superhero1219 Posted January 12, 2009 Posted January 12, 2009 I was asked to write the mechanism for a molecule that has an aldehyde group and 2 OH groups in acidic conditions. I'm a bit lost. I will try to link to a picture of what I'm talking about (not sure if it'll work)... http://i163.photobucket.com/albums/t305/superhero1219/shared/ochem-1.jpg The original assignment is in blue. The work I've shown under the assignment is what I think the answer would be if the right side of the molecule wasn't there. If I've made any mistakes, please let me know. I have no clue how to write the mechanism for the full molecule with the 2 OH groups. Can anyone get me started?
UC Posted January 12, 2009 Posted January 12, 2009 (edited) This should be in homework help, but use this: http://www.cem.msu.edu/~reusch/VirtualText/aldket1.htm and scroll down to acetal formation. That online text is very useful for many things. Also, download this program. Your drawings will improve immensely http://www.acdlabs.com/download/chemsk.html For the intermediate step in the middle row, you should draw the carbocationic tautomer, which is the reactive species. Only use one arrow, and it should be obvious that the oxygen in the hydroxy group doing the attacking. For the bottom row, water will not be doing the deprotonating since acetals are made in conditions that remove water, but with acid catalyst. You will see why water removal is necessary when you complete the mechanism. The thing that deprotonates it will be the anion of the H+ earlier in the mechanism. In this way, the acid is regenerated and is a catalyst, not a reactant. I have drawn up the mechanism and will post when I see your full attempt at the mechanism. Edited January 12, 2009 by UC
hermanntrude Posted January 12, 2009 Posted January 12, 2009 UC we're currently not asking people to post homework help in that forum unless they actually want to. Also with only 24 posts under your belt perhaps you shouldn't be telling people where to post what. However, your answer seemed to be in perfect accordance with our usual methods, and also way over my head. good job, keep it up
UC Posted January 19, 2009 Posted January 19, 2009 (edited) Hrm. I don't expect this guy is coming back to check.... Here's the answer if anyone was interested. I left out the tautomers of the carbocation intermediates for simplicity. Edited January 19, 2009 by UC was missing a reaction arrow
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