Algorithms: does the simultaneous search for max / min in the set of x and y coordinates increase the comparisons?

I have an unclassified array of coordinates (x, y) and I need to find the minimum / maximum for both (x) and (y) separately in order to build a bounding box using $ O ( frac {3n} {2}) $ comparisons

If I order the matrix first by the x coordinates and then use this method to find the minimum / maximum for the limits of the left / wrestling box, then order the same matrix by the y coordinates and use the same algorithm to find minimum / maximum of y for the upper / lower limits, does this double the number of comparisons or can I claim that it is $ O ( frac {3n} {2}) $?