Help Rotating a Player

I'm making a 2.5D platformer and have my movement system done and it works fine. Now, I need to work on some simple animation. The first thing I'm tackling is getting the player to look to either the right or the left. depending on which way it's going. I also want it to be a rotation instead of an instant change. This is what I have so far, but it doesn't seem to work. using UnityEngine; using System.Collections;

 public class playeranimator : MonoBehaviour {
     public float rotSpeed;
     public GameObject player;
     public Quaternion leftRot;
     public Quaternion rightRot;
     public Quaternion playerRot;
     // Use this for initialization
     void Start ()
     {
         rotSpeed = 10f;
         leftRot.eulerAngles = new Vector3(0, 90, 0);
         rightRot.eulerAngles = new Vector3(0, 180, 0);
     }
     // Update is called once per frame
     void Update ()
     {
 
     }
     //rotates the player
     void Rotate ()
     {
         playerRot.eulerAngles = new Vector3(player.transform.eulerAngles.x, player.transform.eulerAngles.y, player.transform.eulerAngles.z);
         if (Input.GetKeyDown(KeyCode.D))
         {
             transform.rotation = Quaternion.Lerp(playerRot, rightRot, Time.time * rotSpeed);
         }
     }
 }

rightRot, leftRot, and playerRot don't seem to actually do anything. playerRot doesn't actually update to the rotation of the player, and the player doesn't rotate at all when it is supposed to. Any help on this would be great, or if there's a better way to do it, let me know. Any tips of formatting code is also helpful, as I didn't get any proper training.