An organic compound P having molecular formula gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with gives compound S as the major product.
The total number of methyl () group(s) in compound S is _____.
Official answer: 6
P. that gives the ferric chloride test, has no intramolecular H-bond, and forms a trioxime with 3 equivalents of is phloroglucinol (benzene-1,3,5-triol). Its keto tautomer is cyclohexane-1,3,5-trione, which is what reacts as a triketone.
Q. The trioxime of that triketone.
R. Excess /KOH C-methylates each active twice, giving 2,2,4,4,6,6-hexamethylcyclohexane-1,3,5-trione: 6 methyl groups.
S. Excess iso-butylmagnesium bromide adds to each , giving three tertiary alcohols, each carrying a group (2 each):
Alternative. The three ketones are very hindered, so iso-butyl Grignard can instead act as a hydride donor (β-hydride transfer). That reduces them to the triol, which keeps only the 6 ring methyls. The official key accepts 6 or 12.