Cute story is how NaBH4 was discovered. HC Brown discovered it but by accident by trying to precipitate the salt in acetone. All he got was isopropanol. After that is history
What's most interesting with NaBH4 is that you can fine tune it with catalysts & conditions and get whatever selectivity you want. It's great for esters with the right conditions while still being mild enough not to destroy everything on a sensitive molecule.
I thought the reduction of an epoxide occurs with a ring opening by a nucleophilic attack of a hydride while the aluminium acts as the ring opening Lewis acid. Therefore, my guess would have been that the regioselectivity of the nucleophilic attack depends on the stability of the transition state (Bell-Evans-Polanyi principle) which would be the higher substituted carbocation in the given example. However, regioselectivity can definitely and most of the time is controlled by sterical effects. Why does the reduction of an epoxide with LiAlH4 form the more substituted alcohol? Do sterical effects overweigh the stability of the carbocation?
Your discussion is good but fails to mention the stoichiometries which are different for each given LAH reduction example. In Fieser and Fieser Vol 1 there is a very good discussion on the use of LAH and stoichiometries for your examples. They also cite examples of allylic alcohols being reduced to the corresponding alkanol. Also, there is given their very useful method of work up of a LAH reduction on any scale which gives Al salts as easily filterable solids rather than a gloppy intractable mess. This method is highly recommended as well as the whole series "Reagents for Organic Synthesis" by them. Fieser is pronounced " feezer" . In German the second vowel in the vowel combinations "ie" and "ei" dictates the pronunciation of that vowel combination, so that "ie" is pronounced as "ee" and "ei" is pronounced as "I" . A problem for That Chemist. Using LAH, prepare the Corey intermediate 1,3-dimethylthio-2-propanol from dimethyl disulfide and epichlorohydrin. Show intermediates and all reaction products.
Yeah I should actually know better for the pronunciation of Fieser - I learned German *after* I learned about the Fieser Workup (the way I remember is using the word freitag). We have discussed the Fieser workup in the Discord - if you want to share the resource you are mentioning, I would encourage you to share it in the #resources channel on the Discord!
Hello ,a very nice video , I am currently working with oximes and I couldn't find a way for reducing them till amines by using modified NaBH4 with nanoparticles of Cu however didn't got anything , can you please do a video about reduction of oximes as well as nitriles without using LiAlH4 since its very reactive and needs to be handled with care and plus after blowing after 2 times while preparing Griniard reagent my supervisor told me he wont let me use LiAlH4 and asked me if I could come up with another plan (apart from elctrochemical reduction).
@@jackhinkley6162 no not tried, but since I have furan ring present I doubt whether it would be stable to 5N NH4OH, but thanks for suggestion I would surely try it
One of the best lecture on NaBH4 & LiAlH4.
thanks!
Cute story is how NaBH4 was discovered. HC Brown discovered it but by accident by trying to precipitate the salt in acetone. All he got was isopropanol. After that is history
What's most interesting with NaBH4 is that you can fine tune it with catalysts & conditions and get whatever selectivity you want. It's great for esters with the right conditions while still being mild enough not to destroy everything on a sensitive molecule.
Nice video,
i just did the reduction of cinnamonaldehyd to the cinnamonalkohol with NaBH4 as my first snthesis in the organic chemistry lab course :)
Cool!
I thought the reduction of an epoxide occurs with a ring opening by a nucleophilic attack of a hydride while the aluminium acts as the ring opening Lewis acid. Therefore, my guess would have been that the regioselectivity of the nucleophilic attack depends on the stability of the transition state (Bell-Evans-Polanyi principle) which would be the higher substituted carbocation in the given example. However, regioselectivity can definitely and most of the time is controlled by sterical effects.
Why does the reduction of an epoxide with LiAlH4 form the more substituted alcohol? Do sterical effects overweigh the stability of the carbocation?
Your discussion is good but fails to mention the stoichiometries which are different for each given LAH reduction example. In Fieser and Fieser Vol 1 there is a very good discussion on the use of LAH and stoichiometries for your examples. They also cite examples of allylic alcohols being reduced to the corresponding alkanol. Also, there is given their very useful method of work up of a LAH reduction on any scale which gives Al salts as easily filterable solids rather than a gloppy intractable mess. This method is highly recommended as well as the whole series "Reagents for Organic Synthesis" by them. Fieser is pronounced " feezer" . In German the second vowel in the vowel combinations "ie" and "ei" dictates the pronunciation of that vowel combination, so that "ie" is pronounced as "ee" and "ei" is pronounced as "I" . A problem for That Chemist. Using LAH, prepare the Corey intermediate 1,3-dimethylthio-2-propanol from dimethyl disulfide and epichlorohydrin. Show intermediates and all reaction products.
Yeah I should actually know better for the pronunciation of Fieser - I learned German *after* I learned about the Fieser Workup (the way I remember is using the word freitag). We have discussed the Fieser workup in the Discord - if you want to share the resource you are mentioning, I would encourage you to share it in the #resources channel on the Discord!
Hello ,a very nice video , I am currently working with oximes and I couldn't find a way for reducing them till amines by using modified NaBH4 with nanoparticles of Cu however didn't got anything , can you please do a video about reduction of oximes as well as nitriles without using LiAlH4 since its very reactive and needs to be handled with care and plus after blowing after 2 times while preparing Griniard reagent my supervisor told me he wont let me use LiAlH4 and asked me if I could come up with another plan (apart from elctrochemical reduction).
You could try asking people in the Discord - they are really helpful for this kind of stuff!
@@That_Chemist thanks man
Did you try Zn in AcOH? A workup with at least 5N NH4OH dissolves the Zn salts and the product should be extractable.
@@jackhinkley6162 no not tried, but since I have furan ring present I doubt whether it would be stable to 5N NH4OH, but thanks for suggestion I would surely try it
Criminally low view count on these videos
That probably just means I need to make better lectures
@@That_ChemistModest.