Sec 1 Preparation of RX ■3.From alcohol ROH PCls- →RCl+POCL3+HCI (phosphorus oxychloride) ROH+PCL3→RCI+HPO3 ROH+P+Br2→RBr+H3PO3 We rarely start with PCla,PBra or PI3,since they are easily hydrolysed by moisture in air. Instead,they are made in situ,using red phosphorus in the alcohol and halogen is put into the reaction flask as the reaction proceeds