The key difference between Finkelstein and Swarts reaction is that the end product of Finkelstein reaction is alkyl iodide whereas the end product of Swarts reaction is alkyl fluoride.
Finkelstein reaction and Swarts reaction are important in the preparation of alkyl halides. Therefore, these are very important reactions in organic synthesis processes. Both these reactions involve the exchange of halides according to their reactivity.
CONTENTS
1. Overview and Key Difference
2. What is Finkelstein Reaction
3. What is Swarts Reaction
4. Side by Side Comparison – Finkelstein vs Swarts Reaction in Tabular Form
5. Summary
What is Finkelstein Reaction?
Finkelstein reaction is a type of organic reaction named after the scientist Hans Finkelstein. In this reaction, alkyl iodides are formed from other alkyl halides. It is a type of substitution reaction. We call it an SN2 reaction or a bimolecular reaction. Usually, these are equilibrium reactions. However, we can drive the reaction towards the completion using an excess amount of halide salt. Furthermore, this reaction works best with primary halides. Moreover, we can observe an exceptionally high yield using allyl and benzyl halides. However, the reaction with secondary halides is low. Also, vinyl, aryl and tertiary halides are unreactive.
Concerning the usefulness, this reaction is useful for the conversion of an alkyl chloride or an alkyl bromide into an alkyl iodide. This process includes the treatment of a solution of sodium iodide in acetone. It is because sodium iodide dissolves in acetone while sodium chloride and sodium bromide do not dissolve in acetone. The poorly soluble sodium chloride and sodium bromide tend to precipitate; thus, we can obtain sodium iodide as the final product due to mass action.
What is Swarts Reaction?
Swarts reaction is a type of organic reaction named after the scientist F. Swarts, who discovered it in the late 19th century. In this reaction, the exchange of halides with fluoride occurs to form alkyl fluorides. Most often, this reaction occurs with the substitution of chlorine with fluorine. Also, this reaction is carried out in the presence of antimony fluoride (SbF3). It is because the action of antimony is required for the reaction progression; it is a fluorinating agent. In addition to that, we can use some other metal fluorides such as silver fluoride (AgF) and mercury fluoride (Hg2F2), as well.
Figure 02: Antimony Trifluoride
In the industrial scale productions, the Swarts reaction is very important in the preparation of Freons. A variant for this reaction is the use of hydrogen fluoride (HF) along with salts of antimony (Sb) having +3 or +5 oxidation states. And, this variant is called fluorination.
What is the Difference Between Finkelstein and Swarts Reaction?
Both Finkelstein reaction and Swarts reaction are associated with alkyl halide productions. These reactions describe the exchange of halides between organic compounds (or organic and inorganic compounds) to prepare new alkyl halides. The key difference between Finkelstein and Swarts reaction is that the end product of Finkelstein reaction is alkyl iodide whereas the end product of Swarts reaction is alkyl fluoride. The reactant for Finkelstein reaction can be primary halides, secondary halides, allyl halides and benzyl halides, but this reaction is not applicable for tertiary reactions, vinyl and aryl halides. The reactants for Swarts reaction are either alkyl chloride or alkyl bromide along with a fluorinating agent such as antimony fluoride.
Below infographic tabulates the differences between Finkelstein and Swarts reaction.
Summary – Finkelstein vs Swarts Reaction
Finkelstein and Swarts reactions are associated with alkyl halide productions. These reactions describe the exchange of halides between organic compounds (or organic and inorganic compounds) to prepare new alkyl halides. The key difference between Finkelstein and Swarts reaction is that the end product of Finkelstein reaction is alkyl iodide whereas the end product of Swarts reaction is alkyl fluoride.
Reference:
1. “Finkelstein Reaction: Organic Chemistry Reactions.” BYJUS, Byju’s, 19 Jan. 2017, Available here.
Image Courtesy:
1. “Chrysochlamic-Acid-Finkelstein” By Rifleman 82 (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Antimony trifluoride” (Public Domain) via Commons Wikimedia