In this method the sample alcohol is treated with PI3 to get the iodoalkane which is again treated with AgNO2 to get the nitroalkane. The nitroalkane is then treated with nitrous acid which is obtained by NaNO2 and HCl.
This method involves a sequence of chemical transformations starting with alcohol treatment with PI3 followed by conversion to an iodoalkane, then AgNO2 for nitroalkane formation, and finally, the use of nitrous acid prepared from NaNO2 and HCl.