Prepare an alkyne from each alkene precursor by the dehydrohalogenation of alky1 dihalides method.

First, identify the given alkene precursor and its structure, as well as the desired alkyne product. The structure must be drawn to understand the molecular changes that will occur.

Convert the alkene precursor to a geminal or vicinal dihalide by adding halogen across the double bond. This is achieved through a halogenation reaction in which the alkene reacts with a molecular halogen (such as Cl2 or Br2). The halogen will add across the double bond and form a dihalogenated product.

Carry out the dehydrohalogenation reaction to form the alkyne from the dihalide. In this reaction, a strong base (such as sodium amide, NaNH2, or potassium tert-butoxide, t-BuOK) is required to remove two hydrogen-halogen (HX) bonds. This can be done in one or two steps, depending on whether the dihalide is a geminal or vicinal dihalide. For a geminal dihalide, two successive dehydrohalogenation reactions are needed to remove both hydrogen-halogen bonds and form the alkyne: 1. The base attacks the hydrogen atom bonded to the carbon adjacent to the halogen, and the electrons in the hydrogen-halogen bond will move to form a double bond, thereby releasing the halide ion. This step forms a new alkene. 2. The process is repeated, with the base attacking the new alkene, removing the second hydrogen-halogen bond, and forming a triple bond to create the alkyne product. For a vicinal dihalide, only one dehydrohalogenation reaction is required. The base attacks one of the hydrogen atoms bonded to adjacent carbons and the electrons in the hydrogen-halogen bond form a triple bond, releasing two halide ions in a single step.

Review the final product to ensure that it matches the desired alkyne structure from Step 1.