The compounds which are missing 4 or more hydrogen atoms are called alkynes and are characterized by the presence of triple carbon-carbon bonds. They have a general formula C_nH_2n-2, indicating two fewer hydrogen atoms than alkenes, which have double bonds, and four fewer than alkanes, which only have single bonds.

Some common examples of alkynes are:

1. Acetylene (C₂H₂): It's the simplest alkyne and forms the building block for many other organic compounds.

2. Propyne (C₃H₄): This three-carbon alkyne is used as a fuel in some gas mixtures.

3. Butyne (C₄H₆): A four-carbon alkyne that finds application in organic synthesis.

4. Phenylacetylene (C₈H₈): A more complex alkyne that's used as an intermediate in the production of various pharmaceuticals and fragrances.

These compounds exhibit unique properties due to their highly unsaturated nature, including relatively high reactivity, low boiling points, and the ability to undergo various addition reactions. Alkynes play a crucial role in diverse chemical industries and are essential starting materials for the synthesis of numerous other chemicals, pharmaceuticals, and materials.