In sulphur estimation by Carius method, the amount of BaSO4 formed from 3.79 g of M is g.
Answer
2.33
Solution
[figure] [anhyd. AlCl3]ClCOCH2Cl [figure]
Friedel–Crafts acylation at C-4 (ortho to one CH3, para to the other; both groups activate this position).
[figure] [heat]NaI [figure]
Finkelstein reaction: Cl is replaced by I.
[figure] sodium 3-nitrophenoxide [figure] (J)
Williamson synthesis: the phenoxide ion displaces I- (SN2).
[figure] NaBH4 [figure]
NaBH4 reduces the ketone to a 2° alcohol (the -NO2 group is not touched).
[figure] PBr3 [figure] (K)
OH is replaced by Br: K = C16H16BrNO3 =350 g mol-1 (matches the given value).
[figure] PhSNa [figure] (M)
SN2 by PhS-: M = C22H21NO3S, molar mass 350-80+109=379 g mol-1.
Moles of M = 3.79379=0.01; one S per molecule gives 0.01 mol BaSO4
Mass of BaSO4=0.01 233=2.33 g
Answer: 2.33