In room temperature I guess that is not enough. Use CHCl3 instad of CH2Cl2 and reflux it at 60DegC. Check the TLC using methanol (Only for TLC) If your acid converts to acid chloride, with methanol that will convert to ester. That will show in TLC less polar/non polar than acid. This will be the indication of acid chloride formation.

Sandeep Chandrashekharappa thank you for your insight. I will give it a try.

Synthesis Thionylchloride:

Synthesis of 4-(2-allyloxy)benzoicacyl chloride: 8.9 g of 4-(2-allyloxy)benzoic acid, 15 mL of thionyl chloride were added to a round-bottomed flask equipped with an absorption instrument of hydrogen chloride. The mixture was stirred at room temperature for 4 h, and then heated to 60 °C for 6 h; the excess thionyl chloride was distilled under reduced pressure to give the corresponding acid chloride. Yield: 97%.

4-(allyloxy)benzoyl chloride is prepared next, as follows. To a 100-cm3 round- bottom flask equipped with a reflux condenser, a drying tube, a magnetic stirrer, and a heating bath, is added 50 cm3 (0.42 mol) of freshly-distilled thionyl chloride, into which is dissolved 50 g (0.28 mol) of 4-(allyloxy)benzoic acid with continuous stirring. Ten drops of dimethylformamide are added, the reaction mixture is protected from moisture, and allowed to stir overnight at room temperature. It is then heated to 60PC for an additional 2h to ensure complete reaction. The excess thionyl chloride is removed in vacuo, and the crude product vacuum-distilled at 100°C/1 Torr, yielding 50 g (90%) of a pale yellow liquid which is stored in a tightly-sealed glass container.

Acyl chloride is very reactive species .....u want to confirm then take derivative

First thionyl chloride and Dmf stirred 30 min at 50 temp then add slowly u r aryl acid. Then check tlc 1h.

Acid chlorides are very reactive species and it is very possible (and very likely) that the silica of the TLC (which is slightly acidic) could be hydrolyzing your acid chloride. It is not clear from the TLC results that you reaction did or did not fail--the TLC results are equivocal. They are so reactive that even exposure to ambient atmosphere can hydrolyze them. All solvents and glassware need to be extremely dry (including DMF, which is hydroscopic). So freshly distilled solvents, flame/oven-dried glassware, dry DMF, inert atmosphere, and careful technique are required.

What is your next step? I often do not isolate my acid chloride species and just carry through directly to the next step, keeping the acyl chloride under inert atmosphere the entire time.

Thionyl chloride is a very common reagent, but is also exceptionally toxic. It also generates HCl which may cleave your allyl protecting group. Also common is using isobutyl chloroformate. I have had luck with Ghosez's reagent and strongly recommend that. Also, there are other ways of activating a carboxyl group. Pentafluorophenyl trifluoroacetate can be used to generate the pentafluoropheonl-ester which is highly active (though not as much as an acid chloride) but also air and shelf stable. The PFP ester is also stable on silica gel so you can isolate your activated carboxylic acid if you need too, though again, it is very common to not purify this activated species. There are many, many other approaches.

What do you see on TLC? Only starting materials or new spots? Or consumption or starting materials? And again, have you consider skipping directly to your next step?

I am sure, Simpson has answered most of the questions that might have come in your mind.

Yes, acyl chlorides are normally not isolated and used as such as an intermediate to make the final product.

Just to see the presence of acid chloride itself is not possible on TLC for the reasons Simpson mentioned.

I would take Chandrashekharappa's approach one step further by deliberately adding methanol to a sample of the reaction mass to convert all acid chloride to ester.

This way you can observe the consumption of starting material and formation of ester to confirm presence of acid chloride.

consider no moisture because that hydrolyse acyl chloride back to acid

Grant Simpson thank you very much for your insight. The next step of my experiment will be esterification. I don't think i can skip it directly due to the shortage of chemical that i want in order to synthesis my product.

You could have used Steglich esterification to avoid synthesizing acyl chloride

Jürgen Wintner i used that method before. However, the reaction is not working due to the formation of precipitate.

I agree with Grant Simpson , by the time you have sampled your reaction, dried it onto a silica TLC plate your will have most likely hydrolysed those few milligrams back to the carboxylic acid. Add to this the elution with probably wet solvents in air and you're not going to see any change from starting material.

Reactions with oxalyl chloride (or SOCl2) tend to go very well to completion and it is typical to use a small excess, maybe 1.2 eqv. and then remove your solvent and excess reagent in vacuo, vent with a dry gas, if possible, and use asap.

If you really want to be sure that you have the acid chloride you have two options:

Quench an analytical sample with an alcohol you have on hand (i.e. methanol), be sure this is anhydrous. Then check by TLC to check for loss of starting material, if you're feeling fancy HPLC or LCMS would be good.

Distil the resulting acid chloride, I would guess that your starting material is a solid and the acid chloride is a liquid or low melting solid which you can distil. Doing so would both ensure you have the acid chloride and ensure it is of good purity for your next step. If, as I imagine, you are doing this on a small scale see if you can find a kugelrohr for your distilation.

Dear Tang Xin Ting, You can try this method. Hope it will work well. First of all you have to make the Na-salt of the acid. Treat a suspension or solution of the alkoxybenzoic acid with with a drop of phenolpthalein and then to the stirring solution add a solution of NaOEt (alcoholic NaOH may also serve but in that case it is to be dried thoroughly under vaccum) dropwisely to neutralise it (end point will be light pink with 1-2 drops of NaOEt). Now remove the solvent and dry the Na-Salt of the acid under vaccum or in a descicator. Now suspend this Na-Salt of the alkoxybenzoic acid in dry benzene containing a catalytic amount of dry pyridine and to it add 1.2 equivalent of oxalyl chloride dropwise with stirring protecting from moisture (guard tube to be used). Immediate reaction will take place with formation of precipate of NaCl. Stirr the reaction mixture at r.t for ~2 hours and then at about 60 oC for 15-25 min/ Filter it and the benzene is distilled out carefully protecting from moisture. The acid chloride will be ready for use (it's quite pure for most of the reactions). It's formation can be checked by IR spectral data. The method works very well. In case very pure quality of acid is required, it should be distilled under reduced pressure. Acid chloride of aromatic acids are quite stable (bezoylation of amines or phenols by benzoyl chloride can effectively done in aqueous alkaline medium too!) thus I hope it might be detected by TLC too by activaing the plate at 100 oC for a long time in oven and then carrying out the TLC with dry solvent as developer (say dry benzene or dry pet. ether-EtAc mixture etc) and under inert atmosphere but even then partial decomposition can take place (as correctly mentioned by Grant Simpson). Hence better to check by IR spectral data . I have used this method many times and it gives very good results with high yields.

Hi friend, from your explanations I can understand reaction might be happening and you are not able to see in the TLC. This is because of your acid chloride is highly active and it can react with moister and go back to the acid agin while doing work-up. So for the TLC or conforming the product formation (acid chloride) you can take little and add methanol to that. Methanol will react with acid chloride will give ester and which is stable and distinguishable.

Acid chloride can be hydrolysed in some solvents containing water. What I recommend you to use dry DCM solvent with crude mixture and run your simple in GC-MS to see the peak related with acid chloride. Also if you use acid chloride in another reaction to make whatever, you can use it directly after remove all solvent. Therefore try to use a solvent with less boiling point than DMF. If this doesn't work with you try to use POCl3 instead of oxayl chloride.

On TLC instead of testing the formation of acid chloride, add any protic solvent except water in the reaction mass and check the absence of acid.

hi you can use SOCl2 with DCM to get acid chloride from any acid with high percentage and in dry condition with easy to remove the solvent.

avoid of moisture because that hydrolyse acyl chloride back to acid

Hi, react your acid with thionyl chloride in dichloroethane and reflux it at 75 °C for 8 hrs. Distill off the solvent by using acid trap. you will get acidchloride.