Thanks for the advice! The carboxylic acid group is very close to the nanoparticle core and unfortunately I cannot think of a way to extend it without using the EDC/NHS chemistry to couple a amine-peg-(protected COOH). I guess I will try this reaction in anhydrous DMF since the lower polarity may help avoid the competing reaction as you suggested.
Thanks for the advice! The carboxylic acid group is very close to the nanoparticle core and unfortunately I cannot think of a way to extend it without using the EDC/NHS chemistry to couple a amine-peg-(protected COOH). I guess I will try this reaction in anhydrous DMF since the lower polarity may help avoid the competing reaction as you suggested.
One of the main side reactions you will see when using carbodiimides is the formation of the acyl urea. Typically, the more polar the solvent, the faster this side reaction occurs. You can out-compete this by using a stronger nucleophile to attack the activated acid to a certain extent. Its possible though that your acid functionality is too hindered (especially when EDC is attached) to allow for the attack of the amine. Can you use a different solvent system/acid activation method? Or perhaps can you make an analogue with the carboxylic acid extended further from the core of your particles?
One of the main side reactions you will see when using carbodiimides is the formation of the acyl urea. Typically, the more polar the solvent, the faster this side reaction occurs. You can out-compete this by using a stronger nucleophile to attack the activated acid to a certain extent. Its possible though that your acid functionality is too hindered (especially when EDC is attached) to allow for the attack of the amine. Can you use a different solvent system/acid activation method? Or perhaps can you make an analogue with the carboxylic acid extended further from the core of your particles?
More
VOTE
Can you use a different solvent system/acid activation method? Or perhaps can you make an analogue with the carboxylic acid extended further from the core of your particles?
Can you use a different solvent system/acid activation method? Or perhaps can you make an analogue with the carboxylic acid extended further from the core of your particles?
More
VOTE