Various methods exist to introduce this functionality. Carboxylic acids can be converted to trifluoromethyl groups by treatment with sulfur tetrafluoride and trihalomethyl compounds, particularly trifluoromethyl ethers and trifluoromethyl aromatics, are converted into trifluoromethyl compounds by treatment with antimony trifluoride/antimony pentachloride (the Swarts reaction). Another route to trifluoromethyl aromatics is the reaction of aryl iodides with trifluoromethyl copper. Finally, trifluoromethyl carbonyls can be prepared by reaction of aldehydes and esters with Ruppert's reagent.