In the replacement reaction
`rarrC-I+MF rarr rarr C-F+MI`
The reaction will be most favourable if `M` happens to be

Options

A. Na
B. K
C. Rb
D. Li.

Answer

C

Explanation

`3^(@)` Alkyl halides undergo `S_(N^(1))` reaction in which a nucleophiles attacks a carbocation. Thus more the ionic character of the M-F bond, more favourable will be the replacement reaction. Since amongest Li, Na, K and Rb, Rb has the largest size, therefore Rb-F bond has the highest ionic character and therefore, option (C ) is correct.