Yeah, so if you had  if I try and draw it much the same  if you had that  and let's choose  let's choose er, well le , let's keep the same  let's keep to the same carbon chain  if you had that  the carbon skeleton is exactly the same  the only way it differs is that the O H group here is on carbon one  of that chain that we've chosen  where as here, it's on carbon two of that chain.