The 24-year-old was always going to be up against it in a high quality field.
The former Chorley Marlin smashed the British record on Wednesday but that was only good enough to see her finish third in her heat.
In all fairness the two swimmers to finish ahead of her in the heats went on to claim gold and silver.
Australia' s Emma McKeon was the winner, clocking a new Olympic record time of 51.96 to finish ahead of Hong Kong's Siobhan Haughey in second who was timed at 52.27.
The bronze medal went to Cate Campbell, also of Australia, in a time of 52.52.
Hopkin was not too far away from a medal in terms of her time as she came home in 52.83.
The GB swimmer was due to be in the pool again later on Friday for the 50m freestyle heats but did not take her place on the start line.
Support us and become a subscriber today. Enjoy unlimited access to local news, the latest football stories and new puzzles every day. With a digital subscription, you can see fewer ads, enjoy faster load times, and get access to exclusive newsletters and content. Click here to subscribe.