Hydrocarbon derivatives are formed when one or more hydrogen atoms is replaced by an element or a group of elements other than hydrogen. General purpose of this lecture is to briefly present on Hydrocarbon Derivatives. Here also Alcohol and Halogens. An alcohol has a hydrogen replaced by a hydroxyl (-OH) group. Halogens (F2, Cl2, Br2, I2,) can all add to a hydrocarbon to form am alkyl halide. The name of the hydrocarbon that was substituted determines the name of the alcohol.