First HBr was added to remove the double bond and add a bromine. Ether was then added so Br will attach to Mg. H3CH=O was then added so a oxygen will form. Then H3O+ was added so an H will be placed on the Oxygen. H2SO4 was then added so the hydroxyl would leave and cause a double bond to be formed. BR NBS cause two br to be put. Ether was added again so that Mg will attach to the two Br. 2H3 CH=O was added so two oxygen will be added. H3O+ was then added to put H on the two oxygen. H2SO4 was then added to remove the two OH and replace it wil double bonds. follow this link if you have confusion: (there is an explanation with diagrams) http://goo.gl/tK9gi Solution First HBr was added to remove the double bond and add a bromine. Ether was then added so Br will attach to Mg. H3CH=O was then added so a oxygen will form. Then H3O+ was added so an H will be placed on the Oxygen. H2SO4 was then added so the hydroxyl would leave and cause a double bond to be formed. BR NBS cause two br to be put. Ether was added again so that Mg will attach to the two Br. 2H3 CH=O was added so two oxygen will be added. H3O+ was then added to put H on the two oxygen. H2SO4 was then added to remove the two OH and replace it wil double bonds. follow this link if you have confusion: (there is an explanation with diagrams) http://goo.gl/tK9gi.