scheme help pls

hey /prog/, I'm trying to do something simple and failing hard. I seem to be missing something obvious, but I'm not sure what. Using DrScheme here.

Suppose I have a list that represents infix notation, e.g.,
(1 + 2)
and I want to evaluate it. I can create a list that is in prefix notation assuming a simple list in this form:
(define infix->prefix (lambda (x)
                          (list (cadr x)
                                         (car x)
                                         (caddr x))))
And then
> (infix->prefix '(2 + 3))
(list '+ 2 3)
>
But, er, how would I evaluate this? That is, what am I missing so that
> (infix->prefix '(2 + 3))
5
>

Thanks for any insight.

Fuck Scheme and fuck precedence too.

(defun i->p (x)
   (cond ((atom x) x)
         ((cdr  x) (let ((y (reverse x)))
                      (list (cadr y) (i->p (reverse (cddr y))) (i->p (car y)))))
         (t        (car x))))

(defmacro infix x (i->p x))