Who can tell me how (S)-4,4-dimethylhexane-3-ol reacts with phosphorus tribromide? If someone actually answers this right I'll go mad
I'm pretty sure the major product would be R-3-Bromo-4,4-dimethyl hexane. Basically with pbr you substitute the alcohol group with a bromine but it causes inversion. If you want I can go over the me mechanism. You should really post questions like these on r/chemhelp in the future. There's some crazy smart people on that subreddit.
that would be awesome! I got stuck on the part where the exchange happens. What I thought happens is the electrons around oxygen attack the phosphorus center causing a bromine to come off, Then the oxygen will be attached to both the hexane and the phosphorus dibromide and it will have a positive charge. After that I thought the lone bromine with a negative charge would come in and attack the carbon atom attached to the oxygen allowing the oxygen to break free from the hexane. Giving a product of OHPBr2 and the new hexane you mentioned. Somewhere in the mechanism I think this is wrong and I can't figure out what it is. Thank you so much for helping me with this!
Remember that after the PBr2 attaches to the oxygen it has a positive charge and makes a good "leaving group". The Br- which left the PBr3 then attacks the carbon which is attached to the oxygen because it has a partial positive charge. This reaction is an SN2 or a substitution reaction which occurs in tandem. This means that the Br- attacks the carbon molecule simultaneously while the HOPBr2 leaves. This causes inversion because the Br- must attack from the opposite end of the leaving group. The reaction is SN2 because Br- is a very strong nucleophile and SN2 reactions can happen on secondary carbons if the nucleophile is not bulky, which Br- is not. Hope that helps explain any confusions you have about PBr3. Let me know if you have any questions about the terminology I used or the concepts.
No haha. I'm currently getting my undergrad degree in Chem and took orgo a couple semesters back. If you have any other questions feel free to pm me or like I said go to r/chemhelp.