How to check the character is falling after jumping , 2D - C#

Hey everybody!
Im new to unity , I used this c# code to rotate the character(45 ) , if it goes up(when using space button ) and after that goes down and rotate (-45) , but it doesn’t work well ! do you know what should i change ? when it start to rotate , it doesn’t stop !
using UnityEngine;
using System.Collections;

public class Player : MonoBehaviour {

public Vector2 jumpForce = new Vector2(0,300);
bool isFalling;
bool playerFalling;
bool jumped;

void Update () {

	if (Input.GetKeyUp ("space")) {
					jumped = true;
					rigidbody2D.velocity = Vector2.zero;
				    rigidbody2D.AddForce (jumpForce);
	if (rigidbody2D.velocity.y > -0.1 && isFalling == false ) {

		                	transform.Rotate (0, Time.deltaTime * 45, 45, Space.World);     
				}
			}

	if (rigidbody2D.velocity.y < -0.1 && jumped) {
				isFalling = true;
				transform.Rotate (0, Time.deltaTime * (-45), (-45), Space.World);

			}