Final answer:
The nucleophilicity of halide ions in acetic acid increases with decreasing electronegativity of the halogen, from fluoride to iodide, influenced by inductive effects and stability of the conjugate base.
Step-by-step explanation:
The relative nucleophilicity of halide ions can be understood in the context of their ability to donate an electron pair to an electrophile. In an acetic acid solution, the order of nucleophilicity typically follows the trend of halogen electronegativity in reverse, meaning that the less electronegative the halogen, the more nucleophilic the halide ion. Inductive effects and the stability of the resultant conjugate base also play significant roles in determining nucleophilicity.
In acetic acid, a strong acid like hydroiodic acid (HI) dissociates completely, indicating that the iodide ion is a good leaving group and, by extension, also a good nucleophile in this solvent. Consequently, one can infer that the nucleophilicity of halides in acetic acid increases from fluoride to iodide. Therefore, the expected order of increasing nucleophilicity of halide ions in acetic acid would be F- < Cl- < Br- < I-.