Final answer:
The Wittig synthesis is preferred over dehydrohalogenation as it allows for the preparation of alkenes with high stereoselectivity, crucial for the biological activity of pharmaceuticals like taxol.
Step-by-step explanation:
The advantage of a Wittig synthesis over dehydrohalogenation is highlighted by its use in the efficient synthesis of complex molecules like taxol, where the goal is to improve synthesis by reducing waste and enhancing the accessibility of life-saving drugs. The Wittig reaction allows the preparation of alkenes with high stereoselectivity, which is not possible with dehydrohalogenation and typically suffers from a lack of selective control in the formation of E/Z isomers. The Wittig reaction involves the creation of a ylide, which then reacts with an aldehyde or ketone to form an alkene directly, facilitating the formation of distinct geometric isomers. This stereoselectivity is crucial in pharmaceutical synthesis, where the biological activity of a molecule can be dependent on its stereochemistry.