# Is the conversion of sodium perrhenate to the tetrabutylammonium salt a double replacement reaction?

Mar 17, 2015

Yes, the conversion of sodium perrhenate to a tetrabutylammonium salt is a double replacement reaction; this reaction is actually a salt metathesis reaction, which is an alternative name given to a reaction in which counterions (cations and anions) exchange partners.

The general form for a metathesis reaction looks like this

$\text{AX" + "BY" -> "AY" + "BX}$, where

$A$, $B$ - cations;
$X$, $Y$ - anions.

In your case, the reaction between sodium perrhenate, or $N a R e {O}_{4}$, and tetrabutylammonium chloride, or ${\left(C {H}_{3} {\left(C {H}_{2}\right)}_{3}\right)}_{4} N C l$ (you'll sometimes see this written as $N {\left({C}_{4} {H}_{9}\right)}_{4} C l$), will produce sodium chloride, or $N a C l$, and tetrabutylammonium perrhenate, or $N {\left({C}_{4} {H}_{9}\right)}_{4} R e {O}_{4}$.

$N a R e {O}_{4} + N {\left({C}_{4} {H}_{9}\right)}_{4} C l \to N a C l + N {\left({C}_{4} {H}_{9}\right)}_{4} R e {O}_{4}$

The reaction takes place in aqueous solution (aq), and the tetrabutylammonium perrhenate salt will precipitate from solution.

The counterions that will exchange partners are $N {a}^{+}$ and $N {\left({C}_{4} {H}_{9}\right)}_{4}^{+}$ (cations), and $R e {O}_{4}^{-}$ and $C {l}^{-}$ (anions).