I'm trying to react Ar-CL compound (200mg) with a primary amine (1.2 equivalent), and I've found in the literature that they're using a very low amount of solvents (like 0.5ml) to proceed the Ullman coupling; how could this amount dissolve the reactants and the catalysts?
In fact, there're a lot of reactions I've seen being proceeded in a very low amount of solvent, but when I do them in the lab, I use something like 10x of the amount of solvent used in literature as I "feel' that the amount used in literature is very low to dissolve the reactants and the catalysts.
How bad could this affect the rate and the efficiency of the reaction?
I guess they may used vial for reactions. In RB flask generally we can 5 to 40 Volumes of the solvents depending up on the solubility. Usually DMF and DMSO will choose very less or minimum amount of the solvents for reaction.
Sandeep Chandrashekharappa
Thanks for your response, but I still do wonder if they're even using vials to carry out the reaction, how can this 0.5ml of DMSO dissolve all the reactants in a way that allows the reaction to proceed.
I feel that I may have missed an idea.
You can go with minimum volume of solvent in that all your reactants should soluble.
I did the same reaction several times to synthesize different phenazine derivatives. In my case, I was using 1,2 butanediol (2.5mL /gm of reactant). Generally, you can use the 3,5, or 10mL quartz vials for such little solvent reactions.
In general a volume of 10-20 times/the reactant will be chosen for preferential reaction, but in the case of DMSO or DMF small quantity will be adopted to avoid the risk of extraction. However, reports do exist under microwave irradiation where very low solvent quantity will be chosen and vials are specifically manufactured to carryout such reactions at high pressure in short time. Also reports have come out even in neat condition either under magnetic stirring or microwave condition and another way of mortar grinding method etc., Indeed, it is of great concern to find the presence of number of reactive amines (the formed secondary amine also be highly reactive if excess halide will be taken) or other sensitive functional groups which almighty may get influence at such low solvent/high concentration condition to yield other side or by-products. So, better to take normal or high dilution in such cases.
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