I synthesised an amide compound from the reaction between (3-aminophenol and isophthaloyl chloride) in the presence of N,N'-dimethylacetamide as a solvent. After i washed the product with ice-cold deionised water several times to remove the generated HCl, and then recrystallised from hot ethanol and precipitated into ice-cold water again, i got a really pure product, and also a very high yield. However, i need an explanation for the mechanism.
Although I did not use any base to react with the HCl by product, to shift the reaction to product and make it irreversible, the reaction was successful. So what is a reason behind this?
Theoretically, you need base to trap the released HCl. However, if you use excess aminophenol, that itself acts as base and can trap HCl. I think this should help you...
Hi,
the amide which you have as a final product, may act as a scavenger of H+ in its enolate form, till you make the work up (washes with water).
The reaction of an acyl chloride with an amine gives an amide plus HCl. HCl can affect the amide causing undesirable partial hydrolysis which lowers the percentage yield of the amide. If HCl leaves the reaction vessel smoothly or by using an HCl trap or by flushing with dry air , then there is no need for a base in the reaction medium. If HCl is slow to leave, then a weak base such as pyridine or triethylamine is added as "HCl scavanger".
if HCl is going very fast by purging base is not required otherwise you have to use a weak base like TEA
in this reaction solvent has an important role too.....try to change the solvent your reaction would be very slow without any base
two ways for HCl
1st 3-aminophenol acts as self base for quenching of HCl to drive the reaction forward
2nd: due to inert gas purging might loose from the reaction mixture ( it is suspicious)
If amine and acid having enough reactivity, No need any base
An amine reacts fast with an acid chloride. The HCl is possibly trapped by the solvent. The amide once formed will not reverse back in significant extent... It may hydrolise if the reaction conditions are not water-free.
What I think about the equilibrium, is that is driven to the products for 2 reasons:
1. Products are thermodinamically favorable
2. HCl is quenched by the large excess of the acetamide solvent.
I agree with the respected colleagues that HCl might have reacted with N,N-dimethylacetamide as the equation shows:
CH3CON(CH3)2 + H2O + HCl → CH3COOH + (CH3)2NH2+Cl- but this has to be proved because the 2 products are an acid & an acidic salt. We need pH measurement or at least a litmus paper to confirm this path.
Yes Dr. Nizar ,while i washed the product with deionised water, i monitored the pH until became pH=7 and i got a very pure and high percentage of yield.
it is not necessary to use a base to synthesise an amide from the reaction between acyl chloride and an amine.The reaction takes place by stirring or gentle warming.
what happen if we are using trimethoxy benzoyl bromide instead of acyl chloride?
It necessary to use a base to synthesize an amide from the reaction between acyl chloride and an amine as acid is formed during the condensation .
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