithmetic!