Question

1. Offer a mechanistic interpretation of each of the following phenomena: Acetolysis of 1 is a stereospecific reaction and gives only 2. a. OMe OMe ACOH "Br "OAc b. Acetolysis of the following optically active bicyclic substrate,3, gives the indicated inactive acetate,4. AcОН TsO AcO 4 1-Aryl-2-propyl tosylates can solvolyze by either solvent assisted (k.) or aryl assisted (ka) pathways: c. inversion ks OTs ArCH,CHCH3 retention Since there are two competing mechanisms the Hammett plot for this reaction is nonlinear. Electron donating substituents on the ring lead to a much faster reaction than expected. The molecule meso-1,4-diaryl-2,3-butyl ditosylate: OTs ArCH,CHCHCH,Ar OTs can also solvolyze by two pathways. The nonlinearity of the Hammett plot for the ditosylate is much greater than that for the monotosylate. Explain these observations.

Answer 1

@ Acelolysis - BAC ACOM some POAC Here oxygen lone pair participate reaction. This effect is called group participation. during the neighbouring OTS GAC Acon Acon This reaction mechanism also involve Neighbouring group participation

OTS Arch-dych Ks Char Ch Ara OAC Acon Tson cң н" cho OAC Inversion. KA Acon OAC Aco... Refention Il electon donating group is present in benzene ring then rate of reaction is much faster because heighbouring group panicipation is active I Hamette plot shows nonlinearity for the ditosy late is much greater than for the mono- tosylate.