The general form for the period of a sine function \( f(x) = \sin(kx) \) is given by:
\[
{Period} = \frac{2\pi}{|k|}
\]
For the function \( f(x) = \sin\left( \frac{3x}{2} \right) \), the coefficient \( k = \frac{3}{2} \).
Substituting \( k \) into the period formula:
\[
{Period} = \frac{2\pi}{\left|\frac{3}{2}\right|} = \frac{2\pi}{\frac{3}{2}} = \frac{4\pi}{3}
\]
Thus, the period of the function is \( \frac{4\pi}{3} \).