Sum of number of oxygen atoms in S and T is .
Answer
2
Solution
P ( C9H18O2, DBE = 1): one C=C (decolorises Br2 water) + two –OH; iodoform +, so a CH3CH(OH)- unit. S and T come from PCC oxidation then heating (decarboxylation), so Q and R are β-hydroxy acids.
[figure] (P) [(ii) H2O2](i) O3 [figure] (Q) + [figure] (R)
Oxidative ozonolysis cuts the C=C and turns each =CH– into –COOH. Q has CH3CH(OH)- (iodoform +); R does not (iodoform –).
[figure] PCC [figure] [-CO2] [figure] (S)
PCC oxidises the 2° alcohol to a ketone; the β-keto acid loses CO₂ on heating. S = acetone (iodoform +).
[figure] PCC [figure] [-CO2] [figure] (T)
Same two steps; T = butan-2-one, a methyl ketone (iodoform +).
O atoms: S = 1, T = 1; sum = 2
Answer: 2