Hi! I would like to ask a few organic chem questions. Preparing for final exam tomorrow :O Any help appreciated?

So,firstly, I would like to add the addition of TFA in Pfitzner Moffat oxidation is to protonate the DCC to form a positive carbocation for the alcohol to attack? Or is there more to it? Why is TFA used and not other acids? Are other acids to weak for this? Secondly, I'd like to ask a question regarding Swern... show more So,firstly, I would like to add the addition of TFA in Pfitzner Moffat oxidation is to protonate the DCC to form a positive carbocation for the alcohol to attack? Or is there more to it? Why is TFA used and not other acids? Are other acids to weak for this?

Secondly, I'd like to ask a question regarding Swern oxidation. Why is the methyl group of the DMSO deprotonated and not directly the red hydrogen atom of the R2-CH-O Bond deprotonated? Shouldnt it be that Oxygen more electronegative ( stronger -I effect) than sulfur and shouldnt that make that corresponding hydrogen atom more acidic? Or is it perhaps that sulfur has a positive charge and therefore acts as a stronger Electrophile that attracts the electrons from Carbon and therefore its Hydrogen groups are more acidic? https://i.stack.imgur.com/nIzuO.png

Lastly for the Collins vs Jones Oxidation, the only discernible differences are the solvent: H2SO4 vs DCM, and that the Collins oxidation makes use of a pyridin chlorochromate, does this complex dampen the oxidative effect of Chromium? So much so that the Collins oxidation can not directly oxidise a alcohol to a carboxylic acid? Whereas Jones reagent with H2sO4 and CrO3 can?
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