Backbone custom method - backbone.js

Question

I'm building a shopping cart with Backbone and I'm having a hard time determining how to structure the interaction with the server. When the user hits the checkout (and after the validation) I need to:
Save the Order using order.save() - Because the order was created on the client this will hit the route on the server and give me back an ID. I need the ID before I process the order.
On success I call a custom method on the Order which hits the server again which does a request to the card processing service.
I either report the err to the client and let him modify and retry or I update the order record and create a Payment record in the database.
Here is my processOrder method in the Order Model:
processOrder: function() {
var order = this.toJSON();
$.ajax({
url: '/api/order/process',
type: 'POST',
data: order,
dataType: 'json',
success: function(res) {
console.log(res);
},
error: function(err) {
//show error message
console.log('error: ' + JSON.stringify(err));
}
});
}
This is where the form is submitted in my view
saveOrder: function() {
...
var order = this.order;
order.set(this.frmJSON);
order.save(this.frmJSON, {
success: function(res) {
console.log('order saved...');
order.processOrder();
},
error: function(err) {
console.log(JSON.stringify(err));
}
});
}
The order is saved on the server and the Order gets an ID inserted into it. When I call processOrder it works until it gets to the ajax call. It never hits the server and the browser hangs up with no error. Is there a better way to structure these steps?