2–Hexyne gives trans–2–Hexene on treatment with :

Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of :

The main product of the following reaction is

$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $${C_6}{H_5}C{H_2}CH\left( {OH} \right)CH{\left( {C{H_3}} \right)_2}\buildrel {conc.{H_2}S{O_4}} \over \longrightarrow \,?$$

The treatment of $$C{H_3}MgX\,\,$$ with $$C{H_3}C \equiv C - H$$ produces