I am trying to perform a nucleophilic substitution reaction between ditosylated PEG (TsO-PEG-OTs) and phenylenediamine (protected with Boc on one amine). Any suggestions for solvents to use?
You know that PEG can be tosylated using tosyl chloride and a base (such as pyridine) which acts as HCl scavenger.
The tosylated PEG is expected to have –OTs at both ends of the chain. Since each –OTs is attached to 1o carbon, then nucleophilic substitution will be of the SN2 type . Polar aprotic solvents tend to favor SN2 [Examples: DMSO or DMF or acetone or acetonitrile]. DMSO or acetonitrile may be the best but this requires trying.
Please see the attached file which shows the 2 equations of the reaction (Of course Nu: is the amino group of the phenylenediamine). My regards.
I would try acetonitrile first as it is relatively easy to remove and has a good solubility profile. You might want a weak base to mop up the Tosic acid produced but for polymer modification you'll be using the ethylene diamine in fair excess so that might not be necessary.
Dear Kathleen Larson,
Please do not worry about the downvoting of my previous answer. I am used to it. I swear by God that I expected it but I felt that I have to participate since I worked in this field, not particularly on PEG but on similar reactions concerned with polymer analogous conversion or modification involving substitutions & reacting the macromolecules with simple organic compounds in certain media.
This clarification waits another downvoting !
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