The Benefits of Refluxing - Demonstration

Professor Davis explains why boiling a solution for long periods of time is sometimes necessary, and how chemists accomplish this task without boiling away significant quantities of solvent using the technique of refluxing.

[@Rauchgestein]

Thank you for your professional video. So refluxing is basically boiling something in a pan "with the lid on". Your work helped me, thanks mate :)

[@getmeoutofsanfrancisco9917]

@Jake Obligacion You understood what he meant. What a patronizing response lol.

[@chrisbbbbchris1]

@@getmeoutofsanfrancisco9917 What a degenerate thing to say. He was thanking the guy, get over yourself.

[@ErickvdK]

​@@getmeoutofsanfrancisco9917Ah, San Fransisco, you know all about patronizing then. Let's not go, to San Fransisco!😂

[@geeljireoomaar6140]

Thank you professor Daves. I absolutely enjoyed your informative video. Very clear with step by step demonstration

[@TimeSurfer206]

Right. This is what I would do to make a Syrup from 2C sugar and 1 C water, if it took sugar a day of boiling to dissolve.

[@omarh9410]

Thank you very much, very professional videos.

[@AdriannesWorld]

Great video, professional and educational

[@themainediverschannel4495]

Awesome learning of the proper procedures!!!! And what redux is in a practical application!!!!

[@amiralivalinejad4788]

Thank you, professor Davis!

[@julienguyen7453]

Great video! Can't wait to try

[@srabanidutta617]

it's been so helpful..

[@Omnikam]

Very nice example ❤

[@ma.junalliee.fuentebella-p1319]

MUCH THANKS FOR THIS!!

[@leevanvoon]

thank you very much prof Davis.

[@bayramerdogan121]

Thank you for this great video.

[@raktimroy3797]

Excellent sir..Please make video on experimental strategy to different kinds of organic synthesis...Specially clemension reduction, wolf krishnar etc

[@Aldertonartco]

Shouldn’t you use a reflux condenser instead? Something like a serpentine?

[@nurnajiha3134]

why we cannot fill the flask beyond its half volume?

[@NoctisMotus]

Because of the expansion of the heated substance.

[@Lukelins1]

I can not use vacuum grease when refluxing tallow for the un-saponification. I am measuring how much soap will not be made.

[@almostgrad596]

Great explanation but why the condensing column is opened from above ? are you sure it won't escape ?

[@ChemSurvival]

The opening is to prevent pressure from building as the sample is heated. Refluxing in a closed system is a much more complex and dangerous technique that we typically only use for air sensitive reactions. Loss of solvent through this opening is generally negligible when the technique is performed correctly, but if you have concerns you can substitute for the Liebig condenser I used in the video using something even more efficient like a Dimroth condenser, which is still open, but has even more surface area available in its cooling coil to promote heat exchange (and therefore condensation). I know it seems hard to believe, but you can boil some solutions for hours, days, or even weeks using this simple, open system if it is set up correctly!

[@almostgrad596]

@@ChemSurvival I am really in dept to your help sir. I may ask you one more question which is, if the aliquot of a binary mixture passes through the condenser and it contains the distillate (high volatile) and the other substance (less volatile (BTW what is the proper name for it ?)) why only less volatile component will condense and not the high volatile ?! what is the temperature of that cold water running in the condensing column is it above the boiling point of distillate component so it prevents it from condensing ? sorry for my weird questions but I am wondering a lot.

[@generalingwer4341]

Thanku for video.im just learning.i watched another video on utube and guy was using what looked like a dimroth to me.i could be wrong through.he showed water entering from top of condensor with food color.so maybe im glad i watched this video.not sure??, thanku.

[@cornbread415]

How about comparing the refluxing technique with screwed apparatus, not opened beaker? Are there still advantages for refluxing? That’s my old question.

[@tikatikb]

Thabk you so much. SO helpful!!!

[@bdnugget]

Why on earth would you use grease for ground joints other than in a setup in vacuum. Unnecessary and often gives those nice grease signals on NMR

[@Timothy656]

True, but sometimes depending on the reaction you are carrying out, although typically with strong bases you may get frozen joints, which can be a pain to separate. If you don't mind the idea of risking your ground joints being stuck together when you go to disassemble your apparatus then go right ahead. Personally I find that if you use a tiny bit of grease right at the top of the ground joint you shouldn't get much grease, if any, in your final product when it comes to NMR analysis.

[@ChemSurvival]

Indeed. In my teaching labs, we often perform saponifications and frozen joints were a serious problem until I included this instruction. additionally it's worth noting that with grease, less is more. A small amount can prevent vapor escaping and prevent frozen joints. A large amount can easily end up causing contamination and dominating your NMR spectrum.

[@bdnugget]

Flubberlul around 0.0 - 0.5 ppm as messy aliphatic stuff. When it is silicon based it can even be slightly upfield from 0, like -0.1 ppm

[@bdnugget]

I only seem to get trouble with frozen joints if the joints are wet, especially with water or basic solutions as you guys pointed out. I always make sure the joints are clean and dry before putting it on. Also, just put it on without twisting and turning it while it's fitted. This at least for me ensured this almost never happening anymore.

[@stupaod]

I've recently started distilling using lab equipment and I noticed that my joints were pretty stuck at first. I simply used some hot water on the outside and even a hair dryer seemed to work perfectly to unstick the joint. Is there any reason I should know about, that doing it the way I am could be problematic? Given that its borosilicate glass it seems unlikely that this could be a problem. Application of heat should be fine to unstick them right?

[@alisyed8774]

Wish you could mention the suppliers of this equipment assembly.

[@ShanghaiQIYUIndustrialCompanyM]

f you need lab equipment,we can provide it for you! We are factory outlet and have worked with many laboratories and pharmaceuticamanufacturers.

[@anih3087]

Can you please tell the dilution factor of effluents with hig COD and colour

[@monav2686]

I wish this music wasn't in the background otherwise this is great!

[@shroukrmadan6760]

Thank you

[@omsingharjit]

Thanks

[@137bob3d]

let alone less solvent used how about clearing up an unattended setup like you show us. i think it would be smart to add a thermal probe to the vapors and set a range of operation. say 200 to 215 F. so that an alarm goes off when the vapors are too low or too high. this way casual attention while the lab people tend to other tasks is supplemented by an electronic watchdog.

[@ekbergiw]

I love the clock

[@ChemSurvival]

ME TOO!!!! I made it for my Cafe Press shop here -> www.cafepress.com/chemsurvival

[@roohulamin6839]

Appreciated 👍

[@sandiletsepo6828]

What's that song playing in the background?

[@sawsank3067]

شكرا جزيلا شرح ممتاز

[@aliforeverthere1065]

Thanks alot

[@edgar_faure]

i only need the safrole now.

[@dr.hirakhalid3904]

Keep it up!

[@luv1508]

why do you reflux for 30 minutes?

[@dancalvano8702]

Thanks a tone!

[@137bob3d]

what sort of stuff needs hours and hours to dissolve in a heated solvent ? and when is putting solvent and solute in a untrasonic tank and letting the solvent molecules 'hammer' the solute into solution less bother than refluxing ?

[@wessonsmithjr.6257]

bob along making 5-ATZ(5-Aminotetrazole) which is the precursor two very interesting tetrazole explosives requires two hours of refluxing. So to answer your question that kind of stuff.

[@ThisisFerrariKhan]

MDMA and many other amphetamines. Recreational and Medicinal.

[@HushamALzuhairy]

When refluxing and at high temperatures, is it possible for the grease to melt and descend into the beaker and mix with the liquids?

[@ChemSurvival]

Indeed. One needs to be very careful when using vacuum grease. When it comes to this material, less is more. Too much grease will almost certainly contaminate your samples, but a little bit of Grease can be very helpful. this is particularly true when refluxing aqueous bases like we do in our teaching labs. Without it the hot aqueous base can dissolve small amounts of silica and drposit a cement like material between the joints, effrctively destroying your glassware

[@HushamALzuhairy]

@@ChemSurvival Which is better in terms of use and giving acceptable results in addition to giving thermal homogeneity of the solution? Is it a stirrer device or a water bath or a heating mantle?

[@HushamALzuhairy]

@@ChemSurvival Do you recommend using Teflon instead of Vacuum grease?

[@HushamALzuhairy]

Do you have a special email for inquiries?

[@yanxu9167]

haha your lab coat color is special

[@ChemSurvival]

I have had that coat since graduate school. I fully intend to give my retirement lecture wearing it :-)

[@ankitagaonkar4298]

Super sir

[@pieterscholtz1747]

Clean cold water down the drain ?!

[@SciDOCMBC]

why is everybody using a Liebig condenser, most of the time it's not efficient enough for refluxing, btw vacuum grease is only applied on the upper third of the joint

[@ChemSurvival]

Typically liebig condensers are used because they're cheap, adequate for lower volatility solvents like water and already in the kits for other applications. As for the somewhat liberal application of vacuum grease I teach this to my students because we reflux strong basic solutions during lab which often fuse the glassware together if they are not more liberally greased.

[@SciDOCMBC]

@@ChemSurvival our students also have to use vacuum grease to prevent ground joints from fusing, but we have seen from experience that vacuum grease is distributed very well over the entire joint if you apply enough of it only to the upper third of the joint, if you then put the two joints together and rotate it a few times, it's distributed very well over the whole joint (recognizable by the fact that the joints become transparent over the entire length) this has the advantage that at the lower end of the joint less vacuum grease can be dissolved away and contaminates your solvent, of course, if you use a large amount of solvent anyway, contamination may be irrelevant

[@137bob3d]

at 1+55 you flew right by the time to tell us why replenishing the solvent to 150ml manually is not a choice as it evaporates away. (assuming a fume hood )

[@refaeleranskira1636]

Why would you connect the cold water to the bottom. Makes no sense in this setting! You want to prevent the coash of cold and hot water...am i wrong?

[@mahaelwaseem1900]

who's watching from UB!

[@wordswarsandsymphonies]

me haha what's good

[@lucasjeffrey3580]

God save are queen

[@thomasbetterton4256]

It is better to have flow going from top to bottom and not bottom to top.

[@rafaelecalderon-perez3560]

Thank you, professor Davis!