In the following reaction sequence, the major product P is formed. [figure] Glycerol reacts completely with excess P in the presence of an acid catalyst to form Q. Reaction of Q with excess NaOH followed by the treatment with CaCl2 yields Ca-soap R, quantitatively. Starting with one mole of Q, the amount of R produced in gram is . [Given, atomic weight: H = 1, C = 12, N = 14, O = 16, Na = 23, Cl = 35, Ca = 40]
Answer
909
Solution
i) Hg2+/H3O+: Markovnikov hydration of the terminal alkyne gives a methyl ketone; ii) Clemmensen reduction: C=O → CH2; iii) H3O+, Δ: ester hydrolysis.
H-C C-(CH2)15-CO2Et Hg2+, H3O+ CH3- O \|C-(CH2)15-CO2Et
Zn-Hg/HCl CH3-(CH2)16-CO2Et H3O+, CH3(CH2)16COOH (P, stearic acid, C17H35COOH)
Glycerol + 3P (acid catalyst) → Q = glyceryl tristearate, (C17H35COO)3C3H5.
Q + 3NaOH → 3 C17H35COONa + glycerol; 2C17H35COONa + CaCl2 (C17H35COO)2Ca (R) + 2NaCl
1 mol Q → 3 mol soap anion → 1.5 mol R.
Molar mass of R = 2 × 283 + 40 = 606 g mol-1 ( C17H35COO- = 18 × 12 + 35 + 32 = 283).
Mass of R = 1.5 × 606 = 909 g
Answer: 909