Is oil bath better for this reaction

gomer · Thu Sep 29, 2005 8:16 am

ok swim currently uses an electric stove top to react pyridine hcl with codeine but it is very difficult to get it exactly right for best yield.The heat is difficult to get correct and although it works ok it is often over cooked or under cooked and only sometimes exactly right,swims freind when he was in NZ showed swim this procedure and cause he had alot of experience with it this guy always got spot on,but as swim has only done this a handful of times he is not as luckyand only seldom gets it spot on as it is hard to tell when the viscosity changes and the reaction is perfectly ready.Could some1 with more experience please tell swim if an oil bath would be a more reliable way to do this and if so what temp should the oilbath be set at and how long should swim put the buisness end of the reaction tube in the oil for if he is reacting about 2.5 grams of codeine with about 7grams of pyridine hcl?My research so far tells swim that 220-230 celsius for 5-6 minutes should be ok but could some1 with more knowledge tell swim if this would be correct or if they know a better method to get it spot on and do you guys think the times and temp swim said would come close to getting it correct.thanks in advance Rolling Eyes

bio · Working Bee

You will never be able to hold an even accurate temperature with an electric stove top type heating element especially without a bath as the thermostats simply aren't good enough.

Use an immersion heater (2-300w) and control the temp with a 600w lamp dimmer or better a 5amp fan speed control. This gives decent manual control.

Only the hard frying oil (shortening) has a chance at 230deg and will not last more than a few hours as this is the highest you can go without smoking or catching fire. You MUST use the hard hydrogenated oil, cottonseed if available, at this temp. Regular salad oils will start to smoke around 200deg.