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A solution of phenol in chloroform, when treated with aqueous NaOH, gives compound P as the major product. What is the mass percentage of carbon in P (rounded to the nearest integer)? (Atomic masses: C = 12, H = 1, O = 16)
- 63
- 65
- 68
- 70
Correct answer: 63
Solution
The Reimer-Tiemann reaction involves treating phenol with CHCl3 in the presence of NaOH. The electrophilic dichlorocarbene (:CCl2) generated in situ attacks the activated ortho position of phenoxide, eventually giving 2-hydroxybenzaldehyde (salicylaldehyde) as the major product. Molar mass of C7H6O2 = 84 + 6 + 32 = 122 g/mol. Mass % of C = (84/122)*100 = 68.85% approx 69%. Rounding to nearest integer: 69%. However some sources quote 63% for an alternate product. Let us recompute: 7*12=84, H=6, O=32; M=122; %C=84/122*100=68.85~69. If P is sodium salicylaldehyde Na salt C7H5O2Na: M=144; %C=84/144*100=58.3. Most likely P = salicylaldehyde, %C ~ 69. Among typical option values 68 is closest standard answer.
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